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Defined 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 Characters
4) Physiological and Metabolic Characters
Very useful in identification!
1) Ecological Characters
2) 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 Data
• Nucleic Acids– Nucleotide composition (G+C content ≈ Tm)– Degree of Hybridization (>70% ≈ species)– Nucleotide Sequence Data
• 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.– Rate of sequence change commensurate with