Classification and Naming of Microoganisms

Classification or Microorganisms

            Taxonomy--science of classification

                        systematic arrangement of organisms into groups-taxa

            Microbial systematics--classifying, naming, and identifying

Taxonomy--orderly arrangement of units into groups of

 larger groups of increasing inclusiveness

                        Nomenclature--naming of units characterized

                                    and delineated by classification

                        Identification—characterization (known to unknown),

                                    description, and comparison (literature descriptions)

            Objective:   group organisms so as to reflect similarities and differences

                        1750’s--Carolus LInnaeus--Systema Naturae

                                    Binomial nomenclature

                                    Kingdoms Animalia and Plantae

            Species Concept--basic unit of classification

                        Microbiological species concept--arbitrary / subjective


1)      distinguishable from other groups

2)      interbreading within the group (only)

assessments by researchers

            Taxonomic categories (taxa--pl.  or taxon--sing.)



“…for most groups of bacteria, genera and species are the only categories that can be recognized and defined with reasonable precision.”--Bergey’s Manual

                        species is most important group of classification


Naming Microorganisms  (Binomial nomenclature)

            Purpose:  provide a means of international reference

                        Latin or Latinized genus name and specific epithet

            Codes of nomenclature

                        International Code of Zoological Nomenclature--1901

                        International Code of Botanical Nomenclature--1906

                        International Code of Nomenclature of Bacteria--1947

                                    Int. Assoc. of Microbiological Societies

                                    Latest update 1975

                        Principles of nomenclature

1)      distinct organisms are designated as species

2)      latin / latinized binomial nomenclature

3)      naming congruent with international code

4)      law of priority

5)      designation of categories (classification)

6)      criteria used for formation and publication of new names


Developments in Taxonomy

            Numerical taxonomy--numerical values are assigned to the

overall similarities or proportion of characteristics common to organisms

            Taxa are established on degrees of similarity

            Advantages--objective and reproducible

            Genetic taxonomy--nucleotide / nucleocide compositions are

used to determine similarity between species

            Single strand recombination

Taxonomic Dynamic--“clumpers vs. splitters”

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