Phylogenetic, Evolutionary, and Taxonomic Aspects of Phototrophic Eubacteria

Abstract

The first microbiologist to investigate the taxonomy of phototrophic bacteria comprehensively was Winogradsky (1888) who used the term “sulfur bacteria” to combine the sulfur phototrophic bacteria and sulfur chemosynthetic bacteria in one systematic unit. This was later elevated by Migula (1900) to an order Thiobacteria, comprising the f ami lies Rhodobacteriaceae and Beggiatoaceae. Molisch (1907) combined the purple sulfur bacteria (Thiorhodaceae) and the purple nonsulfur bacteria (Athiorhodaceae) into an order Rhodobacteria, a move which was later criticised by van Niel (1946) who suggested it had as little justification as grouping the colorless and purple sulfur bacteria. It was Orta-Jensen (1909) who for the first time claimed a phylogenetic validity for the ranks he proposed. In his scheme the order Cephalotrichinae embraced the phototrophic bacteria in a family Rhodobacteriaceae. The most widely accepted classification scheme and the one that was later adopted for “Sergey’s Manual of Determinative Bacteriology” was established by Buchanan from 1916 onwards. Here the order Thiobacteriales was described for several families of colorless, purple sulfur and purple nonsulfur bacteria. ThiobacilLus, on the other hand, was not included in Thiobacteriales but was classified with the Eubacteriales. In his perceptive paper “The classification and natural relationships of bacteria” Niel (1946) summarized the events leading to the overclassification of these groups of bacteria and discussed the problems concerning the obvious phylogenetic relationship of the purple bacteria to many colorless sulfur bacteria.