Envelope

A highly organized glycocalyx layer attached outside the cell wall of some bacteria and fungi, usually built from capsular polysaccharides and retained on the cell surface rather than released as a loose extracellular polymer.

The outermost lipid bilayer of a diderm cell envelope. In canonical Gram-negative bacteria it is asymmetric, with phospholipid enriched in the inner leaflet and lipopolysaccharide enriched in the outer leaflet, and contains beta-barrel proteins that mediate transport and assembly.

The specialized plasma-membrane region that surrounds a cellular bud.

An individual mineralized scale produced by a coccolithophore, with a characteristic arrangement of calcite crystals. Coccoliths form elements of the external cell covering, the coccosphere, and can be shed as free scales.

An external cell covering of a coccolithophore assembled from individual mineralized scales called coccoliths. Its organization varies among taxa and cell states; the covering is distinct from a single coccolith and from the intracellular vesicle in which a coccolith forms.

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.

A porous fungal cell septum in which the cross-wall swells around a central pore and the pore is capped on both sides by septal pore caps called parenthesomes.

A plasma membrane part that is composed of a furrow-like plasma membrane domain and associated integral transmembrane proteins.

A rigid but dynamic carbohydrate- and glycoprotein-rich wall surrounding the fungal plasma membrane, built from a variable cross-linked matrix of glucans, wall glycoproteins, and often chitin and kept distinct from fungal capsules outside the wall.

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

The relatively thin peptidoglycan layer of a Gram-negative cell envelope, located in the periplasm between the cytoplasmic and outer membranes and physically connected to the outer membrane by lipoproteins.

A mycolic-acid-rich cell outer membrane in mycobacteria and related Corynebacteriales, containing a lipid bilayer and covalently linked long-chain mycolic acids attached to peptidoglycan through an arabinogalactan network.

The region between the inner (cytoplasmic or plasma) membrane and outer membrane of organisms with two membranes such as Gram negative bacteria. These periplasmic spaces are relatively thick and contain a thin peptidoglycan layer (PGL), also referred to as a thin cell wall.

A protective, load-bearing structure outside the cytoplasmic membrane, built from glycan strands of alternating N-acetylglucosamine and N-acetylmuramic acid cross-linked by short peptides. The resulting murein sacculus surrounds the cell and resists turgor pressure.

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

The lipid membrane surrounding a cell that separates the cytoplasm from the external environment and houses proteins for selective transport, signaling, and envelope biogenesis.

A paracrystalline monomolecular array of one or more (glyco)protein species that self-assemble on the outermost surface of the cell envelope, with oblique, square or hexagonal lattice symmetry. S-layers are common in Archaea, where they are often the sole wall component, and widespread but patchily distributed in Bacteria.

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.