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Early Classification Systems
• Carolus Linnaeus (1750s)– Established a uniform naming system based on
shared characteristics– Two Kingdom System
1.Plant2.Animal
– Binomial nomenclature
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Early Classification Systems
• Ernst Haeckel—1860s– Too many characteristics not accounted for in
Linnaeus’ system– Three Kingdom System
1. Plant2. Animal3. Protista
Prokaryote – No nucleus (“pro” – before) Eukaryote – Nucleus (“eu” – true)
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Modern Classification Systems
• Robert Whittaker (1969)– Five-Kingdom System
1. Monera - bacteria2. Protista – unicellular algae & protozoa3. Fungi – molds, yeasts & mushrooms4. Plantae – plants, mosses & multicellular algae5. Animalia – worms to vertebrates
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Five-Kingdom System Breakout
KingdomPhylum
ClassOrderFamilyGenus Species
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Knowing Phil can often find good surf.
Modern Classifications Systems• Carl Woese (late 1970s) >> Classification based on rRNA, sensitivity to
antibiotics and lipid structure of the membrane
– Three-domain system1. Archea2. Eubacteria 3. Eukarya
– Domain grouping does not override the KPCOFGS taxonomic groupings
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Prokaryotes
Eukaryotes
The Three-Domain System
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Classification based on rRNA, sensitivity to antibiotics and lipid structure of the membrane
Fig 3.7
Wider Acceptance of Three-Domain System
• Craig Venter (1996)– Celera Genomics
• Sequenced the human genome
– Showed that a species of archeabacteria was very different from bacteria
10http://student.ccbcmd.edu/courses/bio141/lecguide/unit1/3domain/3domain.html
Classifying Prokaryotes-Bacterial Taxonomy
• Bergey’s Manual (1924)– Criteria for classification and identification
• Morphology and other physical characteristics• Growth in culture• Metabolism• Antigenicity• Genetics• Pathogenicity• Ecology
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Bacterial Taxonomy
• Morphology– Cell size– Cell shape and arrangement– Staining reactions
• Indicates chemical components of cell walls
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Bacterial Taxonomy
• Growth in culture– Temperature, gas, light, nutrient requirements– Living host?
Bacterial Taxonomy
• Metabolism– Fermentation of carbohydrates– Utilization of specific substrates
• Determines if specific enzymes are present
– Production of specific products or waste products
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Bacterial Taxonomy
• Antigenicity– Serological test determine the immune response
elicited by the microorganism
Bacterial Taxonomy
• Pathogenicity– Causes disease?– Host – plant or animal?
• Ecology– Habitat
• Thermophile• Halophile
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Bacterial Taxonomy
• Genetics – RNA or DNA– Check the G-C ratio – Plasmids
This becomes very important very quickly in the scientific world
Molecular Taxonomy
• Basis for the three-domain system of classification
• Based on the presence of ribosomes in all living organisms
• Will become more complex as techniques evolve
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Accepted Nomenclature
• Binomial system that identifies each organism by a universally-accepted scientific name
First word – GenusSecond word – Species
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Accepted Nomenclature
• Genus sometimes from– Latin root: Bacillus – “small rod”– Greek root: Clostrdium – “small spindle”– People: Escherichia – Theodore Escherich who
isolated the cells in 1895
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Accepted Nomenclature
• Species names– Albus - white– Aureus - gold– Lutea – yellow– Meningitidis – inflammation of the meningies
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Proper Written Form
• Genus is Capitalized and italicized– May be abbreviated
• Species is lower case and italicized
Ex. Bacillus subtilisB. subtilis
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Unknown Bacterium
Positive Negative
Positive Negative
Positive Negative
Positive Negative Positive Negative
Citrobacter Escherichia Citrobacter Enterobacterintermedius coli freudii aerogenes
Gram Stain
Lactose fermentation
Indole production
Use of citrate as sole carbon source Methyl red reaction
MicroFocus 3.4 pg 85 – Dichotomous Key