Microbial Taxonomy

Bacteria account for a major proportion of Earth’s biological diversity. They play essential roles in quite diverse environments and there has been an increasing interest in bacterial biodiversity. Microbial taxonomy deals with the classification (the orderly arrangement of organisms into taxonomic groups on the basis of similarity), identification and nomenclature (naming of taxa) of microorganisms (Coenye et al., 2005; Gevers et al., 2005; Mora & Amann, 2001; Vandamme et al., 1996). The terms Taxonomy and Systematics have been often used synonymously but the taxonomy is a specific part of systematics. While Taxonomy is the theory and practice of classifying organisms (Mayr & Ashlock, 1991), Systematics refers to the study of diversity of

[(Lehmann & Neumann, 1896]. At the beginning of the 20th century various biochemical and physiological properties of bacterial cultures were determined for their characterization and identification Buchanan, 1955. On the basis of phenotypic properties, Bacteria were classified as unicellular plants-“Schizomycetes” and later primitive Planrts “Protophyta” plants in the first edition (1923) and seventh edition (1957) of Bergey’s Manual of Determinative Bacteriology respectively [3].

The distinction of prokaryotes and eukaryotes was introduced in the 1960s.( R.Y. Stanier, C.B. Van Niel, The concept of a bacterium, Arch. Mikrobiol. 42 (1962) 17–35.) . and Bacteria were recognized as members of the kingdom Procaryotae (bergieis 8th ed).

Between the 1960s and the 1980s, chemotaxonomy (Minnikin et al., 1975), numerical taxonomy and DNA–DNA hybridization techniques (Brenner et al., 1969; Johnson, 1991) were used to . Over the last 50 years, DDH has been the ‘gold standard’ for bacterial species demarcation as it provides a clear and objective numerical threshold for a species

The current classification of Bacteria and Archaea is based on an operational-based model, the so-called polyphasic approach, comprised of phenotypic, chemotaxonomic and genotypic data, as well as phylogenetic information. it is necessary to use various methods to identify and characterize bacteria species and to study and determine the diversity of this domain. A combination of many different methodologies has been directed toward analyzing phenotypic, genomic, and phylogenetic characteristics for taxonomic purposes; this combination is defined as a ‘polyphasic approach’ (Bernardet et al., 2005; Colwell, 1970; Dahllöf, 2002; Gevers et al., 2005; Rodríguez-Valera 2004; Vandamme et al.,