Introduction to Microbiology: Prokaryotes, Cell Structure, Taxonomy, and Growth

A set of vocabulary-style flashcards covering key concepts from the lecture notes on prokaryotes, cell structure, staining, taxonomy, metabolism, and growth.

Domain

One of the three domains of life: Bacteria, Archaea, and Eukarya.

Prokaryote

An organism without a true nucleus or membrane-bound organelles; includes Bacteria and Archaea.

Binomial nomenclature

Genus name is capitalized and species name is lowercase; full name is italicized (e.g., Escherichia coli).

Glycocalyx

A polysaccharide-rich coating outside the cell (capsule or slime layer) that aids in adhesion, protection, and biofilm formation.

Capsule

A tight, thick glycocalyx layer that helps protect bacteria from the immune system and dehydration.

Slime layer

A loose, unbounded glycocalyx that aids in adherence and protection from drying.

Fimbriae

Short, numerous surface appendages used mainly for attachment and biofilm formation.

Pili

Longer, fewer appendages used for attachment and, in some cases, DNA transfer (conjugation).

Flagellum

A long, helical filament used for bacterial motility; consists of the filament, hook, and basal body.

Monotrichous

Single flagellum located at one pole of the cell.

Amphitrichous

Flagella at both ends of the cell.

Lophotrichous

Two or more flagella at one end of the cell.

Peritrichous

Flagella distributed over the entire cell surface.

Axial filament

Periplasmic flagella found in spirochetes; enable corkscrew movement.

Pilus (Pili)

Conjugation pilus used to transfer DNA between bacteria; different from fimbriae.

Pellicle

Glycoprotein film on tooth enamel that binds salivary components and aids bacterial adherence.

Glycocalyx

Communally used term for the sugar-rich coating (capsule/slime) around some bacteria.

Gram stain

Differential staining method dividing bacteria into Gram-positive (purple) and Gram-negative (pink/red) based on cell wall structure.

Crystal violet

Primary dye in Gram staining; stains both Gram-positive and Gram-negative cells purple.

Mordant (iodine)

Chemical that locks the dye to the peptidoglycan layer by forming a dye–iodine complex.

Decolorization

Alcohol treatment that dehydrates and disrupts outer membranes; Gram-negative cells lose the dye, Gram-positive retain it.

Safranin

Counterstain used in Gram staining to color Gram-negative cells pink/red after decolorization.

Peptidoglycan

Polymer of NAM and NAG forming the bacterial cell wall; cross-linked by peptide bridges; thicker in Gram-positive bacteria.

Teichoic acids

Polymers in Gram-positive cell walls that help with cell wall maintenance and charge interactions.

Lipoteichoic acids

Teichoic acids anchored to the cell membrane in Gram-positive bacteria.

Lipopolysaccharide (LPS)

Component of the Gram-negative outer membrane; includes endotoxin and lipid A.

Periplasmic space

Space between the inner (cytoplasmic) membrane and outer membrane in Gram-negative bacteria.

Porins

Protein channels in the outer membrane of Gram-negative bacteria that allow diffusion of small molecules.

Mycobacterium

Bacteria with a waxy, lipid-rich outer membrane; typically requires acid-fast staining.

Mycoplasma

Bacteria lacking a cell wall; membrane contains sterols; Gram stain inconclusive.

Nucleoid

Region in the bacterial cell where the chromosome (usually circular) resides; no true nucleus.

Plasmid

Small, circular, extrachromosomal DNA that carries genes (e.g., antibiotic resistance) and can be transferred between cells.

Ribosome 70S

Bacterial ribosome composed of 50S and 30S subunits; targets differ from eukaryotic 80S ribosomes.

Inclusion bodies

Storage granules for nutrients (sulfur, phosphate, glycogen) or other substances.

Cytoskeleton

Internal protein scaffold that maintains cell shape and aids in intracellular transport; not present in all bacteria.

Endospore

Dormant, highly resistant cell form produced by some Gram-positive bacteria (e.g., Bacillus, Clostridium) under stress.

Sporulation

Process of endospore formation in response to nutritional stress; sporangium forms mature spore.

Spore vs vegetative cell

Endospore is the resistant dormant form; vegetative cell is the active, growing form.

Spore germination

Return from the endospore to a vegetative,-replicating cell when conditions are favorable.

Morphology: cocci

Spherical bacterial shape.

Morphology: bacilli

Rod-shaped bacteria.

Morphology: vibrio

Comma-shaped rod bacteria.

Morphology: spirillum

Rigid helical spiral-shaped bacteria.

Morphology: spirochete

Flexible, spring-like spiral bacteria with axial filament.

Pleomorphic

Organisms that do not have a single fixed shape, often due to lack of a cell wall.

Cocci arrangements

Diplococci (pairs); Streptococci (chains); Tetrads (groups of 4); Sarcinae (cubic); Staphylococci (irregular clusters); Palisades (stacked/hinge-like).

Staphylococcus aureus vs Staphylococcus epidermidis

Two species in the genus Staphylococcus; S. aureus is more virulent; S. epidermidis is less pathogenic.

Serotype

Antigenic variant within a species used to differentiate strains (e.g., Salmonella serotypes).

Strain

Genetically distinct isolate within a species (e.g., E. coli O157:H7).

Type

Subspecies variant with a distinct antigenic makeup; used to differentiate within a species.

Taxonomy sources

Classification methods: morphology, physiology/biochemistry, serology (antibodies), and genetic sequencing (e.g., rRNA).

Bergey’s Manual

Reference work (the Bacteria Bible) for systematic bacteriology; gold standard taxonomy guide.

Autotroph

Organism that fixes carbon dioxide to synthesize organic substances.

Heterotroph

Organism that relies on organic compounds from other organisms for carbon.

Chemolithotroph

Autotroph that obtains energy from oxidizing inorganic compounds.

Chemoorganotroph

Heterotroph that obtains energy from organic compounds.

Nitrogen fixation

Process by which some bacteria (e.g., Rhizobium) convert atmospheric N2 to NH4+ in a plant-smoothed environment.

Legume symbiosis

Rhizobium bacteria in legume root nodules fix nitrogen; leghemoglobin maintains anaerobic conditions for the enzyme nitrogenase.

Oxygen requirements

Categories: obligate aerobe, obligate anaerobe, facultative anaerobe, microaerophile, aerotolerant; determine where organisms grow best.

Thioglycolate broth

Gradient culture used to test oxygen tolerance by segregating organisms along the oxygen gradient.

pH classifications

Acidophile (low pH), neutrophile (neutral pH), alkaliphile (high pH).

Temperature classifications

Psychrophile, mesophile, thermophile, hyperthermophile; describe optimal growth temperatures.

Growth phases

Lag, exponential (log), stationary, and death phases; describe population changes over time.

Binary fission

Asexual bacterial reproduction where a parent cell divides into two genetically identical daughter cells.

FtsZ ring

Cytoskeletal ring that constricts to divide the cell during binary fission.