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Unformatted text preview: ferent strains. 1 O157:H7 One difficulty is deciding how different two isolates must be before one
describes them as different species rather than as different strains. Taxonomy: Nomenclature Strain Three-Domain Classification Line lengths are based on genetic
distances, i.e., longer lines reflect
greater differences. Methods of Identification
Note existence of other methods of visualization beyond Gram stain... Note Phenotype- vs.
Genotype-based classification. Nomenclature: “Bacterial
names may originate from
any language, but they
must be given a Latin
suffix.” (i.e., they must be
Latinized). Strain O157:H7 Recall Binomial Nomenclature. Three-Domain Classification Note that majority of genetic diversity is among
single-celled organisms Phenotypic Characteristics Taxonomic Rank Note that not all groupings of
microorganisms have taxonomic meaning:
e.g., lactic acid bacteria, endosporeformers, or enteric pathogens. These are
examples of classifying “mistakes” due to
phenotypic similarity that results from
convergent evolution. Microscopy: Gram stain, acid-fast stain, cell
morphology, cell arrangements.
Colony morphology: size, color, border shape, etc.
Growth on Differential media: blood agar, MacConkey
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- Spring '11