Narsing Rao, Manik

Traditionally, prokaryotes were classified based on phenotypic characteristics such as morphological, physiological, and biochemical characteristics. Later, the chemotaxonomy approach was introduced, which deals with the chemical characterization of various cell structural elements such as outer cell layers, cell membranes, and cytoplasm constituents. Traditional approaches produce data with low reproducibility and unacceptable marginal errors. In this regard, genotypic characterization was introduced, which involved comparing genetic material. Taxonomic classification today is based on a polyphasic approach that includes phenotypic, chemotaxonomic, and genotypic characteristics. The present chapter describes various phenotypic- and genotypic-based characteristics.