Download CLASSIFICATION of MICROORGANISMS

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.