Microbiology Fundamentals – Bacteria, Archaea, Viruses & Identification Methods

A set of vocabulary flashcards covering microbial shapes, taxonomy, extremophiles, virus classification, and laboratory identification methods highlighted in the lecture transcript.

Introns (in bacteria)

Non-coding RNA segments absent in bacterial genes, simplifying their genetic regulation compared with eukaryotes.

Binary fission

Asexual reproduction in which a bacterial cell replicates its genome and splits into two identical daughter cells.

Peptidoglycan

Rigid, cross-linked polymer that forms the bacterial cell wall and provides structural support.

Bacillus (plural: bacilli)

Rod-shaped bacterial cell morphology.

Coccus (plural: cocci)

Spherical bacterial cell morphology.

Spirochete

Spiral-shaped bacterium lacking visible flagella; classified primarily by its shape.

Flagellum

Long, whip-like appendage some bacteria use for self-propelled movement.

Proteobacteria

Large bacterial phylum classified mainly by specific peptidoglycan arrangements in the cell wall.

Actinobacteria

Bacterial phylum often high in G+C DNA content and distinct from Proteobacteria.

Vulgar nomenclature

Commonly used, entrenched names (e.g., E. coli) that persist despite taxonomic revisions.

Archaea

Prokaryotes distinct from true bacteria; lack peptidoglycan, possess unique membranes, and include many extremophiles.

Extremophile

Microorganism, often archaeal, that thrives in physically or chemically extreme environments.

Hyperthermophile

Extremophile that grows optimally at or above boiling temperatures.

Acidophile

Organism thriving in highly acidic environments (pH ~3–4).

Sulfur bacteria

Microbes that use elemental sulfur as a primary energy source, often producing yellow or orange deposits.

Baltimore classification

Virus taxonomy system organizing viruses by nucleic-acid type (DNA or RNA) and strandedness (single vs. double).

Phenotyping (microbial)

Identifying an organism through observable traits such as shape, staining, metabolism, and culture behavior.

Serotyping (serological testing)

Rapid identification based on specific antigen–antibody reactions; e.g., COVID-19 rapid test.

Genotyping

Highly accurate identification through analysis and sequencing of an organism’s DNA.

Culture characteristics

Macroscopic traits of microbial growth on agar—colony color, shape, texture, and pigment production.

Blood agar

Agar medium enriched with 5 % sheep blood used to assess hemolytic properties of bacteria.

Beta hemolysis

Complete lysis of red blood cells on blood agar, leaving a clear zone around colonies.

Alpha hemolysis

Partial hemolysis producing a greenish halo on blood agar.

Gamma hemolysis

No red-cell lysis observed on blood agar.

Catalase

Enzyme that decomposes hydrogen peroxide; often tested to gauge bacterial defensive capability against oxidative bursts.

Oxidase test

Assay detecting cytochrome c oxidase to differentiate aerobic from facultative anaerobic bacteria.

Lactose fermentation

Metabolic ability to break down lactose sugar; useful for distinguishing enteric bacteria.

Pseudomonas aeruginosa

Gram-negative rod notable for producing a characteristic green pigment on culture media.