Chapter 4: A Survey of Prokaryotic Cells and Microorganisms

Vocabulary flashcards covering Chapter 4: A Survey of Prokaryotic Cells and Microorganisms.

Eukaryotic Cell

A cell type found in animals, plants, fungi, and protists that contains membrane-bound organelles compartmentalizing the cytoplasm and a double-membrane-bound nucleus containing DNA chromosomes.

Prokaryotic Cell

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

Flagellum

A specialized appendage attached to the cell by a basal body holding a long, rotating filament that rotates $360^\text{o}$ to push the cell forward and provide motility.

Flagellin

The protein that composes the long, thin, helical filament structure of a bacterial flagellum.

Monotrichous

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

Lophotrichous

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

Amphitrichous

A flagellar arrangement featuring flagella attached at both ends of the cell.

Peritrichous

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

Chemotaxis

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

Phototaxis

The movement of a cell in response to light stimuli.

Run (Flagellar Movement)

Smooth linear direction movement of a cell resulting from counterclockwise flagellar rotation.

Tumble (Flagellar Movement)

Stopping and random changing of direction by a cell caused by clockwise flagellar rotation.

Periplasmic Flagella

Internal flagella (axial filaments) enclosed between the outer sheath and cell wall peptidoglycan that contract to produce a twisting or flexing motion.

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, that function to join bacterial cells for partial DNA transfer called conjugation.

Glycocalyx

A coating of molecules (sugars and/or proteins) external to the cell wall that functions in protection, adhesion, and reception.

Slime Layer

A loose, unorganized glycocalyx structure that protects cells from dehydration and loss of nutrients.

Capsule

A highly organized, tightly attached glycocalyx coating that protects bacteria from phagocytosis by white blood cells, contributing to pathogenicity.

Peptidoglycan

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

Teichoic Acid

An acidic polymer found in Gram-positive cell walls that functions in cell wall maintenance and enlargement during division and stimulates an immune response.

Lipopolysaccharide (LPS)

A lipid and carbohydrate complex found in the outer membrane layer of Gram-negative bacteria whose lipid portion acts as an endotoxin toxic to mammals.

Porin Proteins

Proteins in the upper layer of the Gram-negative outer membrane that form channels to regulate the entry and exit of molecules.

Gram Stain

A differential staining procedure that classifies bacteria into Gram-positive (purple) or Gram-negative (red/pink) based on cell wall composition.

Mycolic Acid

A lipid (cord factor) present in the cell walls of Mycobacterium and Nocardia that confers high resistance to chemicals and dyes and is detected using the acid-fast stain.

Nucleoid

The region in a bacterial cell that contains condensed, single, circular, double-stranded DNA chromosome without a membrane bound enclosure.

Plasmids

Free, small, circular, double-stranded DNA molecules containing nonessential extra genes, frequently manipulated in genetic engineering.

Prokaryotic Ribosome

A $70\text{S}$ particle composed of $60\text{\%}$ ribosomal RNA and $40\text{\%}$ protein, made of a small $30\text{S}$ subunit and a large $50\text{S}$ subunit, that serves as the site of protein synthesis.

Inclusions and Granules

Intracellular storage bodies that store nutrients such as fat, phosphate, or glycogen deposited in dense crystals or particles.

Endospore

A dormant, highly resistant body produced within certain Gram-positive bacteria (such as Bacillus and Clostridium) capable of surviving extreme conditions.

Sporulation

The multi-step process of forming an endospore when a vegetative cell encounters harsh environmental conditions.

Germination

The process in which a dormant endospore revitalizes into a metabolically active vegetative bacterial cell.

Coccus

A spherical bacterial cell shape.

Bacillus

A cylindrical or rod-shaped bacterial cell.

Coccobacillus

A short, plump rod-shaped bacterial cell.

Vibrio

A gently curved, rod-shaped bacterial cell.

Spirillum

A rigid helical, comma, or twisted rod-shaped bacterial cell.

Spirochete

A flexible, spring-like spiral bacterial cell possessing periplasmic flagella.

Pleomorphism

The phenomenon where individual cells of a single species vary in cell shape and size.

Diplococci

An arrangement of cocci occurring in pairs resulting from cell division in one plane.

Streptococci

An arrangement of cocci in chains of variable lengths.

Staphylococci

An arrangement of cocci forming irregular, grape-like clusters resulting from division in several planes.

Tetrad

An arrangement of cocci consisting of a packet of four cells resulting from division in two perpendicular planes.

Sarcina

A cubical packet arrangement of $8\text{ to }64$ cocci cells.

Palisades

An arrangement of bacillus cells aligned side-by-side in a fence-like structure.

Strain (or Variety)

A culture derived from a single parent that differs in metabolic or structural traits from other cultures of the same species.

Type (Subspecies)

A subspecies category established by differences in antigenic makeup (serotype), phage susceptibility (phage type), or pathogenicity (pathotype).

Cyanobacteria

Photosynthetic Gram-negative bacteria possessing extensive thylakoids with photosynthetic chlorophyll pigments that release oxygen during photosynthesis.

Green and Purple Sulfur Bacteria

Photosynthetic anaerobic bacteria containing bacteriochlorophyll that metabolize sulfides without producing oxygen.

Obligate Intracellular Parasite

A pathogen (such as Rickettsias or Chlamydias) that requires a host cell to survive and replicate.

Domain Archaea

A domain of prokaryotes lacking peptidoglycan in cell walls, containing unique membrane lipids, and adapted to extreme environmental habitats.