Biology 144 – Microbial Diversity: Lecture 1 Vocabulary

Vocabulary flashcards covering key terms from Biology 144 Lecture 1 on microbial diversity, microscopy, classification, and the three domains of life.

Microbiology

The study of organisms in the micrometre size range, including bacteria, archaea, fungi, yeasts, viruses and protozoa.

Light Microscopy

A group of microscope techniques (brightfield, darkfield, phase-contrast, fluorescent, confocal laser) that use visible light and glass lenses to view specimens.

Electron Microscopy (EM)

Microscopy that uses electron beams instead of light, achieving ~1 000× higher resolution than light microscopes.

Transmission Electron Microscopy (TEM)

EM method in which electrons pass through an ultra-thin specimen to reveal internal cell structures.

Scanning Electron Microscopy (SEM)

EM method in which electrons scan a specimen’s surface, revealing detailed 3-D topography.

Magnification (Microscopy)

The product of the ocular lens (usually 10×) and the objective lens (e.g., 10×, 40×, 100×) that enlarges the image of a specimen.

Resolution (Microscopy)

The ability to distinguish two points as separate; much higher in EM than in light microscopy.

Prokaryote

Collective term for Bacteria and Archaea; cells lack a true nucleus and membrane-bound organelles.

Eukaryote

Domain of life whose cells have a true nucleus, membrane-bound organelles, and usually introns in DNA.

Domain Bacteria

True bacteria; small unicellular prokaryotes with peptidoglycan cell walls, reproducing by binary fission.

Domain Archaea

Prokaryotes adapted to extreme environments; lack peptidoglycan, possess unique membrane lipids and eukaryote-like genetic machinery.

Domain Eukarya

Includes algae, fungi, protists, plants and animals; cells are often multicellular, compartmentalised and reproduce sexually.

Peptidoglycan

A complex polymer in bacterial cell walls that provides rigidity; absent in Archaea and Eukarya.

Gram-positive Bacteria

Bacteria with thick peptidoglycan layers that retain crystal violet stain and appear purple under a microscope.

Gram-negative Bacteria

Bacteria with thin peptidoglycan and an outer membrane; do not retain crystal violet, appearing pink/red after counterstain.

Binary Fission

Asexual reproduction in prokaryotes where one cell divides into two genetically identical daughter cells.

Horizontal Gene Transfer

Movement of genetic material between organisms other than by descent, contributing to microbial diversity.

Nitrogen Fixation

Reduction of atmospheric N₂ to ammonia (NH₃) by certain prokaryotes, replenishing bioavailable nitrogen in ecosystems.

Cyanobacteria

Photosynthetic bacteria that produced Earth’s early oxygen and continue to fix carbon and nitrogen.

Extremophile

An organism, often an archaeon, that thrives in extreme conditions of temperature, pH, salinity or pressure.

Carl Woese

Microbiologist who proposed the three-domain system (Bacteria, Archaea, Eukarya) using 16S/18S rRNA sequencing.

16S rRNA Gene

Conserved component of prokaryotic small ribosomal subunit used for phylogenetic classification and identification.

Taxonomic Hierarchy

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

Binomial Nomenclature

Two-part Latin naming system for species, e.g., Escherichia coli, introduced by Carolus Linnaeus.

Species (Microbiology)

The basic taxon; a collection of microbial strains sharing many stable properties and differing significantly from other groups.

Strain (Type Strain)

Descendants of a single microbial colony; the reference strain for a species designation.

Phenotypic Classification

Grouping organisms by observable traits such as morphology, metabolism, and staining characteristics.

Genotypic Classification

Grouping organisms based on DNA similarity, commonly using conserved genes like rRNA sequences.

Endosymbiosis

Theory that mitochondria and chloroplasts originated from engulfed prokaryotes within early eukaryotic cells.

Metabolites (Microbial)

Diverse compounds produced by microbes, utilised in medicine, industry and environmental applications.