Chapter 5: Cell Biology of Bacteria

Vocabulary flashcards covering key terms from Chapter 5 notes on bacterial cell biology.

Nucleoid

The region in a prokaryotic cell where the chromosome resides; DNA is double‑stranded, often circular, and not enclosed by a membrane.

70S ribosome

Prokaryotic ribosome consisting of 50S and 30S subunits; site of protein synthesis in bacteria.

80S ribosome

Eukaryotic ribosome consisting of 60S and 40S subunits; not present in bacteria.

Capsule

A neatly organized, firmly attached glycocalyx layer that aids in attachment and protects against phagocytosis.

Slime layer

An unorganized, loose glycocalyx that helps with attachment and biofilm formation.

Glycocalyx

A sugar‑rich coating surrounding some cells, mainly composed of polysaccharides (and sometimes polypeptides).

Teichoic acid

Negatively charged carbohydrate chains in the Gram‑positive cell wall; involved in division, adhesion, and resistance.

Lipoteichoic acid

Teichoic acids anchored to the cell membrane, contributing to wall structure and charge.

Peptidoglycan (PG)

A lattice of glycan chains cross‑linked by short peptides that provides rigidity to bacterial cell walls.

Gram-positive

Bacteria with a thick peptidoglycan layer that retain crystal violet and appear purple after staining.

Gram-negative

Bacteria with a thin peptidoglycan layer and an outer membrane containing LPS; stain pink after counterstain.

Lipopolysaccharide (LPS)

Component of the outer membrane of Gram‑negative bacteria, comprising O antigen, core polysaccharide, and lipid A.

O antigen

Variable outer polysaccharide portion of LPS used for strain identification and host interactions.

Core polysaccharide

Conserved section of LPS shared among related strains.

Lipid A

Endotoxin component of LPS that triggers inflammation via host immune receptors.

Outer membrane (OM)

Outer layer of Gram‑negative bacteria containing LPS and porins; linked to peptidoglycan by lipoproteins.

Porin

Outer membrane channels that allow diffusion of small molecules into Gram‑negative bacteria.

Periplasm

Space between the inner membrane and the outer membrane containing enzymes and transport proteins.

Murein lipoprotein

Lipoprotein that anchors the outer membrane to the peptidoglycan layer in Gram‑negative bacteria.

Mycobacteria

Bacteria with mycolic acid in the cell envelope; resistant to Gram staining and identified by acid‑fast staining.

Mycolic acid

Waxy long‑chain lipids in the cell walls of mycobacteria that contribute to staining characteristics and resistance.

Acid‑fast staining

Staining method used to identify mycobacteria due to their waxy cell walls that resist decolorization.

Mycoplasma

Bacteria that lack a cell wall; have a membrane with sterols; pleomorphic and often cause atypical pneumonia.

Pleomorphic

Ability of a bacterial cell to vary its shape and size.

S‑layer

An external protein lattice that strengthens the cell wall and can aid in immune evasion.

Pili

Filamentous protein structures; fimbriae for attachment and conjugation pili for DNA transfer; may enable twitching motility.

Fimbriae

Short, numerous pili used for attachment to surfaces and biofilms.

Conjugation pilus

A long pilus that facilitates DNA transfer between bacterial cells.

Stalk

A membranous extension of the cytoplasm that secretes adhesion factors for attachment.

Flagellum

Long filament for bacterial motility; composed of flagellin; powered by a proton motive force.

Polar flagella

Flagella located at one or both ends of the cell.

Peritrichous flagella

Flagella distributed around the entire cell surface.

Spirachete

Flexible, spiral‑shaped bacteria; move using endoflagella (axial filament) inside the periplasm.

Endoflagellum (Axial filament)

Flagellar bundle located between outer membrane and peptidoglycan in spirochetes; drives corkscrew motility.

Chemotaxis

Movement toward attractants or away from repellents, often via rotation of flagella.

Endosymbiotic theory

Hypothesis that mitochondria and chloroplasts originated as free‑living bacteria that entered into an symbiotic relationship with early cells.

Mitochondrion

Organelle derived from endosymbiotic bacteria; contains 70S‑like ribosomes and circular DNA.

Chloroplast

Organelle derived from endosymbiotic cyanobacteria; contains 70S ribosomes and circular DNA.

Siderophore

Molecules secreted by bacteria to scavenge iron from the environment.

Secretion system

Multiprotein complexes that export proteins, toxins, and other large molecules; require energy.

Type III secretion system (T3SS)

A secretion system used to inject effector proteins into host cells.

Gas vesicles

Protein‑bound, gas-filled structures that provide buoyancy in aquatic bacteria.

Magnetosome

Magnetite‑containing inclusions enabling magnetotaxis (movement along magnetic fields).

Inclusions

Cytoplasmic storage sites or granules (e.g., sulfur, phosphate) within bacteria.

Pseudomurein

A peptidoglycan‑like polymer found in some archaea, not true peptidoglycan; affects Gram staining reliability.

Archaea (cell walls)

Some archaea have pseudomurein and S‑layers; Gram stain is not informative for many archaea.

Prokaryote

An organism whose cell or cells lack a nucleus. Prokaryotes include both bacteria and archaea

Eukaryote

An organism whose cells contain a nucleus