1. Classification of Microorganisms Part 1
Chapter 10
Classification of Microorganisms
Part 1

2. Terminology Taxonomy Systematics or phylogeny
The science of classifying organisms
Provides universal names for organisms
Provides a reference for identifying organisms
Systematics or phylogeny
The study of the evolutionary history of organisms

3. The Study of Phylogenetic Relationships
All Species Inventory ( )
To identify all species of life on Earth
Historic Background
1735 Plant and Animal Kingdoms
1857 Bacteria & fungi put in the Plant Kingdom
1866 Kingdom Protista proposed for bacteria, protozoa, algae, & fungi
1937 "Prokaryote" introduced for cells "without a nucleus"

4. The Study of Phylogenetic Relationships
1961 Prokaryote defined as cells in which nucleoplasm is not surrounded by a nuclear membrane
1959 Kingdom Fungi
1968 Kingdom Prokaryotae proposed
1978 Two types of prokaryotic cells found (sequence in rRNA)
1979 Three domain system proposed (Woese) above 5 kingdoms (based on the rRNA nucleotide sequence)

5. The Three-Domain System
Table 10.1

6. The Three-Domain System
Figure 10.1

7. The Three-Domain System
Table 10.2

8. Endosymbiotic Theory
Figure 10.2
Figure 10.3

9. A Phylogenetic Hierarchy
Implies that a group of organisms evolved from a common ancestor
Some of the information used to classify comes from fossils
Fossil evidence not available for most prokaryotes
Phylogeny for prokaryotes based on DNA hybridization and rRNA sequencing

10. Classification of Organisms
Rules for classifying and naming living organisms
several scientific entities are responsible for establishing rules
Scientific nomenclature (binomial nomenclature): genus and specific epithet (species)
Bacteria or prokaryotic scientific names taken from Latin (genus can be taken from Greek) or Latinized by adding suffix “-ales” & “-aceae”.
If reclassified, old name is often written in parentheses e.g. Enterococcus (Streptococcus) faecalis

11. References • Approved Lists of Bacterial Names
Based on published articles
• Approved Lists of Bacterial Names
Lists species of known prokaryotes
Based on rRNA sequencing
• Bergey’s Manual of Systematic Bacteriology
Provides phylogenetic information on bacteria and archaea
Morphology, differential staining, biochemical tests
• Bergey’s Manual of Determinative Bacteriology
Provides identification schemes for identifying bacteria and archaea

12. Scientific Nomenclature
Honors Oswaldo Cruz
Corkscrew-like (trypano-, borer; soma-body)
Trypanosoma cruzi
Spores spread in wind (nota)
Tuftlike (penicill-)
Penicillium notatum
Forms pus (pyo-)
Chains of cells (strepto-)
Streptococcus pyogenes
Stupor (typh-) in mice (muri-)
Honors Daniel Salmon
Salmonella typhimurium
Disease in fish
Honors Lois Pfiester
Pfiesteria piscicida
The disease
Source of Specific epithet
Honors Edwin Klebs
Kbebsiella pneumoniae
Source of Genus name
Scientific binomial

13. Taxonomic hierarchy
Figure 10.5

14. Species Definition
Eukaryotic species: a group of closely related organisms that breed (interbreed) among themselves but does not breed with individuals of another species
Prokaryotic species: a population of cells with similar characteristics
Clone: Population of cells derived from a single cell
Strain: Genetically different cells within a clone

15. Domain Eukarya
Animalia: Multicellular; no cell walls; chemoheterotrophic
Plantae: Multicellular; cellulose cell walls; usually photoautotrophic
Fungi: Chemoheterotrophic; unicellular or multicellular; cell walls of chitin; develop from spores or hyphal fragments
Protista: A catchall for eukaryotic organisms that do not fit other kingdoms

16. Prokaryotes
Figure 10.6

17. Classification of viruses
Viral species: population of viruses with similar characteristics that occupies a particular ecological niche
Viruses are not classified as part of the three-domain system
Ecological niche of a virus is its specific host cell
Viruses may be more closely related to their hosts than other viruses