MICROB 3200 Exam Review - Cell Structure and Function Vocabulary

Vocabulary and key concept flashcards for MICROB 3200 Exam Review covering bacterial cell structure, envelope components, cytoskeletal proteins, and key bacterial taxa.

Domain

The broadest taxonomic rank; the three domains are Archaea, Bacteria, and Eukarya.

Taxonomy

The formal system used to classify and name organisms, increasingly based on evolutionary relationships, genetics, and shared ancestry.

Prokaryote

A unicellular organism whose DNA occupies a nucleoid and that lacks a nucleus and other membrane-bound organelles.

Nucleoid

The organized, non-membrane-bound region containing the bacterial chromosome and associated DNA-binding and regulatory proteins.

Cell Envelope

The layers surrounding bacterial cytoplasm, including the cytoplasmic membrane, cell wall, and - in Gram-negative bacteria - the outer membrane.

Periplasm

The compartment between the inner and outer membranes of Gram-negative bacteria; it contains the thin peptidoglycan layer and various proteins.

Nucleoid-Associated Proteins (NAPs)

Proteins that bind, loop, organize, and compact bacterial chromosomal DNA.

Endospore

A dormant, tough, non-reproductive survival structure that is highly resistant to heat, drying, radiation, and disinfectants.

Phospholipid

An amphipathic membrane molecule with a hydrophilic phosphorylated head and two hydrophobic fatty-acid tails.

Hydrophilic

Attracted to or able to interact with water; phospholipid heads face the aqueous environment.

Hydrophobic

Water-repelling; phospholipid fatty-acid tails cluster inside the membrane bilayer.

Membrane Fluidity

The ability of membrane lipids and proteins to move within the bilayer; influenced strongly by temperature and fatty-acid saturation.

Sacculus

The single, continuous, cage-like peptidoglycan cell wall that surrounds and supports the bacterial membrane.

Peptidoglycan (PG)

A rigid cell-wall polymer of alternating NAG and NAM sugars cross-linked by short peptide bridges.

N-acetylglucosamine (NAG)

One of the two alternating amino sugars that form the glycan backbone of peptidoglycan.

N-acetylmuramic acid (NAM)

The peptidoglycan amino sugar that alternates with NAG and carries the short peptide used for cross-linking.

Monoderm

A cell-envelope plan with one membrane; used here for Gram-positive bacteria with thick peptidoglycan and no outer membrane.

Diderm

A cell-envelope plan with two membranes; used here for Gram-negative bacteria with inner and outer membranes.

Teichoic Acid

A polymer in Gram-positive cell walls that helps organize thick peptidoglycan and protect against chemical insults.

Lipopolysaccharide (LPS)

A Gram-negative outer-membrane molecule composed of O antigen, core, and Lipid A; also called endotoxin.

Endotoxin

Another name for LPS; especially associated with the inflammatory effects of its Lipid A component.

O Antigen

The highly variable, repeating sugar portion of LPS that differs among bacterial groups and can be used for identification.

Lipid A

The hydrophobic LPS component that anchors LPS in the outer membrane and drives strong inflammatory toxicity.

Porin

An outer-membrane channel that allows small hydrophilic molecules to diffuse into the Gram-negative periplasm.

Capsule

A firmly anchored, organized extracellular layer, usually polysaccharide, that promotes adherence and protects against phagocytosis.

Slime Layer

A loose, diffuse extracellular polysaccharide layer that promotes adherence and often gives colonies a wet or mucoid appearance.

Flagellum

A long, helical, rotating appendage that propels a bacterial cell.

Pilus / Fimbria

A short, hair-like surface appendage used mainly for attachment; specialized pili can transfer DNA.

Sex Pilus

A specialized pilus that connects bacterial cells and enables transfer of DNA between them.

Acid-fast Stain

A special staining procedure used to visualize bacteria such as Mycobacterium tuberculosis that do not stain reliably with the Gram stain.

Three Domains of Life

Archaea, Bacteria, and Eukarya, revealed largely through comparisons of small-subunit ribosomal RNA sequences (16S rRNA in prokaryotes).

Bacterial Cell Size

Typically about $0.2\text{--}2\text{ micrometers}$ in diameter, compared to a human hair which is about $50\text{--}100\text{ micrometers}$ wide.

FtsZ

A bacterial cytoskeletal protein that forms the Z-ring for cell division and helps maintain cell diameter.

MreB

A bacterial cytoskeletal protein that supports the elongation of rod-shaped cells.

CreS (Crescentin)

A bacterial cytoskeletal protein that polymerizes along the inner curve of crescent-shaped cells.

Bacillota

A Gram-positive bacterial group classically associated with endospore formation, specifically including Bacillus species and Clostridium species.

Clostridium botulinum

A Gram-positive, anaerobic, rod-shaped, motile, spore-forming bacterium whose neurotoxin causes flaccid paralysis.

Clostridium tetani

A Gram-positive, anaerobic, rod-shaped, motile, spore-forming bacterium whose neurotoxin causes spastic paralysis.

Mycoplasma pneumoniae

A bacterium associated with walking pneumonia that lacks a cell wall, has no peptidoglycan target, and is inherently resistant to beta-lactam antibiotics.

Streptococcus pneumoniae

A lancet-shaped diplococcus whose polysaccharide capsule serves as a major virulence factor.

LPS Core

The conserved region of lipopolysaccharide (LPS) that helps the bacterial outer membrane resist detergents.