host peribacteroid membrane

A host-derived membrane that surrounds one or more bacteroids (such as nitrogen-fixing bacteroids within legume root nodule cells).


sculpture element

biolink:CellularComponent biolink:AnatomicalEntity biolink:OrganismalEntity biolink:BiologicalEntity biolink:NamedThing biolink:Entity biolink:PhysicalEssence biolink:SubjectOfInvestigation biolink:ThingWithTaxon biolink:PhysicalEssenceOrOccurrent

The third layer of the sexine.


platelet glycocalyx

The carbohydrate rich layer at the outermost periphery of a platelet.


right tetrad

Set of four basal bodies found in Giardia species (trophozoite stage). It comprises the right lateral basal body pair and the right middle basal body pair (i.e. the anterior, ventral, caudal and posteriolateral basal bodies located to the left of the right nucleus of the trophozoite when viewed dorsally).


ventral disc supernumerary microtubule array

A partial left-handed spiral array of microtubules that lies generally dorsal to the main ventral disc microtubule array in Giardia species (trophozoite stage).


axonemal central pair

Part of the axoneme consisting of the inner two microtubule doublets of the 9+2 axoneme occurring in most motile cilia.


clathrin-coated endocytic vesicle lumen

The volume enclosed by the membrane of a clathrin-coated endocytic vesicle.


early phagosome lumen

The volume enclosed by the membrane of an eary phagosome.


host cell surface

The external part of the host cell wall and/or host plasma membrane.


host apoplast

The apoplast region surrounding a host plant cell. Plants may be described as having two major compartments: the living symplast and the non-living apoplast. The apoplast is external to the plasma membrane and includes cell walls, intercellular spaces and the lumen of dead structures such as xylem vessels. Water and solutes pass freely through it. The host is defined as the larger of the organisms involved in a symbiotic interaction.


organic molecular entity

Any molecular entity that contains carbon.


heteroorganic entity

A heteroorganic entity is an organic molecular entity in which carbon atoms or organic groups are bonded directly to one or more heteroatoms.


organochalcogen compound

An organochalcogen compound is a compound containing at least one carbon-chalcogen bond.


organooxygen compound

An organochalcogen compound containing at least one carbon-oxygen bond.


left ventral basal body

Any ciliary basal body that is part of a left ventral flagellum found in Giardia species (trophozoite stage).


acellular membrane

biolink:AnatomicalEntity biolink:OrganismalEntity biolink:BiologicalEntity biolink:NamedThing biolink:Entity biolink:PhysicalEssence biolink:SubjectOfInvestigation biolink:ThingWithTaxon biolink:PhysicalEssenceOrOccurrent

An acellular anatomical structure that is the bounding layer of a anatomical structure.


endospore-forming forespore

Portion of the cell formed during the process of bacterial sporulation that will ultimately become the core of the endospore. An endospore is a type of dormant cell that is resistant to adverse conditions.


inner layer of spore wall

Either of the two innermost layers of the spore wall, as described in Saccharomyces.


granum

Distinct stack of lamellae seen within chloroplasts. Grana contain the pigments, electron transfer compounds, and enzymes essential to the light-dependent reactions of photosynthesis.


F bouton

Synaptic bouton found in the ventral horn of the spinal cord. F boutons range in diameter from 0.5 to 7 um and contain flattened or pleomorphic synaptic vesicles.


eisosome

A cell part that is composed of the eisosome membrane or MCC domain, a furrow-like plasma membrane sub-domain and associated integral transmembrane proteins, and the proteins (eisosome filaments) that form a scaffolding lattice on the cytoplasmic face. Eisosomes broadly affect overall plasma membrane organization.


Organized structure of distinctive morphology and function, not bounded by a lipid bilayer membrane and occurring outside the cell.


cellulosome

An extracellular multi-enzyme complex containing up to 11 different enzymes aligned on a non-catalytic scaffolding glycoprotein. Functions to hydrolyze cellulose.


mating projection base

The region where the mating projection meets the bulk of the cell, in unicellular fungi exposed to mating pheromone.


apoplast

The cell membranes and intracellular regions in a plant are connected through plasmodesmata, and plants may be described as having two major compartments: the living symplast and the non-living apoplast. The apoplast is external to the plasma membrane and includes cell walls, intercellular spaces and the lumen of dead structures such as xylem vessels. Water and solutes pass freely through it.


porous cell septum

A septum or cross wall which does not entirely span the space between two portions of cell wall and may contain a specialized central pore structure. A porous septum allows the movement of organelles and/or cytoplasm between compartments.


dolipore septum

A septum, or cross-wall, between two portions of a cell or hypha; contains a central pore around which the septum is swollen to form a barrel-shaped structure; pore is covered on each side of the septum by a septal pore cap (parenthosome).


host cell synapse

The junction between a nerve fiber of one host neuron and another host neuron or muscle fiber or glial cell; the site of interneuronal communication.


cellular bud neck septin structure

Any of a series of septin structures that are localized in the bud neck of a budding fungal cell during the cell cycle.


annular furrow extracellular matrix

The extracellular matrix part that is a regularly spaced indentation in the outer cortical layer of the cuticle. The pattern of annular furrows corresponds to sites of invaginations in hypodermal cell membranes that, in turn, correspond to submembranous regions where actin microfilament bundles assemble early in lethargus, the first phase of the molting cycle in which activity and feeding decline.


yolk granule

Discrete structures that partition the water-insoluble portion of the yolk of oocytes and ova, which may or may not be membrane enclosed.


symbiont-containing vacuolar membrane network

Tubular network of extensions from the symbiont-containing vacuole membrane that protrude into the host cytoplasm.


host cell plasma membrane

The plasma membrane surrounding a host cell.


pellicle

The structure enclosing certain parasite cells such as certain apicomplexa and Euglenozoa; consists of the cell membrane with its associated infrastructure of microtubules, microfilaments and other organelles.


dendritic tuft

The terminal specialization found in some types of dendrites which consists of numerous small terminal branches, giving the dendrite a tufted appearance.


peribacteroid fluid

The soluble material inside the peribacteroid membrane, but outside of the bacteroid, within a bacteroid-containing symbiosome.


spine synapse

A type of synapse occurring between an axon and a dendritic spine.


short microvillus layer

A layer of microvilli covering lymphocytes.


proximal convoluted tubule brush border

A brush border layer that is part of a proximal tubule in the kidney.


cellular bud scar

Crater-like ring of chitinous scar tissue located on the surface of the mother cell. It is formed after the newly emerged daughter cell separates thereby marking the site of cytokinesis and septation. The number of bud scars that accumulate on the surface of a cell is a useful determinant of replicative age.


host cell mitochondrial membrane

Either of the lipid bilayers that surround the host cell mitochondrion and form the host cell mitochondrial envelope.


host cell mitochondrial inner membrane

The inner, i.e. lumen-facing, lipid bilayer of the host cell mitochondrial envelope. It is highly folded to form cristae.


exopher

An extracellular vesicle that is approximately four microns in diameter, released by budding out of cells into the extracellular space, and hypothesized to be a mechanism for disposal of unwanted cellular material including protein aggregates and damaged organelles.


female germline ring canal outer rim

An electron opaque backbone of the insect ovarian ring canal that is a part of or adjacent to the plasma membrane. The outer rim is established as the cleavage furrow is arrested, and contains F-actin, anillin, glycoproteins and at least one a protein with a high content of phosphorylated tyrosine residues.


free sarcoplasmic reticulum membrane

The part of the sarcoplasmic reticulum membrane that contains calcium pumps and is devoted to calcium uptake. The free sarcoplasmic reticulum membrane consists of the longitudinal sarcoplasmic reticulum membrane and the non-junctional region of the terminal cisterna membrane.


filiform apparatus

A complex of cell wall invaginations in a synergid cell, similar to those in transfer cells.


endospore core

An intracellular part that represents the innermost portion of an endospore; the endospore core is dehydrated, enriched in dipicolinic acid and divalent cations, and metabolically inactive.


phagocytic cup lip

The tip or margin of the progressing circular lamella that engulfs a particle during phagocytosis. When the two lips of the cup fuse it is converted into a phagosome.


chlorosome envelope

The structure, composed of a monolayer of glycolipids with embedded proteins, that encloses the pigments and other contents of the chlorosome.


organelle-enclosing lipid monolayer

A lipid monolayer that surrounds and encloses an organelle.


microneme

A small, elongated secretory organelle that forms part of the apical complex, located along the main axis of an apicomplexan parasite cell within the extreme apical region and at the periphery under the inner membrane complex. Of the specialized secretory compartments identified in apicomplexans, micronemes discharge their contents first, during initial contact of the parasite's apical pole with the host cell surface. Micronemal proteins function during parasite attachment and penetration into the target cell.


magnetosome

A membrane-bound organelle that envelops particles of magnetic iron minerals in magnetotactic bacteria. Magnetosomes form linear chains that align along the cellular motility axis at midcell and function in bacterial navigation along the Earth's magnetic field. They are formed by invagination of the cell inner membrane; in some species they remain connected to the inner membrane, in others they pinch off to form independent intracellular vesicles.


dinoflagellate epicone

The part of a dinoflagellate cell above the cingulum; also referred to as the anterior portion of a dinoflagellate cell. It is separated from the hypocone by the cingulum.


p-block molecular entity

A main group molecular entity that contains one or more atoms of a p-block element.


chalcogen molecular entity

Any p-block molecular entity containing a chalcogen.


etioplast stroma

The space enclosed by the double membrane of an etioplast but excluding the prothylakoid space. It contains the etioplast DNA.


mating projection

The projection formed by unicellular fungi in response to mating pheromone.


ascus epiplasm

Ascus cytoplasm that is not packaged into ascospores.


phragmosome

A flattened membranous vesicle containing cell wall components.


eyespot apparatus

A small pigmented organelle used in single-celled organisms to detect light.


LYSP100-associated nuclear domain

A nuclear body that is enriched in the lymphoid cell-specific protein LYSp100B; LANDs are globular, electron-dense structures and are morphologically distinct from the annular structures characteristic of PML bodies.


omega speckle

A nucleoplasmic speckle distributed in the interchromatin space of cells in close proximity to chromatin. Omega speckles are distinct from interchromatin granules and contain heterogeneous nuclear RNA-binding proteins (hnRNPs).


nuclear dicing body

A small round nuclear body, measuring 0.2-0.8 microns in diameter that is diffusely distributed throughout the nucleoplasm. Several proteins known to be involved in miRNA processing have been localized to these structures. D-bodies are thought to be involved in primary-miRNA processing and/or storage/assembly of miRNA processing complexes.


sphere organelle

A nuclear body that is found in the germinal vesicles of amphibian oocytes, and consist of three major parts: a remarkably spherical body about 5-10 pm in diameter, smaller spherical or nearly spherical granules on the surface, and inclusions of various sizes that strongly resemble the surface granules. The parts of the sphere organelle have distinct compositions, including splicing snRNAs and proteins.


chromoplast stroma

The space enclosed by the double membrane of a chromoplast but excluding the photosynthetic material.


