Ch. 10: Classification of Microorganisms

Lu

Taxonomy

the science of classifying organisms into taxa (categories)

Carolus Linnaeus

(1735) developed binomial nomenclature that consistently and accurately names organisms

• each organism has two names:

  • genus (generalized)

  • specific epithet (specific species)

Prokaryotes

• unicellular

• lack a membrane-bound nucleus and organelles

• two distinct domains: bacteria & archaea

Eukaryotes

• possess membrane-bound nucleus that have genetic material AND organelles

• under the eukarya domain

Carl Woese

(1990) developed the three-domain system based on the similarity in sequences of nucleotides in rRNA gene (highly conserved)

Taxonomic Hierarchy

• Domain (Dear)

• Kingdom (King)

• Phylum (Philip)

• Class (Came)

• Order (Over)

• Family (For)

• Genus (Good)

• Species (Soup)

Prokaryotic species

a population of cells with a high degree of genomic similarity

• culture: bacteria grown in a lab

• clone: population derived from a single parent

• strain: genetically different cells within a clone

Robert Whittaker

(1969) formed the five-kingdom system based on observable characteristics

• prokaryotes = monera

• eukaryotes = protistia, fungi, plantae, animalia

Viral Species

population of viruses with similar characteristics that can be distinguished from other species by multiple criteria

• not part of any domain

• not made of cells

• needs a host