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CLASSIFICATION of MICROORGANISMS Chapter 10 TAXONOMY • Taxis = orderly arrangement • Science of classifying living forms • Goal – allow for a natural classification system to depict relationships • Classification schemes – usually grouped by similar characteristics • EUKARYOTES – True nucleus, genetic material surrounded by a membrane • PROKARYOTES – No nuclear membrane surrounding the genetic material WHY and WHEN • • • • • Aristotle Animals and Plants 1859 – Darwin Theory of evolution Taxon (singular), taxa (plural) Phylogenetic – use common ancestor to show relatedness As microorganisms were being discovered problem as to classification WHERE TO PUT MICROORGANISMS? • 1857: Carl von Nageli plant kingdom • 1866: Ernst Haeckel new kingdom: PROTISTA – Include organisms lacking a nucleus and – Simple nucleated organisms (protozoa, fungi, algae) • 1937: Edward Chatton - prokaryotes – Term to denote organisms with no nucleus • 1968: R.G.E. Murray - Prokaryotae kingdom • 1969: Robert Whittaker - Five kingdom system – Prokaryotae (Monera); Protista; Fungi; Plantae; Animalia • 1978: Carl Woese – 3 domain system – Eukarya; Eubacteria; Archaebacteria The Three Domain System • Carl Woese: proposed that based on differences seen in the ribosomal RNA of cells, all living organisms can be classified into three domains. – Eukarya: protozoa, plants, animals, and fungi – Eubacteria: all pathogenic and non pathogenic true bacteria – Archaebacteria: Live in extreme env. Conditions and carry out unique biochemical rxs. • Methanogens: anaerobes, methane from CO2 • Halophiles: extreme salty conditions • Hyperthermophiles: very hot and acidic env. SCIENTIFIC NOMENTCLATURE • 18th C. – Caroleus Linnaeus developed 1st naming system using Latin words • Each organism is given a Genus name and a species name – – – – Binomial nomenclature Homo sapiens or Homo sapiens Klebsiella pneumoniae or Klebsiella pneumoniae H. sapiens or K. pneumoniae IF there is no question as to confusion with the Genus name • Species – Genus – Family – Order – Class – Phylum – Kingdom Domain Genus vs species • Genus: consists of species that differ from each other in some ways but have a common ancestor • Bacterial species: a group or population of cells with similar characteristics – Members are indistinguishable from each other but are different from members of other species – STRAIN: is a group of cells derived from a single cell • Often the name of the organism tells something about the shape, where it is found or what nutrients it uses – Escherichia coli – Staphylococcus aureus – Bacillus anthracis VIRUSES • Not classified in the 5 kingdom system because they are not CELLS • Obligate intracellular parasites – Can not replicate outside of host cell • Contain a core of nucleic acid – Either DNA or RNA but not both • Have a protein coat (capsid) that surrounds the genetic material • Utilize the host cell transcription and translation machinery to multiply and propagate • Classified by type of genetic material core, shape of capsid & presence or absence of an envelope BERGEY’S MANUAL of SYSTEMATIC BACTERIOLOGY • Not based on evolutionary relatedness BUT on identification scheme based on physical and chemical characteristics • Morphology (shape) • Differential staining (Gram, Acid-Fast) • Biochemical tests – Enzyme production (catalase, oxidase, coagulase & hemolysins – Oxygen requirements (aerobic, anaerobic, facultative anaerobes) – Carbohydrate utilization • Additional information regarding ecology, cultivation, taxonomy etc.