Golgi apparatus subcompartment

A compartment that consists of a lumen and an enclosing membrane, and is part of the Golgi apparatus.


apical proximal dendrite

The dendrite of the dendritic tree, which emerges near the apical pole of a neuron, and which is the closest to the cell body of the neuron (the soma).


helical viral capsid

The protein coat that surrounds the infective nucleic acid in some virus particles; the subunits are arranged to form a protein helix with the genetic material contained within. Tobacco mosaic virus has such a capsid structure.


germline ring canal

Germline specific intercellular bridge. During cyst formation in insects, ring canals interconnect the cells of the cyst, facilitating the passage of cytoplasmic components between cells.


female germline ring canal

An intercellular bridge that connects the germline cells of a female cyst.


male germline ring canal

An intercellular bridge that connects the germline cells of a male cyst.


vestibular calyx terminal

The giant, cup-shaped axon terminal of a vestibular afferent neuron, serving as a post-synaptic contact to a type I hair cell.


Herring body

The dilated terminal portions of neurosecretory axons constituting the hypothalamohypophyseal tract, found in close proximity to sinusoidal capillaries in the posterior pituitary. Herring bodies consist of aggregates of membrane-bound neurosecretory vesicles where oxytocin or antidiuretic hormone (ADH) are stored prior to release. Each Herring body also contains ATP and either neurophysin I or neurophysin II which bind to oxytocin and ADH, respectively.


P2 peroxisome

A subform of peroxisome that corresponds to an intermediate in a peroxisome assembly pathway, which operates by conversion of peroxisomal subforms in the direction P1, P2 -> P3 -> P4 -> P5 -> P6. P2 peroxisomes are distinguished from the other subforms on the bases of buoyant density and protein content; they are the least dense of the subforms observed.


oral apparatus

Complex basket- or funnel-like structure used by the cell to collect food and channel it to the cytostome; includes specialized sub-structures made up of closely-spaced cilia and underlying basal bodies and fibrillar systems.


cell trailing edge membrane

The portion of the plasma membrane surrounding the trailing edge of a motile cell.


fungal-type vacuole

A vacuole that has both lytic and storage functions. The fungal vacuole is a large, membrane-bounded organelle that functions as a reservoir for the storage of small molecules (including polyphosphate, amino acids, several divalent cations (e.g. calcium), other ions, and other small molecules) as well as being the primary compartment for degradation. It is an acidic compartment, containing an ensemble of acid hydrolases. At least in S. cerevisiae, there are indications that the morphology of the vacuole is variable and correlated with the cell cycle, with logarithmically growing cells having a multilobed, reticulated vacuole, while stationary phase cells contain a single large structure.


reservosome

A large membrane-bound endocytic organelle present only in members of the Schizotrypanum subgenus of the Trypanosoma genus and is defined as the site of storage of endocytosed macromolecules and lysosomal enzymes. It is found at the posterior end of epimastigote forms of Trypanosoma cruzi, but absent in amastigotes and trypomastigotes.


stigma papilla

A plant cell papilla that is part of a stigma papilla cell.


apical lamina of hyaline layer

A fibrous network that is part of the hyalin layer extracellular matrix. The apical lamina is thought to be principally composed of the glycoproteins fibropellins. This matrix has been found in echinoderms.


reservosome membrane

The lipid bilayer surrounding a reservosome.


plasma membrane bounded cell projection

A prolongation or process extending from a cell and that is bounded by plasma membrane, e.g. a cilium, lamellipodium, or axon.


growth cone lamellipodium

A thin sheetlike process extended by the leading edge of an axonal or dendritic growth cone; contains a dense meshwork of actin filaments.


rod spherule

A specialized neuron projection which is the site of synaptic transmission produced by retinal rod cells. Rod spherules are small round enlargements of the axon (3-5 micrometers diameter) or even extensions of the cell body.


giant axon

Extremely large, unmyelinated axon found in invertebrates. Has high conduction speeds and is usually involved in panic or escape responses.


dendritic cell dendrite

A branched cellular projection (or cytoplasmic extension) that is extended from the surface of a dendritic immune cell, and which enables the cell to sample luminal pathogens and increase the surface area for antigen presentation to T cells.


rod telodendria

Rod telodendria are projections that originate from the rod pedicle and form gap junctions with other photoreceptors within the outer plexiform layer of the retina.


accessory outer segment

A cilium-like cell projection emanating from the inner segment and running alongside the outer segment of photoreceptors.


cone telodendria

Cone telodendria are projections that originate from the cone pedicle and form gap junctions with other photoreceptors within the outer plexiform layer of the retina.


muscle cell projection

A prolongation or process extending from a muscle cell. A muscle cell is a mature contractile cell, commonly known as a myocyte. This cell has as part of its cytoplasm myofibrils organized in various patterns.


cytoneme

A long, thin, polarized cell projection that contains actin and can extend for distances many times the diameter of the cell. Cytonemes represent extensions of cell cytoplasm and typically have a diameter of approximately 0.2um.


pollen tube

A tubular cell projection that is part of a pollen tube cell and extends from a pollen grain.


gemmule

Spine-like process found on some neurons, e.g., periglomerular cells of olfactory cortex.


podocyte primary projection

A cell projection originating from a renal glomerular podocyte and extending to the renal glomerular podocyte foot.


rhabdomere microvillus

Thin cylindrical membrane-covered projection on the surface of a rhabdomere.


cell hair

A long, thin cell projection that contains F-actin and tubulin, with microtubules centrally located and F-actin peripherally located.


telodendria

Telodendria are projections that originate from the axon pedicle and form gap junctions with other neurons.


basal proximal dendrite

Any dendrite in a dendritic tree that emerges near the basal pole of a neuron (e.g. in bipolar neurons, basal dendrites are either on the same side of the soma as the axon, or project toward the axon), and which is the closest to the cell body of the neuron (the soma).


rhabdomere

The specialized microvilli-containing organelle on the apical surfaces of a photoreceptor cell containing the visual pigment rhodopsin and most of the proteins involved in phototransduction.


dinoflagellate peduncle

A small, flexible, finger-like projection of cytoplasm containing an array of microtubles and located near the flagellar pores in some photosynthetic as well as nonphotosynthetic dinoflagellate species. Its functions are not fully understood, but it has been associated with feeding behavior (phagotrophy).


plastid

Any member of a family of organelles found in the cytoplasm of plants and some protists, which are membrane-bounded and contain DNA. Plant plastids develop from a common type, the proplastid.


phenyloplast

A chloroplast-derived plastid in which the solid form of phenol is stored.


chloroplast

A chlorophyll-containing plastid with thylakoids organized into grana and frets, or stroma thylakoids, and embedded in a stroma.


apicoplast

The plastid organelle found in apicomplexans.


etioplast

A plastid arrested in the development of chloroplasts from proplastids due to absence of light or low light conditions.


leucoplast

A colorless plastid involved in the synthesis of monoterpenes.


chromoplast

A plastid containing pigments other than chlorophyll, usually yellow and orange carotenoid pigments.


proteinoplast

A leucoplast in which protein is stored.


cyanelle

A plastid that contains unstacked, phycobilisome-bearing thylakoid membranes and is surrounded by a double membrane with a peptidoglycan layer in the intermembrane space between the two envelope membranes. Cyanelles are characteristic of algae in the class Glaucophyta, and may represent an ancestral form of plastid.


cell plate

The nascent cell membrane and cell wall structure that forms between two daughter nuclei near the center of a dividing plant cell. It develops at the equitorial region of the phragmoplast. It grows outwards to join with the lateral walls and form two daughter cells.


egg chorion

A protective, noncellular membrane that surrounds the eggs of various animals including insects and fish.


viral capsid

The protein coat that surrounds the infective nucleic acid in some virus particles. It comprises numerous regularly arranged subunits, or capsomeres.


primary lysosome

A lysosome before it has fused with a vesicle or vacuole.


ascospore-type prospore nucleus

Any nucleus that is part of a ascospore-type prospore.


coated membrane

A single or double lipid bilayer with any of several different proteinaceous coats that can associate with membranes. Membrane coats include those formed by clathrin plus an adaptor complex, the COPI and COPII complexes.


bacterial-type flagellum filament

The long (approximately 20 nm), thin external structure of the bacterial-type flagellum, which acts as a propeller.


dendritic spine origin

The part of the dendritic spine neck where the spine arises from the dendritic shaft.


archaeal-type flagellum

A non-membrane-bounded organelle superficially similar to a bacterial-type flagellum; they both consist of filaments extending outside the cell, and rotate to propel the cell, but the archaeal flagella (also called archaella) have a unique structure which lacks a central channel. Similar to bacterial type IV pilins, the archaeal flagellins (archaellins) are made with class 3 signal peptides and they are processed by a type IV prepilin peptidase-like enzyme. The archaellins are typically modified by the addition of N-linked glycans which are necessary for proper assembly and/or function.


ventral disc overlap zone

A region of the ventral disc of Giardia species (trophozoite stage) where two portions of the same array of microtubules overlap (the microtubule array makes a complete circle and overlaps on itself).


pollen tube tip

The region at growing end of the pollen tube cell, where polarized growth occurs.


extrachromosomal rDNA circle

Circular DNA molecules encoding ribosomal RNA that are replicated independently of chromosomal replication. These molecules originate in the chromosome but are excised and circularized, often by intramolecular homologous recombination between direct tandem repeats.


medial membrane band

A sterol-rich region of the plasma membrane which forms at the cell surface overlying the contractile ring and spreads into the invaginating plasma membrane surrounding the septum.


somatic portion of tanycyte

Portion of a tanycyte that lies within the ependyma and contains the nucleus. A tanycyte is a specialized elongated ventricular ependymal cell that has processes that extend to the outer, or pial, surface of the CNS.


subsynaptic reticulum

An elaborate tubulolamellar membrane system that underlies the postsynaptic cell membrane.


plant cell papilla

A cell projection that is a short, rounded projection from a plant epidermal cell.


tail portion of tanycyte

Elongated process of a tanycyte, devoid of cytoplasmic extensions, that courses through the hypothalamic nuclei to form small endfoot processes that terminate either on blood vessels or at the pial surface of the brain. A tanycyte is a specialized elongated ventricular ependymal cell.


