Chapter 1: Evolution of Microorganisms & Microbiology

Vocabulary flashcards covering key terms and concepts from the lecture notes on the evolution of microorganisms, microbial diversity, and foundational microbiology concepts.

3 Domain System

Carl Woese’s classification of life into Bacteria, Archaea, and Eukarya based on rRNA and genetic sequences.

Bacteria (Domain)

Prokaryotic domain with cell walls containing peptidoglycan; a major group of microbes.

Archaea (Domain)

Prokaryotic domain with distinct membrane and cell-wall chemistry; often extremophiles.

Eukarya (Domain)

Domain of organisms with eukaryotic cells (nucleus and organelles).

Cellular organisms

Microbes that are composed of cells (bacteria, archaea, and eukaryotes).

Acellular infectious agents

Infectious agents lacking cellular structure, including viruses, viroids, satellites, and prions.

Viruses

Smallest microbes that require a host cell to replicate; nucleic acid enclosed in a protein shell.

Viroids

Infectious RNA molecules that lack a protein coat.

Satellites

Nucleic acids enclosed in a protein shell that require coinfection with a virus to complete their life cycle.

Prions

Infectious proteins that cause neurodegenerative diseases.

Nucleoid

Region in bacterial cells where DNA is located, not enclosed by a membrane.

Capsule

Gel-like layer outside the bacterial cell wall that can protect against immune attack.

Cell wall

Structural layer outside the plasma membrane; in bacteria contains peptidoglycan.

Plasma membrane

Phospholipid bilayer surrounding the cytoplasm; controls movement of substances.

Pili (Fimbriae)

Hair-like appendages used for attachment and DNA transfer.

Flagellum

Tail-like structure used for bacterial motility.

Plasmid

Extra-chromosomal circular DNA carrying accessory genes.

LUCA

Last Universal Common Ancestor; the root of all modern life shared by Bacteria, Archaea, and Eukarya.

Endosymbiotic theory

Origin of mitochondria and chloroplasts from free-living bacteria that entered into a symbiotic relationship with early eukaryotes.

Mitochondria

Eukaryotic organelles of bacterial origin that produce ATP.

Chloroplasts

Photosynthetic organelles in plants/algae from endosymbiotic cyanobacteria.

RNA world

Hypothesis that early life used RNA as both genetic material and catalyst; ribozymes catalyze reactions.

Ribozyme

RNA molecules that catalyze chemical reactions, including peptide bond formation.

Stromatolites

Layered mineralized structures formed by ancient microbial mats, evidence of early life.

FeS hypothesis

Idea that early metabolism used iron-sulfur minerals as energy sources.

Cyanobacteria

Photosynthetic bacteria that contributed to oxygenation of Earth’s atmosphere around 2.7 billion years ago.

Koch’s postulates

Four criteria linking a microbe to a disease: presence in disease, isolation, reproduction of disease in a healthy host, re-isolation.

Pasteurization

Heating liquids to kill pathogens and reduce spoilage; developed by Louis Pasteur.

Immunology

Branch of biology studying the immune system; pioneers include Jenner (vaccination) and Behring/Kitasato (antitoxins).

Binomial nomenclature

System of naming species by Genus and species epithet.

Strain

Descendants of a single pure microbial culture; may be biovars, morphovars, serovars, or pathovars.

Horizontal gene transfer

Transfer of genetic material between organisms other than parent to offspring, common in Bacteria and Archaea.

Protozoa

Animal-like protists within Eukarya.

Algae

Photosynthetic eukaryotes within Eukarya.

Yeast

Unicellular fungi within Eukarya.

Molds and mushrooms

Multicellular fungi within Eukarya.

Spontaneous generation

Idea that life arises from nonliving matter; disproven by experiments (e.g., Pasteur).

Enrichment culture

Technique to promote growth of specific microbes by providing selective nutrients.

Nitrogen fixation

Microbial conversion of atmospheric N2 into ammonia usable by living organisms.