A Phylogenetically Oriented Taxonomy of Anoxygenic Phototrophic Bacteria

Abstract

Historically, the taxonomy of phototrophic bacteria, like all other bacteria, has been based on easily recognizable phenotypic properties (Pfennig and Trüper, 1974). Although the ability to perform photosynthesis together with the possession of a photosynthetic apparatus and photosynthetic pigments has since Molisch (1907) been considered as primary criterion to distinguish phototrophic from non-phototrophic bacteria and it was implicated that phototrophic bacteria might constitute a separate phylogenetic line, it always had been clearly recognized that the taxonomic system had a practical background and did not constitute a phylogenetic system. Indeed, phylogenetic information became available only with the establishment of sequencing techniques for proteins and nucleic acids on the basis of sequences of cytochromes c (Ambler et al., 1979) and oligonucleotides obtained from 16S rRNA digestion with specific endonucleases (Gibson et al., 1979; Fowler et al., 1984; Stackebrandt et al., 1984), later by complete sequences of the 16S rRNA gene.