bacterial-type flagellum basal body

One of the three major substructures of the bacterial-type flagellum, the basal body is embedded in the cell envelope (the plasma membrane, peptidoglycan cell wall, and, if one is present, the outer membrane); it houses the secretion apparatus that exports the more distal components and the flagellar motor.


yeast-form cell wall

The wall surrounding a cell of a dimorphic fungus growing in the single-cell budding yeast form, in contrast to the filamentous or hyphal form.


host cell plasmodesma

A fine cytoplasmic channel, found in all higher plants, that connects the cytoplasm of one host cell to that of an adjacent host cell.


contractile actin filament bundle

An actin filament bundle in which the filaments are loosely packed (approximately 30-60 nm apart) and arranged with opposing polarities; the loose packing allows myosin (usually myosin-II) to enter the bundle.


extrahaustorial membrane

The membrane surrounding the symbiont haustorium during symbiosis, derived from the host plasma membrane.


ectexine

The outer part of the exine, which stains positively with basic fuchsin in optical microscopy and has higher electron density in conventionally prepared TEM sections.


periphagosomal region of cytoplasm

Cytoplasm situated near, or occurring around, a phagosome.


actin body

An amorphous cytoskeletal structure consisting of aggregated actin filaments and associated proteins (including fibrin and capping protein) in which there is little or no actin filament turnover. In yeast (S. pombe and S. cerevisiae) these are found only in quiescent cells and are thought to serve as a reserve store of actin.


karyomere

A membrane-bound intermediate cleavage-stage structure of individual or groups of chromosomes that coalesces and fuses with other karyomeres to form a nucleus during interphase. Karyomere formation occurs in blastomeres undergoing rapid cell division.


actin tubule

A cellular structure, approximately 13 nm in diameter, consisting of three actin filaments bundled together.


old cell pole

The cell pole distal from the most recent cell division.


pathogen-containing vacuole membrane

Host-derived membrane of a pathogen-containing vacuole.


bacterial-type flagellum hook

The portion of the bacterial-type flagellum that connects the filament to the basal body.


new cell pole

The cell pole proximal to the most recent cell division.


thylakoid lumen

The volume enclosed by a thylakoid membrane.


mitotic actomyosin contractile ring, intermediate layer

The region of the mitotic actomyosin ring in between the proximal layer and the actin filament layer. This region contains the accessory protein network, some actin filaments and connections between the proximal layer and the actin filament layer.


hemicellulose network

Network composed of hemicelluloses; members of a class of plant cell wall polysaccharide that cannot be extracted from the wall by hot water or chelating agents, but can be extracted by aqueous alkali. Includes xylan, glucuronoxylan, arabinoxylan, arabinogalactan II, glucomannan, xyloglucan and galactomannan.


A membrane-bounded flattened sac that is formed during micropexophagy between the membrane tips of an engulfing vacuole, completing the engulfment and sequestration of peroxisomes from the cytosol, and forming a micropexophagic body within the lumen of the vacuole.


generative cell nucleus

The nucleus of the generative cell, a cell contained within the pollen grain that will divide to produce two haploid sperm cells.


P6 peroxisome

A subform of peroxisome that corresponds to an intermediate in a peroxisome assembly pathway, which operates by conversion of peroxisomal subforms in the direction P1, P2 -> P3 -> P4 -> P5 -> P6. P6 peroxisomes are distinguished from the other subforms on the bases of buoyant density and protein content, and are equivalent to mature peroxisomes.


microtubule organizing center attachment site

A region of the nuclear envelope to which a microtubule organizing center (MTOC) attaches; protein complexes embedded in the nuclear envelope mediate direct or indirect linkages between the microtubule cytoskeleton and the nuclear envelope.


polyadic synapse

A synapse consisting of a single presynapse and multiple postsynapses. These postsynapses may come from the same cell of from different cells. Polyadic synapses are common in arthropod and nematode central nervous systems.


mating projection membrane

The portion of the plasma membrane surrounding a mating projection, the projection formed by unicellular fungi in response to mating pheromone.


methane-oxidizing organelle

A cytoplasmic, membrane-bounded compartment found within Methanotrophic bacteria that contains enzymes and electron transfer proteins for methane catabolism. This structure is analogous to the thylakoid of Cyanobacteria and the anammoxosome of anaerobic ammonium oxidation organisms.


cleavage apparatus septin structure

Any of a series of structures composed of septins and septin-associated proteins localized to the cleavage plane which are involved in cytokinesis.


lytic vacuole within protein storage vacuole

A membrane-bounded compartment containing crystals of phytic acid and proteins characteristic of a lytic vacuole, found within a storage vacuole.


ciliary cap

An intracellular compartmentalized cilium structure found in insect spermatids which is bounded by a membrane derived from the invagination of the cell membrane that remains associated with the primary cilium as it is internalized. The ciliary cap is maintained at the end of the axoneme distal to the centriole and is separated from the cytosolic axoneme/cytoplasm by a putative transition zone, which may extend into the ciliary cap, and include a structure at the base of the ciliary cap termed the ring centriole.


host extracellular space

The space within a host but external to the plasma membrane of host cells, e.g. within host bloodstream.


female germline ring canal inner rim

A proteinaceous actin-rich layer of the insect ovarian ring canal that forms subcortically to the outer rim. The electron dense inner rim accumulates after the final mitotic division of each germline syncytia, and contains actin, a phosphotyrosine protein, and a number of cytoskeletal proteins.


cortical layer of collagen and cuticulin-based cuticle extracellular matrix

The cuticle layer that lies directly beneath the lipid-containing epicuticle. The cortical layer contains collagens and insoluble, non-collagenous cuticulins and is characterized by a distinct annular pattern consisting of regularly spaced annular ridges delineated by annular furrows. An example of this component is found in Caenorhabditis elegans.


ascospore-type prospore

An immature spore undergoing development. The spore usually consists of nucleic acid, prospore membrane(s) that encase the nucleic acid, and ultimately a cell wall that covers the membrane(s). This type of spore is observed in ascospore-forming fungi.


exosporium

The outermost layer of a bacterial endospore, which is loosely attached and located outside of the endospore coat. It is generally composed of protein, carbohydrate, and perhaps lipid.


mitotic actomyosin contractile ring

A cytoskeletal structure composed of actin filaments, myosin, and myosin-associated proteins that forms beneath the plasma membrane of many cells, including animal cells and yeast cells, in a plane perpendicular to the axis of the mitotic spindle, i.e. the cell division plane. Ring contraction is associated with centripetal growth of the membrane that divides the cytoplasm of the two future daughter cells. In animal cells, the mitotic contractile ring is located inside the plasma membrane at the location of the cleavage furrow. In budding fungal cells, e.g. mitotic S. cerevisiae cells, the mitotic contractile ring forms beneath the plasma membrane at the mother-bud neck before mitosis.


multiple synapse bouton

A single axon terminal bouton making contact onto two or more dendritic spines protruding either from a single dendrite or from multiple dendrites.


cellular bud membrane

The portion of the plasma membrane surrounding a cellular bud.


intracellular organelle lumen

An organelle lumen that is part of an intracellular organelle.


microbody lumen

The volume enclosed by the membranes of a microbody.


extracellular core region of desmosome

The desmosomal part containing the desmosomal cadherins, desmogleins and desmocollins, that establish contact and adhere to neighboring cells in a Ca2+-dependent manner.


amyloplast starch grain

Plant storage body for amylose and amylopectin, 1-100um in diameter, and located in amyloplasts. Also contains small amounts of enzymes, amino acids, lipids and nucleic acids. The shape of the grain varies widely amongst species, but is often spherical or disk-shaped.


host cell wall

The rigid or semi-rigid envelope lying outside the host cell membrane of plant, fungal, and most prokaryotic cells, maintaining their shape and protecting them from osmotic lysis. In plants it is made of cellulose and, often, lignin; in fungi it is composed largely of polysaccharides; in bacteria it is composed of peptidoglycan.


plastid intermembrane space

The region between the inner and outer lipid bilayers of the plastid envelope.


mating projection tip membrane

The portion of the plasma membrane surrounding a mating projection tip.


rhabdomere microvillus membrane

The portion of the plasma membrane surrounding a microvillus of a rhabdomere.


spore inner membrane

The membrane surrounding the spore core (endospore core) that separates it from its external environment.


cell wall

The rigid or semi-rigid envelope lying outside the cell membrane of plant, fungal, most prokaryotic cells and some protozoan parasites, maintaining their shape and protecting them from osmotic lysis. In plants it is made of cellulose and, often, lignin; in fungi it is composed largely of polysaccharides; in bacteria it is composed of peptidoglycan; in protozoan parasites such as Giardia species, it's made of carbohydrates and proteins.


host cellular component

Any cellular component of a host cell. The host is an organism in which another organism, for instance a parasite or symbiont, spends part or all of its life cycle and from which it obtains nourishment and/or protection.


mitochondrial inner boundary membrane

The portion of the mitochondrial inner membrane that is not invaginated to form cristae. The inner boundary membrane lies parallel to the outer membrane.


macropinocytic cup cytoskeleton

The part of the cortical actin cytoskeleton that forms part of a macropinocytic cup.


bacterial-type flagellum basal body, MS ring

One of the rings of the bacterial-type flagellar basal body; a double-flanged ring that anchors the basal body to the cytoplasmic membrane.


pilus

A proteinaceous hair-like appendage on the surface of bacteria ranging from 2-8 nm in diameter.


pairing center

A special chromosome region located towards one end of a chromosome that contains dispersed copies of short, repetitive DNA sequences and functions as a cis-acting element essential for presynaptic homologous chromosome pairing and chromosome-nuclear envelope attachment.


nucleomorph

A small, vestigial nucleus found in some plastids that derive from a eukaryotic endosymbiont. Observed in chlorarachniophytes and cryptomonads, which acquired their plastids from a green and red alga respectively.


