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Taxonomy
Classification of living organisms
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Importance of Taxonomy
- Provides common scientific language
- Allows grouping of unknown organisms
- Based on comparisons, similarities (DNA, rRNA, metabolism...)
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Binomial nomenclature
Names all living organisms with a Genus species designation (italicized or underlined)
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Entamoeba histolytica
intestinal
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Escherichia coli
Named after Theodor Escherich in 1888; found in the colon
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Haemophilus ducreyi
- Hemo - blood
- phil - love
- Agusto Ducrey 1889
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Nesisseria gonorrhoeae
Named after Albert L neisser in 1879; causes gonorrhea
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Saccharomyces cerevisiae
- Saccharo-sugar
- myco-mold
- cerevisia-beer or ale
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Staphulococcus aureus
- Stapho-cluster
- kokkus-berry
- Aureus-golden
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Shugella etousae
Named after Kiyoshi Shiga in 1898; European Theater of Operations of the US Army (final e gives proper Latin ending)
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Strain
Species subdivision
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Bergery's Manual of Bacteriology
Classifies all known bacteria using criteria such as morphology, cell wall composition, O2 requirements, biochemical testing of enzymes/metabolism
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Sugar fermentation
Organism is inoculated into a medium containing a specific sugar; growth and end products of fermentation, including gases, are noted.
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Gelatin liquefaction
Organism us inoculated into a solid medium contain gelatin; liquefaction at room temp or inability to re-solidify at refrigerator temp indicates the presence of proteolytic (protein digesting) enzymes
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Catalase
Hydrogen peroxide is poured over heavy growth of an organism on an agar slant; release of O2 gas bubbles indicated the presence of catalase, which oxidizes H2O2 to H2o and O2
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Oxidase
Two or three drops of an oxidase test reagent are added to an organism growing on an agar plate; a color change of the test reagent to blue, purple or black indicated the presence of cytochrome oxidase
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Citrate utilization
Organism is inoculated into citrate agar medium in which citrate is the sole carbon source; an indicator is the medium changes color if citrate is metabolized; use of citrate indicates the presence of the permease complex that transports citrate into the cell
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Two ways to classify life
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5-Kingdom
- Traditional
- Plantae Pungi Animalia
- Protista
- Monera
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2 main prokaryotic groups (domains)
- Eubacteria
- Archaeobacteria
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Eubacteria
- Most common bacteria
- Eg- gm(+), gm(-), all pathogens
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Archaeobacteria
- Differ: Cell wall (no peptidoglycan), antibiotic sensitivity, membranes
- Live in extreme environments (thermophiles and halophiles)
- Unusual metabolism (methanogens)
- Most ancient forms of life
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