Taxonomy of Cellular Life

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Taxonomy of Cellular Life
Know domains (Tables 10.1 10.2)
Taxonomy classification (hierarchical grouping
based on characteristics) nomenclature (naming)
identification (define characteristics that match
taxa).
Phylogeny study of evolutionary relationships.
Comparison of rRNA base sequences is most common.
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Classification Taxa Hierarchy

• Prokaryote (e.g. E. coli)
• Domain Bacteria
• (no kingdom)
• Phylum Proteobacteria
• Class ?-proteobacteria
• Order Enterobacteriales
• Family Enterobacteriaceae
• Genus Escherichia
• Species coli

• Eukaryote (e.g. Humans)
• Domain Eukarya
• Kingdom Animalia
• Phylum Chordata
• Class Mammalia
• Order Primata
• Family Hominidae
• Group Homo
• Species sapiens

Binomial nomenclature Genus species (italic or
underlined) Just like varieties of apples, or
races of people, there are strains of a
prokaryote species (e.g. the harmless Escherichia
coli K12 versus the deadly pathogenic E. coli
O157H7). Why so?
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Phenetic Characters
3) Physiological and Metabolic Characters
Very useful in identification! 1) Ecological
Characters
2) Morphological Characters
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Phenetic IdentificationUse of dichotomous keys
for bacteria
Manually run individual analyses of phenotype
(staining, metabolic tests, etc) needed in the
key.
Sequentially progress through the key until you
reach an end point. The example here stops at
the genus level.
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Phenetic IdentificationUse of multi-test kits
and their databases.
This is the EnteroTube II test for members of the
Enterobacteriaceae Different media are used to
determine specific metabolic capabilities (e.g.
lactose fermentation or citrate use) Numerical
code is interpreted from an established
database. Often there are different kits for
different groups mostly restricted to medically
important bacteria.
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Molecular Characters

• Fatty acid profiles (FAME analysis)
• Proteins
• Electrophoretic Mobility
• Immuno-Reactivity (Serotyping)
• A.A. Sequence Data
• Nucleic Acids
• Nucleotide composition (GC content Tm)
• Degree of Hybridization (gt70 species)
• Nucleotide Sequence Data

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Small subunit rRNA of the three domains of life.
Bacteria 16SrRNA
Archaea 16SrRNA
Eucarya 18SrRNA
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Phylogenetic Classification Molecular
Chronometers

• Phylogeny refers to grouping based on
  evolutionary relatedness regardless of phenetic
  characters.
• Phylogeny is inferred from changes in protein or
  rRNA sequence over time.
• Attributes of an Ideal Molecular Chronometer
  Universally distributed.
• Functionally homologous.
• Ease of analysis (get enough information
  quickly).
• Sequence changes reflects a measurement of
  evolutionary distance between organisms.
• Similarity between organisms sequences are used
  to create a graphical representation, called a
  cladogram or phylogenetic tree. (See example Fig
  10.17.)

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10
Microbial Diversity Assignment
Complete by Exam 3 on April 9th, 2003, for
participation marks (2 final grade). You may
work in groups of three or fewer. (1 Extra
Credit if completed by Friday, March 21st, 2003.)
Know these 13 prokaryote groups, including five
classes of Proteobacteria, and selected fungi,
algae, protozoa and helminths.
Total Extra Credit Ops 4 STSS 2 Ch 7 1
M.D.A. (Ch 11 12) 7 (about two grade
intervals).