Gram-positive-bacterium-type cell wall

A layer of peptidoglycan found outside of the cytoplasmic membrane. The peptidoglycan is relatively thick (20-80nm) and retains the primary stain of the Gram procedure, thus cells appear blue after Gram stain. The cell walls often contain teichoic acids (acidic anionic polysaccharides) bound to the peptidoglycan. Examples of this component are found in Gram-positive bacteria.


microsporocyte nucleus

The nucleus of the microsporocyte. The microsporocyte is a diploid cell in which meiosis will occur, resulting in four microspores. A microspore is a spore that, in vascular plants, gives rise to a male gametophyte.


division septum

A cell septum which forms as part of the division site and functions in the compartmentalization of a cell into two daughter cells at division. A division septum spans a cell and does not allow exchange of organelles or cytoplasm between compartments.


ensheathing process

A cell projection (often from glial cells such as Schwann cells) that surrounds an unmyelinated axon or cell soma.


microbody

Cytoplasmic organelles, spherical or oval in shape, that are bounded by a single membrane and contain oxidative enzymes, especially those utilizing hydrogen peroxide (H2O2).


bacterial outer membrane vesicle

A spherical, bilayered proteolipid vesicle released from gram-negative bacterial outer membranes.


type I terminal bouton

Terminal inflated portion of the axon of a glutamatergic neuron, containing the specialized apparatus necessary to release neurotransmitters that will induce the contraction of muscle. The axon terminus is considered to be the whole region of thickening and the terminal bouton is a specialized region of it.


fungal-type cell wall

A rigid yet dynamic structure surrounding the plasma membrane that affords protection from stresses and contributes to cell morphogenesis, consisting of extensively cross-linked glycoproteins and carbohydrates. The glycoproteins may be modified with N- or O-linked carbohydrates, or glycosylphosphatidylinositol (GPI) anchors; the polysaccharides are primarily branched glucans, including beta-linked and alpha-linked glucans, and may also include chitin and other carbohydrate polymers, but not cellulose or pectin. Enzymes involved in cell wall biosynthesis are also found in the cell wall. Note that some forms of fungi develop a capsule outside of the cell wall under certain circumstances; this is considered a separate structure.


multiple synapse bouton, contacting multiple dendrites

A single axon terminal bouton making contact onto two or more dendritic spines protruding from multiple dendrites.


host cell membrane pore complex

Any small opening in a host cell membrane that allows the passage of gases and/or liquids, composed of host proteins.


mitotic nuclear bridge midzone

The central region of a mitotic nuclear bridge, distal to the main portions of the daughter nuclei.


pellicular membrane

The portion of the plasma membrane surrounding the pellicle, a structure enclosing some parasite cells such as certain apicomplexa and Euglenozoa. These membranes are associated with an infrastructure of microtubules, microfilaments, and other organelles.


polytene chromosome ectopic fiber

A thread-like connection joining two regions of ectopically paired polytene chromosomes.


right ventral basal body

Any ciliary basal body that is part of a right ventral flagellum found in Giardia species (trophozoite stage).


microneme membrane

The lipid bilayer surrounding a microneme.


phragmoplast

The phragmoplast is a plant cell specific cytoplasmic structure composed of cytoskeletal polymers, membranes, and associated cytosolic proteins that functions as the focused secretory module for assembling the cell plate.


chloroplast inner membrane

The inner, i.e. lumen-facing, lipid bilayer of the chloroplast envelope; also faces the chloroplast stroma.


envelope

A multilayered structure surrounding all or part of a cell; encompasses one or more lipid bilayers, and may include a cell wall layer; also includes the space between layers.


ventral surface of cell

The surface of a migrating cell that is in contact with the substratum or cell layer.


glycocalyx

A carbohydrate rich layer at the outermost periphery of a cell.


micronucleus

A membrane-bounded organelle of ciliated protozoan cells that contains a diploid copy of the cell's complete genome. Sections of contiguous sequence in the macronucleus are often interrupted by internal eliminated sequences (IES), and may be permuted, in micronuclei. Genic transcription is not found in micronuclei. Some ciliate species may contain multiple micronuclei per cell.


bacterial-type flagellum basal body, proximal rod

The portion of the central rod of the bacterial-type flagellar basal body that is proximal to the cell membrane; the proximal rod connects the distal rod to the flagellar motor.


plant-type cell wall

A more or less rigid stucture lying outside the cell membrane of a cell and composed of cellulose and pectin and other organic and inorganic substances.


chrorion micropyle

A single cone-shaped specialization that forms an opening in the egg chorion that allows sperm entry into the egg prior to fertilization.


pirellulosome

A cytoplasmic structure found in bacterial phyla Planctomycetes and Verrucomicrobia containing a condensed nucleoid and ribosomes and surrounded by an intracytoplasmic membrane. It is surrounded by ribosome-free cytoplasm, in a compartment called the paryphoplasm.


dinoflagellate antapex

The anterior most point of a dinoflagellate hypocone.


glycosome

A membrane-bounded organelle found in organisms from the order Kinetoplastida that houses the enzymes of glycolysis.


plasmodesmatal cytoplasmic sleeve

The space between the plasma membrane and the desmotubule of a plasmodesma.


concave side of sperm head

The concave part of the late spermatid head or spermatozoon head that forms the ventral portion of the head, particularly in some rodent species.


microsporidian-type endospore

The middle layer in a microsporidian spore wall that lies under the exospore and outside the plasma membrane, containing chitin and proteins.


actin wave

A cellular anatomical entity that is part of the actin cytoskeleton and results in a wave-like propagation of actin networks. It consists of dynamic structures traveling on the ventral (substrate-attached) side of the cell during cell migration, cytokinesis, adhesion and neurogenesis.


type II terminal bouton

Terminal inflated portion of the axon of a non-glutamatergic neuron, containing the specialized apparatus necessary to release neurotransmitters at a regulatory synapse. The axon terminus is considered to be the whole region of thickening and the terminal bouton is a specialized region of it.


periarbuscular membrane

A host-derived membrane surrounding the symbiont arbuscule during symbiosis.


dinoflagellate apex

The anterior most point of a dinoflagellate epicone.


symbiont-containing vacuole membrane

The lipid bilayer surrounding a symbiont-containing vacuole, derived from both the host and symbiont.


ciliary microtubule quartet

A set of four specialized microtubules that originates from the basal bodies and wraps around the ciliary pocket membrane, likely supporting its distinct flask shape.


scintillon

A body present in the cytoplasm of some dinoflagellates, which is the source of bioluminescence; emits light on acidification in the presence of oxygen.


P3 peroxisome

A subform of peroxisome that corresponds to an intermediate in a peroxisome assembly pathway, which operates by conversion of peroxisomal subforms in the direction P1, P2 -> P3 -> P4 -> P5 -> P6. P3 peroxisomes are formed by fusion of P1 and P2 peroxisomes, and are distinguished from the other subforms on the bases of buoyant density and protein content.


surface coat of collagen and cuticulin-based cuticle extracellular matrix

An electron dense, amorphous envelope that comprises the outermost layer of the cuticle. The surface coat is loosely apposed to the epicuticle, has distinct biochemical properties, is synthesized by cells other than the underlying hypodermis, and is labile. In addition to serving as a lubricant to protect against abrasion and dehydration, the surface coat may also play important roles in infection and immune evasion. An example of this component is found in Caenorhabditis elegans.


nuclear envelope adjacent to nuclear pore complex

The region of the nuclear envelope situated in close proximity to a nuclear pore complex.


rod photoreceptor disc lumen

The volume enclosed by the membrane of a rod photoreceptor cell disc membrane.


leaflet of membrane bilayer

Any of the two layers of lipid molecules that constitute a membrane.


host cell endomembrane system

A collection of membranous structures involved in transport within the host cell. The main components of the endomembrane system are endoplasmic reticulum, Golgi bodies, vesicles, cell membrane and nuclear envelope. Members of the endomembrane system pass materials through each other or though the use of vesicles. The host is defined as the larger of the organisms involved in a symbiotic interaction.


extrinsic component of periplasmic side of cell outer membrane

The component of the cell outer membrane consisting of gene products and protein complexes that are loosely bound to periplasmic surface, but not integrated into the hydrophobic region.


nucleus leading edge

The area of a motile nucleus closest to the direction of movement.


dendritic knob

The terminal swelling of an apical dendrite of a ciliated olfactory receptor neuron. Each knob gives rise to 5 to 20 long delicate nonmotile cilia, which extend into the mucus covering the sensory epithelium.


chloroplast stroma

The space enclosed by the double membrane of a chloroplast but excluding the thylakoid space. It contains DNA, ribosomes and some temporary products of photosynthesis.


perforation plate

A cell wall part that is the part of a wall of a vessel member and bears one or more openings (perforations).


pathogen-containing vacuole lumen

The enclosed volume within the sealed membrane of a pathogen-containing vacuole.


sperm glycocalyx

The carbohydrate rich layer at the outermost periphery of a sperm cell.


type I pilus

A short filamentous structure on the surface of a bacterial cell distinguished from other pili by their D-mannose-sensitive agglutinatination of erythrocytes. In E. coli, type I pili consist of a short tip fibrillum made up of the adhesin protein (FimH) and two minor subunits (FimG and FimF) that is joined to the pilus rod, a homopolymer of ~1000 FimA subunits.


amyloplast membrane

Either of the lipid bilayers that surround an amyloplast and form the amyloplast envelope.


polytene chromosome weak point

A region of the polytene chromosome where the diameter is considerably decreased, probably resulting from local differences in chromosome organization.


cyanelle stroma

The space enclosed by the double membrane of a cyanelle.


chloroplast membrane

Either of the lipid bilayers that surround a chloroplast and form the chloroplast envelope.


cluster of actin-based cell projections

A cell part consisting of multiple, closely packed actin-based cell projections.


proplastid stroma

The space enclosed by the double membrane of a proplastid.


ciliary shaft

The mid part of a cilium between the ciliary base and ciliary tip that extends into the extracellular space.


intracellular immature spore

A cell or part of the cell that constitutes an early developmental stage of a spore, a small reproductive body that is highly resistant to desiccation and heat and is capable of growing into a new organism, produced especially by certain bacteria, fungi, algae, and nonflowering plants.


rhoptry

A large, club-shaped secretory organelle that forms part of the apical complex of an apicomplexan parasite, and consists of a bulbous body and a narrow electron-dense neck that extends through the conoid at the apical tip of the parasite. The rhoptry necks serve as ducts through which the contents of the rhoptries are secreted after attachment to the host has been completed and at the commencement of invasion. Rhoptry proteins function in the biogenesis and host organellar association of the parasitophorous vacuole.


cortical endoplasmic reticulum lumen

The volume enclosed by the membranes of the cortical endoplasmic reticulum.


gerontoplast stroma

Any plastid stroma that is part of a gerontoplast.


spindle pole body

The microtubule organizing center in fungi; functionally homologous to the animal cell centrosome.


pilus tip

The pointed extremity furthest from the cell of a pilus.


subpellicular network

A mechanically stable cytoskeletal structure associated with the cytoplasmic face of the pellicle and surrounding the microtubule-based cytoskeleton.


hydrogenosome lumen

The volume enclosed by the hydrogenosome membrane.


intermediate layer of spindle pole body

Structure between the central and outer plaques of the spindle pole body.


primary cell wall

A plant cell wall that is still able to expand, permitting cell growth. Primary cell walls contain more pectin than secondary walls and no lignin is present.


