MICROM 410: Fundamentals of General Microbiology - Lecture 1

Vocabulary flashcards covering the introduction to microbiology, course organization, historical classification of life, molecular phylogenetics using 16S rRNA, and the comparative characteristics of the Three Domains of Life.

Microbe

A living organism that is too small to be seen with the naked eye, encompassing prokaryotes (Bacteria and Archaea) and single-celled eukaryotes (algae, fungi, protozoa).

Prokaryote

An organism (from the Greek 'pro-', meaning before, and 'karyon', meaning kernel or nucleus) whose cells lack a membrane-bound nucleus and membrane-bound organelles.

Eukaryote

An organism (from the Greek 'eu-', meaning true, and 'karyon', meaning kernel or nucleus) characterized by cells containing a membrane-bound nucleus, membrane-bound organelles, and cytoskeletal elements such as microtubules and microfilaments.

Virus

An acellular entity that lacks many of the hallmarks of living organisms and is dependent on host cellular machinery to replicate.

Epulopiscium

An exceptionally large prokaryote that surpasses typical prokaryotic dimensions and can be larger than unicellular eukaryotes such as Paramecium.

Antonie van Leeuwenhoek

The Dutch pioneer of microscopy who manufactured handheld single-lens microscopes and was the first to observe and document microscopic organisms.

Leeuwenhoek Microscope

A handheld, single-lens magnifying device developed in the seventeenth century featuring a specimen pin and focusing screws used to observe the microbial world.

Ernst Haeckel

The German biologist who published General Morphology of Organisms in 1866, proposing a four-kingdom system consisting of Animals, Plants, Protists, and Monera.

Robert Whittaker

The American ecologist who in 1969 proposed a five-kingdom classification system by adding Fungi to Animals, Plants, Protists, and Monera.

16S rRNA Gene

The gene encoding the small subunit ribosomal RNA of prokaryotes (equivalent to 18S rRNA in eukaryotes), utilized as the universal molecular chronometer due to its presence across all cells, conserved function, resistance to horizontal gene transfer, and combination of conserved and variable domains.

Conserved Regions (16S rRNA)

Segments within the small subunit rRNA molecule that remain largely unchanged across deep evolutionary time, allowing researchers to align sequences and assess phylogenetic divergence between distantly related organisms.

Variable Regions (16S rRNA)

Rapidly evolving segments within the small subunit rRNA sequence used to determine sequence divergence between closely related genera and species.

Methanogens

A specialized group of anaerobic Archaea that generate methane; their unique 16S rRNA sequence divergence from both bacteria and eukaryotes catalyzed the recognition of the three domains of life.

Three Domains of Life

The phylogenetic model proposed by Carl Woese that classifies all cellular life on Earth into three primary evolutionary lineages: Bacteria, Archaea, and Eucarya (Eukarya).

Asgard Archaea

A candidate superphylum of Archaea (including Lokiarchaeota and Heimdallarchaeota) that encode multiple eukaryotic signature proteins, indicating that eukaryotes branched from within the archaeal domain.

Eukaryotic Signature Proteins (ESPs)

Proteins historically thought to be unique to eukaryotes—such as actin, tubulin, nuclear pore complex proteins, and membrane-trafficking machinery—whose homologous coding genes were subsequently identified in Asgard Archaea.

Ether-linked Isoprenoids

The distinctive membrane lipids characteristic of Archaea, which contrast with the ester-linked fatty acids comprising the cell membranes of Bacteria and Eukarya.

Formylmethionine (fMet)

The modified amino acid that initiates protein translation in Bacteria and in eukaryotic organelles of bacterial origin (mitochondria and chloroplasts), distinct from the unmodified methionine used by Archaea and the eukaryotic cytoplasm.

Archaea and Eukarya similarities / differences from Bacteria

Main Point: Transcription and Translation

Archaea and Eukarya

Introns are common

Eukaryotic homologs (for RNA polymerase and transcription factors)

Ribosome sensitivity = resistant

Transcription inhibitor = methonine

Bacteria

Introns are rare

Bacterial homologs (for RNA polymerase and transcription factors)

Ribosome sensitivity = sensitive

Transcription inhibitor = formylmethoine

Bacteria and Archaea similarities / differences from Eukaryotes

Genomic structure and metabolic diversity

DNA chromosome = circular

Gene organization = multigene operons

Metabolism = denitroficiation, respiration, fermentation