Classification and Nomenclature

Chap 3

1

Classification Systems: Taxonomy

2

Early Classification Systems

• Carolus Linnaeus (1750s)– Established a uniform naming system based on

shared characteristics– Two Kingdom System

1.Plant2.Animal

– Binomial nomenclature

3

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)

4

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

5

The Five-Kingdom System

6Fig 3.6Still based primarily on external characteristics

Five-Kingdom System Breakout

KingdomPhylum

ClassOrderFamilyGenus Species

7

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

8

Prokaryotes

Eukaryotes

The Three-Domain System

9

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

11

Bacterial Taxonomy

• Morphology– Cell size– Cell shape and arrangement– Staining reactions

• Indicates chemical components of cell walls

12

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

14

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

18

Nomenclature

19http://student.ccbcmd.edu/courses/bio141/lecguide/unit1/3domain/3domain.html

Accepted Nomenclature

• Binomial system that identifies each organism by a universally-accepted scientific name

First word – GenusSecond word – Species

20

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

21

Accepted Nomenclature

• Species names– Albus - white– Aureus - gold– Lutea – yellow– Meningitidis – inflammation of the meningies

22

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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24

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