Prokaryote Taxonomy & DiversityClassification, Nomenclature & IdentificationPhenetic ClassificationMolecular Phylogeny Approach

Classification (hierarchical grouping of taxa, based on characteristics)

Nomenclature (formal naming of taxa)

Identification (define characteristics that match a particular taxa).

Phylogeny (study of evolutionary relationships)

Bergeys Manual of Systematic Bacteriology1st ed. (1984); mostly phenetic classification; 4 volumes 2nd ed. (in prep); mostly phylogenetic classification; 5 volumes

Species Concept for ProkaryotesDefined differently than Eukarya (no sexual reproduction) = genetically unique population with many stable characters distinctly different from other groups.

Strains are variations within a species; characterized by minor differences in biochemical/ physiological properties (biovars), antigenic distinctions (serovars), shape (morphovars), or viral susceptibility (phage-typing).

Phenetic Characters:3) Morphological Characters4) Physiological and Metabolic CharactersVery useful in identification!1) Ecological Characters2) Genetic Characters

Phenetic IdentificationUse of dichotomous keys for bacteria

Phenetic IdentificationUse of multi-test kits and their databases.The combination of positive results from an unknown is entered into a database of results form known bacteria. A computer model predicts the most probable match and level of certainty. Intended use is for clinical isolates.

Molecular Characters Fatty acid profiles (FAME analysis)Proteins Electrophoretic Mobility Immuno-Reactivity A.A. Sequence DataNucleic Acids Nucleotide composition (G+C content Tm) Degree of Hybridization (>70% species) Nucleotide Sequence Data

Phylogenetic Classification Molecular ChronometersPhylogeny 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.Rate of sequence change commensurate with evolutionary distance measured.

Small subunit rRNA of the three domains of life.Bacteria 16SrRNAArchaea 16SrRNAEucarya 18SrRNA

Microbial Diversity Assignment