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BIO 411 – Medical Microbiology. Chapter 2 Bacterial Classification. Phenotypic Classification. Microscopic morphology Gram stain reaction Shape and arrangement Macroscopic morphology Blood hemolysis Colony shape and size Pigmentation Odor. Phenotypic Classification.
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BIO 411 – Medical Microbiology Chapter 2 Bacterial Classification
Phenotypic Classification • Microscopic morphology • Gram stain reaction • Shape and arrangement • Macroscopic morphology • Blood hemolysis • Colony shape and size • Pigmentation • Odor
Phenotypic Classification • Streptococcus pyogenes example: • Gram + • Forms long chains of cocci • Shows complete blood hemolysis • Small, white colonies • But this usually isn’t enough info. to ID the organism • Additional info. must be obtained
Phenotypic Classification • Biochemical Tests • Carbohydrate fermentation • Carbon source utilization • Presence of specific enzymes (proteases, nucleases, lipases, etc.) • This usually gives enough info. to ID most human pathogens • Some species can even be broken into sup-categories using biochemical tests. • This technique is called biotyping
Phenotypic Classification • Many bacteria possess antigens that are unique and can be used for ID • This technique is called serotyping • E. coli O157 • S. pyogenes
Genotypic Classification • Genotypic Classification Methods • G-C ratio • DNA hybridization (with species-specific probes) • Sequence analysis • PCR
Classification Schemes • Boxes 2-4 through 2-8