Microbiology Chapter 3: Form and Function of Bacteria and Archaea

Vocabulary flashcards covering the structure, shape, arrangement, and classification of bacteria and archaea based on Chapter 3 lecture notes.

Peptidoglycan

A unique chemical component of the bacterial cell wall composed of alternating glycans (N-acetyl glucosamine and N-acetyl muramic acid) and peptide cross-links.

Pleomorphism

Variation in the size and shape of cells of a single species due to nutritional and genetic differences.

Coccus

A bacterial shape described as spherical or ball-shaped, often appearing as perfect spheres, ovals, or bean-shaped variants with an average circumference of $1\,\mu m$.

Bacillus/Rod

A cylindrical bacterial cell shape that can be blocky, spindle-shaped, filamentous, or club-shaped; short and plump versions are called coccobacilli.

Vibrio

A bacterial shape consisting of singly occurring rods that are gently curved.

Spirillum

A bacterium having a slightly curled or spiral-shaped cylinder, forming a rigid helix twisted twice or more along its axis.

Spirochete

A spiral-shaped bacterial cell containing periplasmic flagella that is more flexible than a spirillum and resembles a spring.

Diplococci

An arrangement of cocci where they exist in pairs.

Staphylococci

Irregular clusters of spherical bacteria resembling bunches of grapes.

Streptococci

An arrangement of spherical bacteria formed in chains of variable numbers of cells.

Palisades

An arrangement of bacilli where cells of a chain remain partially attached by a small hinge region at the ends.

Monotrichous

A polar flagellar arrangement consisting of a single flagellum.

Lophotrichous

A flagellar arrangement where small bunches or tufts of flagella emerge from the same site on the cell.

Amphitrichous

A flagellar arrangement where there are flagella at both poles of the cell.

Peritrichous

A flagellar arrangement where flagella are dispersed randomly over the surface of the cell.

Positive Chemotaxis

The movement of bacteria toward a favorable chemical stimulus.

Run

The counterclockwise rotation of flagella resulting in movement in a smooth linear direction.

Tumble

The reversal of the direction of the flagellum (clockwise rotation) causing the cell to stop and change course.

Axial Filaments

Internal flagella (also called periplasmic flagella) enclosed in the space between the cell wall and the cytoplasmic membrane, used for locomotion in spirochetes.

Fimbriae

Fine, hairlike bristles extending from the cell surface that help in adhesion to other cells and surfaces to colonize host tissues.

Pilus

An appendage used for conjugation, drawing another bacterium close in order to transfer DNA; well characterized in gram-negative bacteria.

Glycocalyx

A coating external to the cell wall made of repeating polysaccharide or glycoprotein units; can be a loose slime layer or a tight capsule.

Biofilms

Dense mats of microbes bound together by sticky extracellular deposits that can colonize medical devices like catheters and pacemakers.

Gram-Positive Cell Wall

A thick, homogenous sheet of peptidoglycan ($20 - 80\,nm$ in thickness) that contains teichoic acid and lipoteichoic acid.

Gram-Negative Cell Wall

A single, thin sheet of peptidoglycan ($1 - 3\,nm$ in thickness) that provides flexibility but greater sensitivity to lysis.

Mycolic Acid

A long-chain fatty acid found in the cell walls of acid-fast bacteria like Mycobacterium and Norcardia that contributes to pathogenicity and chemical resistance.

Mycoplasmas

Bacteria that naturally lack a cell wall and use sterols in their cell membrane to stabilize against lysis.

Lipopolysaccharide (LPS)

A component of the gram-negative outer membrane that acts as a signaling molecule and receptor, and is toxic to mammals as an endotoxin.

Porin Proteins

Special membrane channels in the outer membrane that only allow certain chemicals to penetrate.

Plasmids

Nonessential, double-stranded DNA circles containing extra genes that confer traits such as drug resistance or toxin production.

Ribosome (70S)

The site of protein synthesis in bacteria and archaea, composed of a small subunit ($30S$) and a large subunit ($50S$).

Endospore

A dormant body produced by genera like Bacillus and Clostridium that resists extremes of heat, drying, and radiation.

Gracilicutes

A division of bacteria characterized by gram-negative cell walls that are thin.

Firmicutes

A division of bacteria characterized by gram-positive cell walls that are thick and strong.

Tenericutes

A division of bacteria that lack a cell wall and are therefore soft.

Mendosicutes

A division containing archaea, characterized by primitive cells with unusual cell walls and nutritional habits.

Serotype

Representatives of a species that stimulate a distinct pattern of antibody or serum responses.