S-layer

A crystalline protein layer surrounding some bacteria.


half bridge of spindle pole body

Structure adjacent to the plaques of the spindle pole body.


glycoprotein network

An extracellular matrix part that consists of cross-linked glycoproteins.


acidocalcisome

An electron-dense acidic membrane-bounded organelle which contains a matrix of pyrophosphate and polyphosphates with bound calcium and other cations.


endoplasmic reticulum cisternal network

A subcompartment of the endoplasmic reticulum consisting of flattened, disc-shaped domains known as cisternae. These are typically found close to the nucleus and are generally more prominent in secretory cells.


host cell junction

A plasma membrane part that forms a specialized region of connection between two host cells or between a host cell and the host extracellular matrix. At a host cell junction, anchoring proteins extend through the host plasma membrane to link cytoskeletal proteins in one cell to cytoskeletal proteins in neighboring cells or to proteins in the extracellular matrix.


outer plaque of spindle pole body

One of three laminate structures that form the spindle pole body; the outer plaque is in the cytoplasm.


plastid membrane

Either of the lipid bilayers that surround a plastid and form the plastid envelope.


host cell late endosome membrane

The lipid bilayer surrounding a host cell late endosome.


chloroplast starch grain

Plant storage body for amylose and amylopectin, 1-100um in diameter, and located in chloroplasts. Also contains small amounts of enzymes, amino acids, lipids and nucleic acids. The shape of the grain varies widely amongst species, but is often spherical or disk-shaped.


endexine

The inner part of the exine, which stains.


acroblast

A cone-shaped structure in the head of a spermatozoon, which is formed by the coalescence of Golgi fragments following the completion of meiosis. The acroblast is situated adjacent to the acrosomal vesicle.


haustorium

A projection from a cell or tissue that penetrates the host's cell wall and invaginates the host cell membrane.


organelle

Organized structure of distinctive morphology and function. Includes the nucleus, mitochondria, plastids, vacuoles, vesicles, ribosomes and the cytoskeleton, and prokaryotic structures such as anammoxosomes and pirellulosomes. Excludes the plasma membrane.


inner plaque of mitotic spindle pole body

One of three laminate structures that form the mitotic spindle pole body; the inner plaque is in the nucleus.


extraorganismal space

The environmental space outside of an organism; this may be a host organism in the case of parasitic and symbiotic organisms.


cofilin-actin rod

A cellular structure consisting of parallel, hexagonally arranged actin tubules, comprising filamentous actin and disulfide cross-linked cofilin multimers.


pectic matrix

The gel-like pectin matrix consists of the interlinked acidic and neutral pectin networks that are further cross-linked by calcium bridges. Pectins consist largely of long chains of mostly galacturonic acid units (typically 1,4 linkages and sometimes methyl esters). Three major pectic polysaccharides (homogalacturonan, rhamnogalacturonan I and rhamnogalacturonan II) are thought to occur in all primary cell walls.


bounding membrane of organelle

The lipid bilayer that forms the outer-most layer of an organelle.


acidocalcisome membrane

The lipid bilayer surrounding an acidocalcisome.


organellar chromatophore intermembrane space

The region between the inner and outer lipid bilayers that surround an organellar chromatophore.


type Is terminal bouton

Terminal inflated portion of the axon of a glutamatergic neuron, containing the specialized apparatus necessary for the phasic release neurotransmitters that will induce the contraction of muscle. Type Is terminal boutons are smaller than type Ib terminal boutons.


plasmodesmatal plasma membrane

The portion of the plasma membrane surrounding a plasmodesma.


basal labyrinth

A region in the lower half of some cells formed from extensive infoldings of the basal plasma membrane; includes cytoplasm adjacent to the infolded membrane.


basal layer of collagen and cuticulin-based cuticle extracellular matrix

The layer of cuticle most closely apposed to the hypodermal cells. The morphology of the basal layer varies with life stage. In adult C. elegans animals, the basal layers is comprised of three sublayers: two fibrous layers whose fibers run in clockwise and counter-clockwise directions meeting one another at a 60 degree angle, and an amorphous basal layer that lies underneath the fibrous layers and directly contacts the hypodermis. In C. elegans dauer and L1 larval stage animals, the basal layer is characterized by a striated pattern that appears to derive from interwoven laminae. An example of this component is found in Caenorhabditis elegans.


macronucleus

A membrane-bounded organelle of ciliated protozoan cells that contains polyploid copies of a portion of the cell's complete genome. Transcription of genes occurs in macronuclei. Some ciliate species may contain multiple macronuclei per cell.


ventral disc crossbridge

Structure horizontally linking adjacent microribbons of the ventral disc in Giardia species (trophozoite stage). The composition of crossbridges is not fully known yet.


host cell rough endoplasmic reticulum membrane

The lipid bilayer surrounding the host cell rough endoplasmic reticulum.


host cell endosome membrane

The lipid bilayer surrounding a host cell endosome.


cyanelle intermembrane space

The region between the inner and outer lipid bilayers of the cyanelle envelope; includes the peptidoglycan layer.


longitudinal side of cell surface

The side of the cell parallel to the zygotic axis.


metaphase plate

The intracellular plane, located halfway between the poles of the spindle, where chromosomes align during metaphase of mitotic or meiotic nuclear division.


tectum

The layer of sexine which forms a roof over the columella, granules or other infratectal elements.


type IV pilus

A short filamentous structure on the surface of a bacterial cell distinguished from other pili by post-translational N-methylation of the pilin monomers.


lysosomal glycocalyx

The polysaccharide-based coating on the inner side of a lysosomal membrane. It may be involved in protecting the membrane from digestion by lysosomal enzymes.


fusome

A large intracellular spectrin-rich structure that has been found in insect germline cells and mammalian hematopoietic cells. The fusome is an elongated, branched structure, formed from the spherical spectrosome organelle.


periplasmic space

The region between the inner (cytoplasmic) and outer membrane (Gram-negative Bacteria) or cytoplasmic membrane and cell wall (Fungi and Gram-positive Bacteria).


left tetrad

Set of four basal bodies found in Giardia species (trophozoite stage). It comprises the left lateral basal body pair and the left middle basal body pair (i.e. the anterior, ventral, caudal and posteriolateral basal bodies located to the right of the left nucleus of the trophozoite when viewed dorsally).


cyanelle membrane

Either of the lipid bilayers that surround a cyanelle and form the cyanelle envelope.


bacterial-type flagellum motor

A transmembrane complex embedded in the cytoplasmic membrane which is the motor force, or torque, generator of the bacterial-type flagellum. The motor consists of a membrane-anchored rotor complex surrounded by one or more stator complexes in the cytoplasmic membrane. The stator consists of a hetero-hexameric complex of 2 membrane proteins, A and B, with stoichiometry A4B2. Examples are the H+ driven MotA-MotB stator complex of Escherichia coli and Salmonella enterica, and the Na+ driven PomA-PomB stator complex of Vibrio and Shewanella species. The rotor complex consists of a membrane-anchored ring and the motor switch complex, which controls the direction of flagellar rotation.


extrachromosomal DNA

DNA structures that are not part of a chromosome.


host cell postsynaptic membrane

A postsynaptic membrane that is part of a host cell. A postsynaptic membrane is a specialized area of membrane facing the presynaptic membrane on the tip of the nerve ending and separated from it by a minute cleft (the synaptic cleft). Neurotransmitters transmit the signal across the synaptic cleft to the postsynaptic membrane.


mating projection tip

The apex of the mating projection in unicellular fungi exposed to mating pheromone; site of polarized growth.


spindle envelope

An organelle envelope that surrounds the chromosomes and the central part of the spindle apparatus during mitosis and meiosis; observed in many invertebrates. The spindle envelope consists of membrane layers, called parafusorial membranes, derived from endoplasmic reticulum membrane; in male meiosis it forms during prometaphase and persists until early in the ensuing interphase.


non-growing cell tip

A cell tip at which no growth takes place. For example, in fission yeast the cell end newly formed by cell division does not grow immediately upon its formation, and lacks actin cytoskeletal structures.


starch grain

Plant storage body for amylose and amylopectin, 1-100um in diameter. Also contains small amounts of enzymes, amino acids, lipids and nucleic acids. The shape of the grain varies widely amongst species, but is often spherical or disk-shaped.


host cell smooth endoplasmic reticulum membrane

The lipid bilayer surrounding the host cell smooth endoplasmic reticulum.


photoreceptor proximal connecting cilium

The proximal region of the photoreceptor connecting cilium is similar to the transition zone of unspecialized primary cilia and houses several major transition zone complexes, including NPHP, MKS, and RPGR.


Woronin body

Peroxisome-derived dense-core vesicle that seals septal pores upon hyphal lysis to prevent excessive cytoplasmic loss. It is specific to several genera of filamentous ascomycetes.


meiotic spindle pole body

The microtubule organizing center that forms as part of the meiotic cell cycle; functionally homologous to the animal cell centrosome.


Isp3 layer of spore wall

The outermost layers of the spore wall, as described in Schizosaccharomyces pombe.


spine mat

A configuration of neuron spines found on ciliary ganglion neurons in the embryonic and adult brain consisting of patches of closely spaced spines lying flat against the soma.


DIM/DIP cell wall layer

A section of the Actinobacterium-type cell wall composed of (phenyl)phthiocerol, phthiodiolone, phthiotriol dimycocerosate, diphthioceranate and other compounds.


ciliary pro-basal body

The cilary pro-basal body is an immature, partially assembled form of a ciliary basal body found next to the basal body of a cilium. Pro-basal bodies are not capable of nucleating a cilium. As the cell progresses through the cell cycle, continuing assembly will convert the pro-basal body into a mature basal body that is capable of nucleating a cilium.


plastid stroma

The proteinaceous ground substance of plastids.


rhoptry lumen

The volume enclosed by the rhoptry membrane.


plasma membrane respirasome

A respiratory chain located in the plasma membrane of a cell; made up of the protein complexes that form the electron transport system (the respiratory chain), associated with the plasma membrane. The respiratory chain complexes transfer electrons from an electron donor to an electron acceptor and are associated with a proton pump to create a transmembrane electrochemical gradient.


left posteriolateral basal body

Any ciliary basal body that is part of a left posteriolateral flagellum found in Giardia species (trophozoite stage).


dendriole

Small dendrites that makes up a brush structure found as the terminal specialization of a dendrite of a unipolar brush cell (UBC).


plasma membrane of growing cell tip

Any plasma membrane part that is part of a growing cell tip.


spongiome

A cellular anatomical entity which is a network of tubules and vessicles and is part of the contractile vacuole complex. It is involved in the discharge of water externally. One of its functions is osmoregulatory.


