Functional gene studies of pure cultures are the basis of systematic studies of environmental communities of phototrophic bacteria and their species specific analyses

Abstract

From the establishment of proper cultivation conditions of phototrophic sulfur bacteria 50 years ago up to today significant improvements have been made to systematically treat the phototrophic green and purple sulfur bacteria and identify them in environmental communities. Important steps for these improvements were first of all the description of a large number of pure cultures representing a proper fraction of environmental diversity, their correct taxonomic treatment and the clear definition of the taxa. Further important steps were the establishment of a phylogenetics-based taxonomy supported by 16S rRNA gene sequences and the demonstration of congruence between phylogenies based on 16S rRNA genes and functional genes. The formation of a large database of fmoA genes of green sulfur bacteria and of pufLM genes of purple sulfur bacteria and their obvious phylogenetic congruence with the 16S rRNA gene enabled detailed studies of environmental communities of these bacteria and the recognition of species and genera in natural habitats. The comprehensive studies of selected habitats yielded promising results and demonstrated the potential of this approach for the systematic characterization of environmental communities