Microbiology Chapter 4: Prokaryotic Cells and Microorganisms

Vocabulary flashcards covering the characteristics, structures, and classification of prokaryotic cells based on Chapter 4 of Talaro’s Foundations in Microbiology.

Eukaryotic cells

A cell type found in animals, plants, fungi, and protists that contains membrane-bound organelles and a double-membrane bound nucleus.

Prokaryotic cells

A cell type representing bacteria and archaea that lacks a nucleus or other membrane-bound organelles.

Metabolism

The thousands of chemical reactions including chemical and physical life processes that all cells need to function.

Flagellum

A specialized appendage consisting of a filament, hook, and basal body used for motility by rotating $360^{\circ}$.

Monotrichous

A flagellar arrangement featuring a single flagellum located at one end of the cell.

Lophotrichous

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

Amphitrichous

A flagellar arrangement where flagella are located at both ends of the cell.

Peritrichous

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

Chemotaxis

The movement of bacteria in a direction in response to chemical stimuli, which can be positive or negative.

Phototaxis

The movement of bacteria in response to light stimuli.

Fimbriae

Fine, proteinaceous, hairlike bristles emerging from the cell surface that function in adhesion to other cells and surfaces.

Pili

Flexible tubular structures made of pilin protein, found only in gram-negative cells, used for conjugation.

Conjugation

The process where bacterial cells join via a pilus for partial DNA transfer.

Glycocalyx

A surface coating of molecules external to the cell wall made of sugars and/or proteins.

Slime layer

A loosely organized and attached type of glycocalyx that protects cells from dehydration and nutrient loss.

Capsule

A highly organized and tightly attached type of glycocalyx that can inhibit phagocytosis by white blood cells.

Biofilms

Complex aggregations of microbes that form on surfaces, often facilitated by the attachment functions of the glycocalyx.

Peptidoglycan

The primary component of bacterial cell walls, consisting of long glycan chains (NAG and NAM) cross-linked by short peptide fragments.

Gram-positive bacteria

Bacteria with a thick cell wall ($20 \text{ to } 80\,nm$) composed primarily of peptidoglycan and containing teichoic acid.

Gram-negative bacteria

Bacteria with an outer membrane containing lipopolysaccharides, a thin peptidoglycan layer ($8 \text{ to } 11\,nm$), and a periplasmic space.

Teichoic acid

Molecules in gram-positive cell walls that function in wall maintenance and enlargement during cell division.

Lipopolysaccharide (LPS)

A component of the gram-negative outer membrane whose lipid portion acts as an endotoxin toxic to mammals.

Porins

Proteins in the gram-negative outer membrane that regulate the flow of molecules entering and leaving the cell.

Mycolic acid

A lipid or cord factor found in the atypical cell walls of Mycobacterium and Nocardia that contributes to pathogenicity.

Mycoplasmas

Bacteria that lack a cell wall entirely and have a membrane stabilized by sterols, making them pleomorphic.

Fluid mosaic model

A description of the cell membrane structure as a phospholipid bilayer with embedded proteins.

Selective permeability

The property of the cell membrane that regulates the entry of nutrients and the discharge of wastes.

Nucleoid

The central area in a bacterial cell containing the single, circular, double-stranded DNA chromosome.

Plasmids

Small, circular, double-stranded DNA molecules that are not essential for growth but are used in genetic engineering.

Ribosomes

Sites of protein synthesis made of $60\%$ rRNA and $40\%$ protein, with a prokaryotic size of $70S$ ($30S$ and $50S$ subunits).

Inclusions (Granules)

Intracellular storage bodies that store nutrients like fat, phosphate, or glycogen for use when environmental sources are depleted.

Cytoskeleton

An internal network of protein polymers, such as actin filaments, that contribute to the shape of the bacterial cell.

Endospores

Inert, resting cells produced by genera like Bacillus and Clostridium that are highly resistant to heat, radiation, and chemicals.

Sporulation

The process of endospore formation which allows certain bacteria to survive adverse environmental conditions.

Germination

The process by which an endospore returns to its metabolically active vegetative growth state.

Coccus

A spherical-shaped bacterial cell.

Bacillus

A rod-shaped bacterial cell.

Pleomorphism

The ability of some bacterial species to vary in cell shape and size within a single species.

Bergey’s Manual of Systematic Bacteriology

A five-volume resource for classifying all known prokaryotes based on genetic information and phylogenetic relationships.

Archaea

Prokaryotes constituting a distinct domain, often extremophiles, with unique rRNA sequences and membrane lipids with ether linkages.

Extremophiles

Organisms adapted to survive in extreme habitats of temperature, salt, pH, or pressure.

Pseudomonadota

A phylum of gram-negative bacteria containing five classes and over $2,000$ identified species, including E. coli.