Golgi stack lumen

The volume enclosed by any of the membranes of the thin, flattened cisternae that form the central portion of the Golgi complex.


antipodal cell nucleus

The nucleus of an antipodal cell, one of three cells of the embryo sac in angiosperms, found at the chalazal end of the embryo away from the point of entry of the pollen tube, and its descendents.


pollen wall

The wall surrounding a mature pollen grain; a multilayered structure consisting of a pectocellulosic intine surrounded by a sporopollenin-based exine, which itself contains two layers, the inner nexine and the outer sexine.


host cell part

Any constituent part of a host cell. The host is defined as the larger of the organisms involved in a symbiotic interaction.


cellular bud tip

The end of a cellular bud distal to the site of attachment to the mother cell.


slime layer

A slime layer is an easily removed, diffuse, unorganized layer of extracellular material that surrounds a cell. Specifically this consists mostly of exopolysaccharides, glycoproteins, and glycolipids.


DNA replication termination region

A chromosomal region that contains fork pausing elements influencing the progression and merging of DNA replication forks.


host cell envelope

An envelope that surrounds a bacterial host cell and includes the host cytoplasmic membrane and everything external, encompassing the host periplasmic space, host cell wall, and host outer membrane if present.


satellite fibril

An axoneme part that is found in the flagella of mammalian sperm and is located in the middle piece between the outer dense fibers (on the concave side of outer dense fibers as seen in cross-section).


chitosan layer of spore wall

The second outermost layer of the spore wall, as described in Saccharomyces.


presynaptic grid

A hexagonal array of electron dense particles attached to the cytoplasmic face of the presynaptic membrane.


ciliary pocket collar

A constriction site at the junction of the plasma, flagellar and flagellar pocket membranes where the flagellum emerges from the cell body. Observed in some unicellular eukaryotic species such as Chlamydomonas, Giardia and Trypanosoma.


rod bipolar cell terminal bouton

A specialized region of the axon terminus portion of a rod bipolar axon. A rod bipolar cell is a neuron found in the retina and having connections with rod photoreceptor cells and neurons in the inner plexiform layer.


vascular endothelial glycocalyx

The carbohydrate-rich layer lining the vascular endothelium connected to the endothelium through a variety of molecules, mainly proteoglycans and glycoproteins. These form a network in which soluble molecules, either plasma- or endothelium-derived, are incorporated.


host cell membrane

Double layer of lipid molecules as it encloses host cells, and, in eukaryotes, many organelles; may be a single or double lipid bilayer; also includes associated proteins. The host is defined as the larger of the organisms involved in a symbiotic interaction.


capsule

A protective structure surrounding some fungi and bacteria, attached externally to the cell wall and composed primarily of polysaccharides. Capsules are highly organized structures that adhere strongly to cells and cannot be easily removed. Capsules play important roles in pathogenicity, preventing phagocytosis by other cells, adherance, and resistance to dessication.


bacterial-type flagellum hook-filament junction

The region of the bacterial-type flagellum where the hook and filament meet.


C bouton

Synaptic bouton found in spinal cord on the soma and proximal dendrites of motor neurons.


plastid thylakoid lumen

The volume enclosed by a plastid thylakoid membrane.


sporoplasm

The complex infective apparatus corresponding to the central mass of cytoplasm within a spore that is injected into a host cell by various parasitic microorganisms.


nexine

The inner, non-sculptured part of the exine which lies below the sexine.


ring centriole

A ring-like structure observed at the base of the ciliary cap of insect spermatids. This structure may anchor the axoneme to the ciliary cap membrane and/or act as a diffusion barrier, proposed to be analogous to the annulus of mammalian sperm flagellum.


meiotic actomyosin contractile ring

A cytoskeletal structure composed of actin filaments, myosin, and myosin-associated proteins that forms beneath the plasma membrane of many cells, including animal cells and yeast cells, in a plane perpendicular to the axis of the meiotic spindle, i.e. the cell division plane. Ring contraction is associated with centripetal growth of the membrane that divides the cytoplasm of the two future daughter cells. In animal cells, the meiotic contractile ring is located inside the plasma membrane at the location of the cleavage furrow. In fungal cells, the meiotic contractile ring forms beneath the plasma membrane of the prospore envelope in preparation for completing cytokinesis.


stromule

Thin filamentous structure extending from the surface of all plastid types examined so far, including chloroplast, proplastid, etioplast, leucoplast, amyloplast, and chromoplast. In general, stromules are more abundant in tissues containing non-green plastids, and in cells containing smaller plastids. The primary function of stromules is still unresolved, although the presence of stromules markedly increases the plastid surface area, potentially increasing transport to and from the cytosol. Other functions of stromules, such as transfer of macromolecules between plastids and starch granule formation in cereal endosperm, may be restricted to particular tissues and cell types.


ventral disc lateral crest

Fibrillar repetitive structure surrounding the ventral disc edge in Giardia species (trophozoite stage). The composition of the lateral crest is not fully known yet.


prospore membrane leading edge

The region of the prospore membrane that extends to surround the spore nucleus; coated with specific proteins that are thought to play a role in prospore membrane organization.


smooth muscle dense body

Electron-dense region associated with a smooth muscle contractile fiber.


unicellular trichome branch

A cell projection part that is a branch of a unicellular trichome.


peptidoglycan-based cell wall

A protective structure outside the cytoplasmic membrane composed of peptidoglycan (also known as murein), a molecule made up of a glycan (sugar) backbone of repetitively alternating N-acetylglucosamine and N-acetylmuramic acid with short, attached, cross-linked peptide chains containing unusual amino acids. An example of this component is found in Escherichia coli.


An organelle arrangement comprised of the following elements: a mitochondrion positioned near the presynaptic membrane; an electron-dense mitochondrial plaque adjacent to the outer mitochondrial membrane that faces the presynaptic membrane; filament-like elements appearing to link the mitochondrial plaque to a cell-cell junction region (sometimes termed punctum adherens); tubular or vesicular-appearing membrane (also called vesicular chain) interposed among the filaments. Mitochondrion-associated adherens complexes were initially described in the dorsal horn of the spinal cord. They are found in calyces and other large terminals of the auditory brainstem, and in a variety of mammalian species including humans.


mitochondrial intracristal space

The space bounded by the mitochondrial cristae membranes, continuous with the intermembrane space.


attachment organelle

A membrane-bounded extension of the cell, originally characterized in Mycoplasma species, that contains an electron-dense core that is part of the cytoskeleton and is oriented lengthwise and ends distally in a bulbous knob (terminal button). Required for adherence to host cells and involved in gliding motility and cell division.


cell septum edging

The cell wall material that surrounds the septum in fungal cells.


external encapsulating structure

A structure that lies outside the plasma membrane and surrounds the entire cell or cells. This does not include the periplasmic space.


ventral disc dorsal microribbon

Trilaminar structure extending perpendicularly into the cytoplasm along the length of ventral disc microtubules in Giardia species (trophozoite stage). Constituents of dorsal microribbons (also called dorsal ribbons or microribbons) include alpha-coiled-helix proteins approximately 29 to 38 kDa in size. These proteins line the edges of the microribbons but are not found in microtubules. Tubulins are not found in microribbons.


porosome

A permanent cup-shaped structure at the cell plasma membrane in secretory cells. Following a secretory stimulus, secretory vesicles transiently dock and fuse at the base of porosomes and release intravesicular contents dictated by the turgor pressure generated from the swelling of secretory vesicles.


organelle lumen

The internal volume enclosed by the membranes of a particular organelle; includes the volume enclosed by a single organelle membrane, e.g. endoplasmic reticulum lumen, or the volume enclosed by the innermost of the two lipid bilayers of an organelle envelope, e.g. nuclear lumen.


ectoplasm

Granule free cytoplasm, lying immediately below the plasma membrane.


left middle basal body pair

Set of two basal bodies found in Giardia species (trophozoite stage). It comprises the caudal and posteriolateral basal bodies located to the right of the left nucleus of the trophozoite when viewed dorsally.


median body

A non-membrane bound, semi-organized microtubule array of unknown function found in Giardia species (trophozoite stage). It is located on the dorsal side of the trophozoite, slightly posterior to the ventral disc.


mononeme

A secretory organelle that forms part of the apical complex; a small, threadlike structure located is close proximity to the subpellicular microtubules. Its contents include a rhomboid protease (PfROM1 in Plasmodium falciparum) that moves from the lateral asymmetric localization to the merozoite apical pole and the posterior pole upon release of merozoites from schizonts.


glyoxysome

A specialized form of peroxisome that contains the enzymes of the glyoxylate pathway. The glyoxysome is found in some plant cells, notably the cells of germinating seeds.


preprophase band

A dense band of microtubules, 1-3 pm wide, that appears just beneath the cell membrane before the start of cell division in the cells of higher plants. It precedes the onset of prophase and then disappears as mitosis begins, yet it somehow determines the plane of orientation of the new cell plate forming in late telophase and marks the zone of the parental cell wall where fusion with the growing cell plate ultimately occurs.


inner plaque of spindle pole body

One of three laminate structures that form the spindle pole body; the inner plaque is in the nucleus.


mating projection septin band

A septin band, i.e. a diffuse ring composed of a series of septin bars running parallel to the long axis of the cell, located at the neck of a shmoo (mating projection).


phagocytic cup base

The older part of the phagocytic cup where the actin cytoskeleton disassembles, allowing early incoming and outgoing vesicular trafficking.


apical complex

A group of cytoskeletal structures and associated membrane-bounded organelles found at the anterior end of adult obligate intracellular protozoan parasites in the phylum Apicomplexa. The apical complex is involved in attachment to and penetration of the host cell, and in parasite proliferation.


ocelloid

Eye-like subcellular structure found in dinoflagellates (a large group of single-celled eukaryotes). Consists of subcellular analogues to a cornea, lens, iris, and retina. Ocelloids are built from pre-existing organelles, including a cornea-like layer made of mitochondria and a retinal body made of anastomosing plastids.


exoneme

A dense granule-like organelle of the apical complex of merozoites, released into the parasitophorous vacuole, mediating protease-dependent rupture and parasite exit from the infected erythrocyte.


hyphal membrane

A host-derived membrane surrounding the symbiont hypha during infection.


bacterial-type flagellum filament cap

The proteinaceous structure at the distal tip of the bacterial-type flagellar filament.


