Microbial Classification and Identification

Vocabulary flashcards covering major terms related to microbial classification, taxonomy, and laboratory identification methods presented in the lecture notes.

Three-Domain System

Classification introduced by Carl Woese (1978) that divides all life into Bacteria, Archaea, and Eukarya based on rRNA sequences.

Six-Kingdom System

Modern kingdom-level classification separating organisms into Bacteria, Archaea, Protista, Plantae, Fungi, and Animalia.

Endosymbiotic Theory

Idea that eukaryotic organelles such as mitochondria and chloroplasts originated from bacteria living inside ancestral prokaryotic cells.

Horizontal Gene Transfer

Exchange of genes between organisms other than by inheritance from parent to offspring; common among early microbes.

Conserved DNA

Genetic sequences that remain largely unchanged through evolution because they perform essential cellular functions.

Protist

Diverse group of mostly unicellular eukaryotes that are not classified as plants, animals, or fungi.

Prokaryote

Microorganism whose cell lacks a true nucleus and membrane-bound organelles; includes Bacteria and Archaea.

Eukaryote

Organism whose cells possess a nucleus and membrane-bound organelles.

Peptidoglycan

Mesh-like polymer forming most bacterial cell walls, composed of sugars and amino acids.

Ether Linkage

Bond connecting branched lipid chains to glycerol in archaeal cell membranes.

Ester Linkage

Bond connecting straight fatty acid chains to glycerol in bacterial and eukaryotic membranes.

Methionine

First amino acid inserted during protein synthesis in archaea and eukaryotes.

Formylmethionine

Modified methionine that initiates protein synthesis in bacteria (and mitochondria).

70S Ribosome

Smaller ribosome found in prokaryotes, mitochondria, and chloroplasts; composed of 50S and 30S subunits.

80S Ribosome

Larger cytoplasmic ribosome of eukaryotic cells; composed of 60S and 40S subunits.

Binomial Nomenclature

Two-part scientific naming system using genus and species epithet, e.g., Escherichia coli.

Taxonomic Hierarchy

Ordered classification levels: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Bergey’s Manual of Determinative Bacteriology

Reference providing systematic schemes for identifying bacteria and archaea.

Approved Lists of Bacterial Names

Official compilation of validly published bacterial species names used for nomenclature.

Pure Culture

Laboratory culture containing a single microbial species or strain.

Gram Stain

Differential staining procedure separating bacteria into Gram-positive and Gram-negative groups.

Biochemical Test

Laboratory assay detecting metabolic or enzymatic activities to aid microbial identification.

Durham Tube

Inverted tube placed in broth to trap gas produced during fermentation tests.

Rapid Identification Method

System (e.g., API strip) that performs multiple biochemical tests simultaneously for quick microbial ID.

Serology

Study of antigen-antibody reactions in serum used for diagnosis or organism identification.

RT-PCR (Reverse Transcription PCR)

Technique converting RNA to cDNA then amplifying it to detect RNA viruses such as SARS-CoV-2.

Nucleic Acid Amplification Test (NAAT)

Diagnostic method amplifying specific DNA/RNA sequences (e.g., PCR) to detect hard-to-culture microbes.

VNTR (Variable Number Tandem Repeat)

Short repeated DNA sequence whose repeat number varies between individuals; basis of DNA fingerprinting.

Metagenomics

Analysis of genetic material recovered directly from environmental samples, allowing study of uncultured microbes.

Endosymbiotic Organelle

Organelle such as a mitochondrion or chloroplast that originated from an ancestral endosymbiotic bacterium.