Phylogenie und Diversität grüner Schwefelbakterien

The phylogeny of green sulfur bacteria (GSB) was studied on the basis of nucleotide sequences. Primers were constructed that allowed sequence analysis of the fmoA gene and his deduced amino acid sequences (FMO). On 16S rDNA basis a primer specific for GSB was developed. The largely congruent phylogenetic relationship of 16S rDNA, fmoA and FMO sequences gives considerable support to the phylogeny of GSB. Five distinct groups of strains were recognized and supported by the comparison of GC contents and salt dependence of strains. The resulting phylogenetic grouping of the GSB does not correlate with their current taxonomic classification. The aim of the present studies were also the analysis of natural communities. The strategy involves procedures which were adapted from the methods well-tried with pure cultures. The results give considerable support that the diversity of salt dependent GSB in the investigated habitats is not substantially greater than it is represented by the pure cultures. Furthermore, the salt dependent species seem to be cosmopolitical.