magnetosome lumen

The volume enclosed by the membrane of a magnetosome.


primary cell septum

A cell septum that forms following nuclear division.


subplasmalemmal coating

Electron dense material observed coating the cytoplasmic face of the plasma membrane in certain regions of a neuron, e.g., the axon initial segment; the nodal membrane at the Node of Ranvier.


medial cortical node

A component of the cell division site that contains the mid1, cdr2, wee1, klp8, and blt1 proteins, and is involved in contractile ring localization. Medial cortical node complexes appear as cortical dots in the middle of the cell during interphase, and function to recruit other ring components in early mitosis.


reservosome matrix

A matrix composed of planar membranes, vesicles and lipid inclusions within the reservosome.


cortical dynamic polarity patch

A region of the cell cortex that contains a higher concentration of growth polarity factors than the surrounding cortex and that changes position over time. An example is found in fission yeast cells during early mating, in which the GTPase Cdc42 dynamically to discrete zones within the cortex prior to shmoo formation.


centrosomal core

The core region of the centrosome, a layered structure containing proteins, surrounded by the centrosomal corona. The core duplicates once per cell cycle at the G2/M transition when two outer layers form the mitotic spindle poles.


stereocilia coupling link

A structure involved in coupling stereocilia to one another in sensory hair cells There are four morphologically distinct types: tip links, horizontal top connectors, shaft connectors and ankle links. Tip links and horizontal top connectors are the only inter-stereocilia links associated with mature cochlea, whereas ankle links appear during development of the auditory hair bundle.


outer dense plaque of desmosome

The desmosomal part containing plakoglobins, plakophilins, the N-termini of desmoplakins, as well as the cytoplasmic tails of the desmosomal cadherins, which together attach the plaque to the plasma membrane.


organellar chromatophore thylakoid lumen

The volume enclosed by an organellar chromatophore thylakoid membrane.


etioplast membrane

Either of the lipid bilayers that surround a etioplast and form the etioplast envelope.


hyphal cell wall

The cell wall surrounding a fungal hypha.


host intracellular region

That space within the plasma membrane of a host cell.


retrotransposon nucleocapsid

A complex of the retrotransposon RNA genome, reverse transcriptase, integrase, and associated molecules required for reproduction and integration of the retrotransposon into the host genome; the main structural molecule of the nucleocapsid is often a gag protein homolog.


mitochondrial membrane scission site

The site on the mitochondrial membrane where the separation of a single continuous mitochondrial membrane into two membranes occurs as a final step in mitochondrial fission.


acidocalcisome lumen

The volume enclosed by the membranes of an acidocalcisome.


basolateral cytoplasm

The region of the cytoplasm located at the basolateral side of the cell. Used in reference to animal polarized epithelial cells.


deep fiber

Inward projections of the cytoskeletal structures of the oral apparatus, which form a fiber that extends past the cytostome into the cytoplasm.


plant-type vacuole lumen

The volume enclosed within the vacuolar membrane of a vacuole that retains the same shape regardless of cell cycle phase. An example of this is found in Arabidopsis thaliana.


bacterial-type flagellum secretion apparatus

A part of the bacterial-type flagellum that is located at the cytoplasmic side of the MS ring and composed of six membrane proteins (FlhA, FlhB, FliP, FliQ, FliR, and FliO, or orthologs thereof) and three soluble proteins (FliI, FliH, and FliJ, or orthologs thereof) in the cytoplasm. It is responsible for secretion of flagellar type III protein substrates, including the proteins of the flagellar rod, hook, and filament.


annuli extracellular matrix

The extracellular matrix that is a regularly spaced circumferential ridge present in the cortical region of the cuticle. Annuli are delineated by annular furrows and are present throughout the cuticle with the exception of lateral regions where longitudinal alae are present.


basal pole of outer hair cell

The end of the outer hair cell which receives and transmits neural signals.


arbuscule

Highly branched symbiont haustoria within host root cortex cells, responsible for nutrient exchange.


host peribacteroid fluid

The soluble material inside the peribacteroid membrane, but outside of the bacteroid, within a bacteroid-containing symbiosome of a host cell.


plasma membrane of cell tip

The portion of the plasma membrane surrounding the cell tip.


apoptotic body

A vesicle containing parts of a dying cell. Apoptotic bodies can be formed during the execution phase of the apoptotic process, when the cell's cytoskeleton breaks up and causes the membrane to bulge outward. These bulges may separate from the cell, taking a portion of cytoplasm with them, to become apoptotic bodies. These are then engulfed by phagocytic cells, and their components recycled. Apoptotic bodies may range in size from 0.8 to 5um.


host cell endoplasmic reticulum membrane

The lipid bilayer surrounding the host cell endoplasmic reticulum.


mitotic nuclear bridge midzone membrane domain

A nuclear membrane part at the midzone of the mitotic nuclear bridge. The midzone forms a bulge that is enriched in nuclear pores that lack baskets.


microbody membrane

The lipid bilayer surrounding a microbody.


right anterior basal body

Any ciliary basal body that is part of a right anterior flagellum found in Giardia species (trophozoite stage).


extrinsic component of cell outer membrane

The component of the cell outer membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.


central cylinder

A scaffolding structure present within the inner region of the ciliary transition zone. The central cylinder lies between the outer doublet and inner singlet microtubules.


polar nucleus

Either of two nuclei located centrally in a flowering plant embryo sac that eventually fuse to form the endosperm nucleus.


mitotic actomyosin contractile ring, proximal layer

The region of the mitotic actomyosin ring adjacent to the plasma membrane where membrane bound scaffolds are located.


mating projection actin fusion focus

A focus at the mating projection tip where the cell wall is degraded during conjugation with cellular fusion. Actin filaments form an aster-like structure from this location.


external side of cell wall

The side of the cell wall that is opposite to the side that faces the cell and its contents.


early recombination nodule

An electron dense structure that is associated with meiotic chromosomes in leptotene or zygotene during meiosis I.


bacterial-type flagellum basal body, distal rod, L ring

One of the rings of the bacterial-type flagellar basal body; anchors the basal body to the outer membrane.


right posteriolateral basal body

Any ciliary basal body that is part of a right posteriolateral flagellum found in Giardia species (trophozoite stage).


gut granule lumen

The lumen of a gut granule, a lysosome-related organelle contained within the intestinal cells of the nematode C. elegans.


protein storage vacuole lumen

The volume enclosed by the protein storage vacuole membrane.


plasmodesmatal desmotubule

A tightly wound cylinder of membrane that is located within the plasmodesmal pore and runs the length of the plasmodesma. The desmotubule likely provides a rigid stability to plasmodesmata and confers a fixed diameter and pore size to the plasmodesmal canal, and is linked to the endoplasmic reticulum in each of the adjacent cell.


smooth endoplasmic reticulum lumen

The volume enclosed by the membranes of the smooth endoplasmic reticulum.


sexine

The outer, sculptured layer of the exine, which lies above the nexine.


septal periplasm

The region between the plasma membrane and the cell wall, as found in organisms such as filamentous fungi.


noradrenergic synapse

A synapse that uses noradrenaline as a neurotransmitter.


symplast

The interconnected cell membranes and intracellular regions of a plant. The interconnections occur via the plasmodesmata.


endoplasmic reticulum subcompartment

A distinct region of the endoplasmic reticulum.


xanthophore

A chromatophore containing yellow pigment.


secondary cell septum

Cell wall structures composed of linear polysaccharides which are deposited at both sides of the primary septum at 90 degrees to the primary septum.


mitotic nuclear bridge stalk

Either of the regions of a mitotic nuclear bridge proximal to the main portion of each daughter nucleus. The nuclear envelope in the stalk regions is depleted of nuclear pore complexes.


right nucleus

One of the two nuclei found in Giardia species (trophozoite stage). It is located on the right side of the cell when viewed from the dorsal side.


dityrosine layer of spore wall

The outermost layer of the spore wall, as described in Saccharomyces.


yolk

The cytoplasmic part that serves as a nutrient reserve or energy source for the developing embryo.


basal ring of apical complex

An electron dense ring at the most posterior position of the apical complex, from which the subpellicular microtubules originate; formed during an invasive life cycle stage of an apicomplexan parasite.


chromoplast intermembrane space

The region between the inner and outer lipid bilayers of a chromoplast envelope.


basal pole of neuron

Portion of a neuron cell soma closest to the point where the basilar dendrite emerges.


rough endoplasmic reticulum cisterna

A subcompartment of the rough endoplasmic reticulum consisting of lumenal expansion into a flattened, disc-shaped cavity.


mitotic actomyosin contractile ring, distal actin filament layer

The region of the mitotic actomyosin ring containing actin filaments and cross linkers, myosin motors, and connections to the plasma membrane through the intermediate layer. It is further from the plasma membrane than the intermediate layer which it is adjacent to.


organelle envelope lumen

The region between the inner and outer lipid bilayers of an organelle envelope.


dendritic branch point

The part of a dendritic tree where it branches, giving rise to a dendritic branch.


fungal-type vacuole lumen

The volume enclosed within the vacuolar membrane of a vacuole, the shape of which correlates with cell cycle phase. An example of this structure is found in Saccharomyces cerevisiae.


prospore membrane spindle pole body attachment site

The region of the prospore membrane to which the spindle pole body (SPB) is anchored; the prospore membrane extends from the SPB attachment site to surround the spore nucleus.


right middle basal body pair

Set of two basal bodies found in Giardia species (trophozoite stage). It comprises the caudal and posteriolateral basal bodies located to the left of the right nucleus of the trophozoite when viewed dorsally.


medial layer of collagen and cuticulin-based cuticle extracellular matrix

The fluid-filled cuticle layer that lies between the cortical and basal layers and is characterized by the presence of regularly spaced columnar struts that lie on either side of the annular furrows and link the two surrounding layers. In C. elegans, a defined medial layer is found only in adult animals.


cell septum

A structure composed of peptidoglycan and often chitin in addition to other materials. It usually forms perpendicular to the long axis of a cell or hypha and grows centripetally from the cell wall to the center of the cell and often functions in the compartmentalization of a cell into two daughter cells.


host cell presynaptic membrane

A specialized area of membrane of the host axon terminal that faces the plasma membrane of the host neuron or muscle fiber with which the axon terminal establishes a synaptic junction; many host synaptic junctions exhibit structural presynaptic characteristics, such as conical, electron-dense internal protrusions, that distinguish it from the remainder of the axon plasma membrane.


somatic ring canal

A stable intercellular bridge between somatic cells. Examples include the intercellular bridges between ovarian follicle cells in insects and between imaginal disc cells in insects.


