Microbiology Fundamentals, Chapter 03 – Prokaryotic Cell Structure and Function

Vocabulary flashcards covering terminology from Chapter 3 of Microbiology Fundamentals, focusing on bacterial and archaeal cell structure, function, classification, and clinical relevance.

Cell (cytoplasmic) membrane

Thin lipid-protein bilayer that encloses the cytoplasm and regulates the flow of materials into and out of the bacterial cell.

Cytoplasm

Water-based solution (≈70-80 % water) filling the cell and containing salts, sugars, amino acids, and other building blocks.

Ribosome (70S)

Particle made of rRNA and protein where bacterial protein synthesis occurs; composed of 50S and 30S subunits.

Cytoskeleton

Long protein fibers arranged helically just inside the membrane that help maintain bacterial shape.

Bacterial chromosome / Nucleoid

Single, circular, double-stranded DNA molecule aggregated in a dense region that directs all genetic activities.

Plasmid

Extra-chromosomal, circular DNA that carries non-essential but often advantageous genes such as drug-resistance.

Inclusion body

Cytoplasmic storage granule for nutrients like phosphate, glycogen, or lipids.

Bacterial microcompartment

Protein-coated cytoplasmic packet that concentrates enzymes for specific metabolic pathways.

Endospore

Dormant, highly resistant bacterial structure formed under stress by Bacillus, Clostridium, and relatives.

Vegetative cell

Metabolically active, growing form of a bacterium (contrasts with dormant endospore).

Sporulation

Process by which a vegetative cell forms an endospore in response to adverse conditions.

Germination

Return of a dormant endospore to an actively growing vegetative cell when conditions improve.

Cell wall

Semi-rigid peptidoglycan layer that maintains shape and prevents osmotic rupture.

Peptidoglycan

Macromolecule of alternating N-acetylglucosamine and N-acetylmuramic acid cross-linked by peptides; main component of bacterial cell walls.

Teichoic acid

Polymer embedded in gram-positive walls that reinforces structure and adds negative charge.

Lipoteichoic acid

Teichoic acid variant anchored to the cytoplasmic membrane in gram-positive bacteria.

Outer membrane

Additional lipid bilayer found in gram-negative bacteria, containing lipopolysaccharide and porins.

Lipopolysaccharide (LPS)

Molecule in the gram-negative outer membrane that acts as endotoxin and receptor.

Porin proteins

Outer-membrane channels that allow selective entry of small molecules into gram-negative cells.

S layer

Tightly packed protein monolayer produced under stress for protection or attachment.

Glycocalyx

External polysaccharide or glycoprotein coating that functions in protection, adhesion, and reception.

Slime layer

Loose, easily washed glycocalyx that protects against dehydration and nutrient loss.

Capsule

Dense, well-organized glycocalyx that increases pathogenicity by inhibiting phagocytosis.

Biofilm

Structured microbial community encased in self-produced matrix that adheres to surfaces.

Flagellum

Long, rotating appendage (filament, hook, basal body) that provides motility to bacteria.

Monotrichous

Having a single flagellum at one pole.

Lophotrichous

Having a tuft or cluster of flagella at one pole.

Amphitrichous

Possessing flagella at both poles of the cell.

Peritrichous

Having flagella distributed over the entire cell surface.

Chemotaxis

Directed bacterial movement in response to chemical gradients.

Run (flagellar)

Counterclockwise flagellar rotation that moves the cell in a straight line.

Tumble

Clockwise flagellar rotation causing random change in direction.

Periplasmic flagella / Axial filaments

Internal flagella located between cell wall and membrane of spirochetes, enabling corkscrew motility.

Fimbriae

Short, numerous, hairlike appendages used for tight adhesion to surfaces or host cells.

Pilus (plural pili)

Longer appendage used for conjugation (DNA transfer) and sometimes adhesion in bacteria.

Pleomorphism

Variation in size and shape among cells of a single bacterial species.

Coccus

Spherical or ball-shaped bacterial cell.

Bacillus (rod)

Cylindrical bacterial cell; may be blocky, threadlike, or drumstick-shaped.

Vibrio

Gently curved, comma-shaped rod.

Spirillum

Rigid, helical bacterium with few twists resembling a corkscrew.

Spirochete

Flexible, spring-shaped bacterium possessing periplasmic flagella.

Branching filament

Bacterial form with multiple extensions emerging from a basic rod (e.g., Streptomyces).

Diplococci

Pair of cocci resulting from division in one plane.

Tetrad

Group of four cocci produced by division in two perpendicular planes.

Staphylococci

Irregular clusters of cocci produced by division in multiple planes.

Streptococci

Chains of cocci formed by repeated division in one plane.

Diplobacilli

Pairs of rods with ends attached.

Streptobacilli

Chains of rod-shaped cells.

Palisades

Side-by-side arrangement of bacilli hinged at their ends.

Gram-positive cell wall

Thick (20–80 nm) peptidoglycan layer containing teichoic and lipoteichoic acids; no outer membrane.

Gram-negative cell wall

Thin (1–3 nm) peptidoglycan layer plus an outer membrane with LPS and porins; overall more flexible.

Acid-fast bacteria

Mycobacterium and Nocardia species with waxy mycolic acid–rich walls resistant to dyes and chemicals.

Mycolic acid

Long-chain fatty acid that imparts acid-fast property and pathogenicity to certain bacteria.

Mycoplasma

Bacterium lacking a cell wall; membrane stabilized by sterols; includes M. pneumoniae.

L-form

Wall-deficient variant of bacteria that normally possess a wall; involved in persistent infections.

Extremophile

Organism (often archaeon) that thrives in extreme temperature, pH, or salinity conditions.

Archaea

Prokaryotic domain distinct from Bacteria; possess unique rRNA sequences, lipids, and often extreme habitats.

Bergey’s Manual of Systematic Bacteriology

Reference that classifies bacteria based on phylogeny, especially rRNA sequencing, plus phenotypic traits.

Bergey’s Manual of Determinative Bacteriology

Guide that categorizes bacteria using observable laboratory characteristics for identification.

Gracilicutes

Division of gram-negative bacteria with thin cell walls in Bergey’s taxonomy.

Firmicutes

Division of gram-positive bacteria with thick, strong cell walls.

Tenericutes

Division containing bacteria that lack a cell wall (e.g., Mycoplasma).

Mendosicutes

Division encompassing archaeal groups with unusual walls and metabolisms.

Species (bacterial)

Collection of cells sharing an overall similar pattern of traits and at least 70–80 % genomic similarity.

Strain / Subspecies

Genetically or phenotypically distinct variant within a bacterial species.

Serotype

Subdivision of a species defined by a unique antigenic (antibody-stimulating) pattern.

Lipophilic alcohol swab

Antiseptic that removes lipids from gram-negative outer membranes, enhancing skin disinfection.

Nanowire

Proteinaceous filament used by some bacteria to transfer electrons or communicate within communities.

One Health

Concept emphasizing interconnected health of humans, animals, and the environment.

NCLEX-style question

Assessment format modeled on the nursing licensure exam, integrating microbiology with clinical scenarios.