Classification and microbial groups

Taxonomy

The classification, description, identification and naming of living organisms.

Binomial nomenclature

Two-word naming system identifying organisms by genus and species.

Acellular

Not composed of cells.

Virus

Acellular microbe made of proteins and genetic material, either DNA or RNA, never both.

Viroid

Virus-like agent containing only a short strand of circular RNA that can self-replicate.

Prion

An infectious protein.

Prokaryote

Microorganism with no membrane-bound nucleus or organelles.

Eubacteria

Single-celled prokaryotic microorganism; "true" bacteria.

Archaea

Unicellular prokaryotic organism without peptidoglycan in the cell wall; none are known human pathogens.

Eukaryote

Microorganisms that have a membrane-bound nucleus and organelles.

Algae

Unicellular or multicellular photosynthetic eukaryote with cell walls made of cellulose.

Fungi

Unicellular or multicellular eukaryote with cell walls made of chitin; not photosynthetic.

Protozoa

Eukaryotic single-celled organisms; a very diverse group, usually categorized by mode of motility.

Helminth

Multicellular, eukaryotic parasitic worm visible to the naked eye, but with microscopic eggs and larvae.

Three domains of life

Bacteria, Archaea, and Eukarya; a system proposed based on ribosomal RNA (rRNA) sequence comparisons.

Carl Woese

Scientist who proposed the three-domain system of life based on ribosomal RNA (rRNA) sequences.

Kingdoms in Domain Eukarya

Protista (algae, protozoa), Fungi, Plantae, and Animalia (includes helminths).