type III terminal bouton

Terminal inflated portion of the axon of a non-glutamatergic neuron, containing the specialized apparatus necessary to release neurotransmitters at a regulatory synapse. The axon terminus is considered to be the whole region of thickening and the terminal bouton is a specialized region of it. Type III terminal boutons are larger than type II ones.


bacterial extracellular vesicle

Small membrane vesicle (< 1 um) that buds off a prokaryotic cell plasma membrane, able to carry proteins, phospholipids, lipopolysaccharides, nucleic acids, viruses, and more. Important in intercellular communication and pathogenesis; can exist within host cells.


dinoflagellate antapical horn

A horn-shaped dinoflagellate antapex found in thecate species.


epicuticle of collagen and cuticulin-based cuticle extracellular matrix

A lipid-containing layer of cuticle that lies between the cortical layer and the surface coat. An example of this component is found in Caenorhabditis elegans.


muscle cell postsynaptic specialization

A postsynaptic specialization that is part of a neuromuscular junction.


right lateral basal body pair

Set of two basal bodies found in Giardia species (trophozoite stage). It comprises the anterior and ventral basal bodies located to the left of the right nucleus of the trophozoite when viewed dorsally.


chloroplast thylakoid lumen

The cavity enclosed within the chloroplast thylakoid membrane. An example of this component is found in Arabidopsis thaliana.


cell envelope

An envelope that surrounds a bacterial cell and includes the cytoplasmic membrane and everything external, encompassing the periplasmic space, cell wall, and outer membrane if present.


curli

A proteinaceous extracellular fiber, produced by an enteric bacterium, that is involved in surface and cell-cell contacts that promote community behavior and host colonization.


actin rod

A cellular structure consisting of parallel, hexagonally arranged actin tubules, comprising filamentous actin and associated proteins. Actin rod structures are found in diverse organisms, having been observed in spores of Dictyostelium discoideum, Drosophila melanogaster oocytes, as well as in numerous animal cells under stress conditions.


nucleoplasmic periphery of the nuclear pore complex

Nucleoplasm situated in close proximity and peripheral to a nuclear pore complex.


plastid inner membrane

The inner, i.e. lumen-facing, lipid bilayer of the plastid envelope; also faces the plastid stroma.


organelle subcompartment

A compartment that consists of a lumen and an enclosing membrane, and is part of an organelle.


cellularization cleavage furrow invagination front

The base of the cellularization invagination or cleavage furrow most distal to the original multi-nucleate cell or syncytium plasma membrane.


suberin network

An extracellular matrix part that consists of fatty acid-derived polymers, including both aromatic and aliphatic components. The suberin network is found in specialized plant cell walls, where it is laid down between the primary wall and plasma membrane, forms protective and wound-healing layers, and provides a water-impermeable diffusion barrier.


elaioplast stroma

The space enclosed by the double membrane of an elaioplast.


plant-type vacuole membrane

The lipid bilayer surrounding a vacuole that retains the same shape regardless of cell cycle phase. The membrane separates its contents from the cytoplasm of the cell. An example of this component is found in Arabidopsis thaliana.


prospore contractile ring

A contractile ring, i.e. a cytoskeletal structure composed of actin filaments and myosin, that forms beneath the plasma membrane of the prospore envelope in meiotic cells in preparation for completing cytokinesis.


mesosome

An intracellular, often complex, membranous structure, sometimes with additional membranous lamellae inside, found in bacteria. They are associated with synthesis of DNA and secretion of proteins.


septin band

A diffuse ring composed of a series of septin bars that run parallel to the long axis of the cell. This type of septin structure has been observed in a number of locations associated with polarized grown and/or deposition of new membrane, but not with cytokinesis, such as at the shmoo (mating projection) neck, at the junction between the mother cell and the germ tube (hypha) of a fungal cell growing filamentously.


bacterial-type flagellum basal body, C ring

Cytoplasmic ring located at the base of the bacterial-type flagellar basal body; acts as a rotor; includes three switch proteins, which generate torque and can change their conformational state in a bimodal fashion, so that the motor direction can switch between clockwise and counterclockwise.


extrinsic component of thylakoid membrane

The component of a thylakoid membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.


membrane-enclosed lumen

The enclosed volume within a sealed membrane or between two sealed membranes. Encompasses the volume enclosed by the membranes of a particular organelle, e.g. endoplasmic reticulum lumen, or the space between the two lipid bilayers of a double membrane surrounding an organelle, e.g. nuclear envelope lumen.


cyst wall

The specialized envelope lying outside the cell membrane of a cyst. A cyst is a resting or dormant stage of a microorganism, usually a bacterium or a protist or rarely an invertebrate animal, that helps the organism to survive in unfavorable environmental conditions. In protists such as protozoan parasites alternating cystic- and non-cystic stages, the cyst wall is usually composed of carbohydrates and proteins.


inner membrane pellicle complex

A membrane structure formed of two closely aligned lipid bilayers that lie beneath the plasma membrane and form part of the pellicle surrounding an apicomplexan parasite cell.


orthogonal array

Square array of closely spaced intramembrane particles, 4-6 nm in size, that form supramolecular aggregates found in the plasma membrane of astrocytes, skeletal muscle and epithelial cells. They have been shown to contain aquaporins (water channels).


endospore cortex

A layer surrounding a bacterial endospore found inside the outer endospore membrane, but outside the membrane surrounding the endospore core. It consists of peptidoglycan of a different chemical nature than that found in vegetative cell walls which results in less cross-linking of peptidoglycan.


half bridge of mitotic spindle pole body

Structure adjacent to the plaques of the mitotic spindle pole body.


post-anaphase microtubule array

A cytoskeletal part that consists of an array of microtubules and associated molecules that forms at the end of anaphase, and in which microtubules are nucleated from an equatorial microtubule organizing center.


host cell periplasmic space

The region between the inner (cytoplasmic) and outer host membrane (Gram-negative Bacteria) or inner host membrane and host cell wall (Fungi).


gas vesicle shell

The proteinaceous structure surrounding a gas vesicle.


root hair tip

The tip portion of an outgrowth of a root epidermal cell.


anammoxosome

An intracytoplasmic membrane-bounded compartment in anaerobic ammonium oxidation (anammox) bacteria, is the site of anammox catabolism.


P4 peroxisome

A subform of peroxisome that corresponds to an intermediate in a peroxisome assembly pathway, which operates by conversion of peroxisomal subforms in the direction P1, P2 -> P3 -> P4 -> P5 -> P6. P4 peroxisomes are distinguished from the other subforms on the bases of buoyant density and protein content.


outer plaque of mitotic spindle pole body

One of three laminate structures that form the mitotic spindle pole body; the outer plaque is in the cytoplasm.


extracellular organelle

Organized structure of distinctive morphology and function, occurring outside the cell. Includes, for example, extracellular membrane vesicles (EMVs) and the cellulosomes of anaerobic bacteria and fungi.


host caveola

A small pit, depression, or invagination, such as any of the minute pits or incuppings of the host cell membrane formed during pinocytosis, that communicates with the outside of a host cell and extends inward, indenting the host cytoplasm and the host cell membrane. Such caveolae may be pinched off to form free vesicles within the host cytoplasm. The host is defined as the larger of the organisms involved in a symbiotic interaction.


unicellular trichome apex

A cell projection part that is the apical most portion of a unicellular trichome.


lateral shield

Region of the ventral side of the cell body found in Giardia species (trophozoite stage). It is located posterior on either side of the ventral groove; the upper boundary is the ventral disc, and the lower boundary is marked by the posteriolateral flagella.


plasma membrane-derived chromatophore

A pigment-bearing structure that is derived from the cytoplasmic membrane, sometimes consisting of simple invaginations and sometimes a complete vesicle. This component is found in certain photosynthetic bacteria and cyanobacteria.


organelle envelope

A double membrane structure enclosing an organelle, including two lipid bilayers and the region between them. In some cases, an organelle envelope may have more than two membranes.


ascus membrane

A double layer of lipid molecules that surrounds an ascus, a capsule containing the sexual spores in some fungi.


spine apparatus membrane

The lipid bilayer surrounding the spine apparatus.


synaptonemal structure

A proteinaceous scaffold found between homologous chromosomes during meiosis.


old growing cell tip

A cell tip which has existed for at least one complete cell cycle, and at which polarized growth occurs. For example, in fission yeast the cell end that existed prior to cell division grows immediately after division, and contains a distinctive complement of proteins including actin cytoskeletal structures.


intine

The innermost of the major layers of the pollen grain wall which underlies the exine and borders the cytoplasm.


cellular bud neck

The constriction between the mother cell and daughter cell (bud) in an organism that reproduces by budding.


microsporidian-type exospore

The dense, protein rich outermost layer of a microsporidian spore wall that lies above the endospore.


rDNA protrusion

Any of the tandem arrays of rDNA localized at the periphery of the nucleus and protruding into the nucleolus, and associated proteins. May be visible as a single or double spot by DAPI staining.


microneme lumen

The volume enclosed by the microneme membrane.


Casparian strip

Region of plant cell wall specialised to act as a seal to prevent back leakage of secreted material (analogous to tight junction between epithelial cells). Found particularly where root parenchymal cells secrete solutes into xylem vessels. The barrier is composed of suberin; a fatty substance, containing long chain fatty acids and fatty esters, also found in the cell walls of cork cells (phellem) in higher plants.


rhoptry neck

Narrow, electron-dense part of the rhoptry that extends through the conoid at the apical tip of an apicomplexan parasite. The rhoptry neck serves as a duct through which the contents of the rhoptry are secreted after attachment to the host has been completed and at the commencement of invasion.


podosome core

The F-actin-rich core of an adhesion structure characterized by formation upon cell substrate contact and localization at the substrate-attached part of the cell.


exine

The outer layer of the pollen grain wall which is composed primarily of sporopollenin.


magnetosome membrane

The lipid bilayer surrounding a magnetosome.


conoid

A spiral cytoskeletal structure located at the apical end of the apical complex in some apicomplexan parasites. Fibers form a left-handed spiral, and are comprised of tubulin protofilaments organized in a ribbon-like structure that differs from the conventional tubular structure characteristic of microtubules.


polar ring of apical complex

An electron dense ring at the most anterior position of the apical complex, from which the conoid fibers originate; formed during an invasive life cycle stage of an apicomplexan parasite.


hydrogenosomal membrane

The lipid bilayer surrounding a hydrogenosome.


cleavage furrow leading edge

The 'trough' of the cleavage furrow. This is the part of the cleavage furrow closest to the contractile ring.


external side of fungal-type cell wall

The side of the fungal-type cell wall that is opposite to the side that faces the cell and its contents.