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.