RESUMO
Communities of green sulfur bacteria were studied in selected marine and saline habitats on the basis of gene sequences of 16S rRNA and the Fenna- Matthews-Olson (FMO) protein. The availability of group-specific primers for both 16S rDNA and the fmoA gene, which is unique to green sulfur bacteria, has, for the first time, made it possible to analyze environmental communities of these bacteria by culture-independent methods using two independent genetic markers. Sequence results obtained with fmoA genes and with 16S rDNA were largely congruent to each other. All of the 16S rDNA and fmoA sequences from habitats of the Baltic Sea, the Mediterranean Sea, Sippewissett Salt Marsh (Massachusetts, USA), and Bad Water (Death Valley, California, USA) were found within salt-dependent phylogenetic lines of green sulfur bacteria established by pure culture studies. This strongly supports the existence of phylogenetic lineages of green sulfur bacteria specifically adapted to marine and saline environments and the exclusive occurrence of these bacteria in marine and saline habitats. The great majority of clone sequences belonged to different clusters of the Prosthecochloris genus and probably represent different species. Evidence for the occurrence of two new species of Prosthecochloris was also obtained. Different habitats were dominated by representatives from the Prosthecochloris group and different clusters or species of this genus were found either exclusively or as the clearly dominant green sulfur bacterium at different habitats.
Assuntos
Proteínas de Bactérias/genética , Chlorobi/crescimento & desenvolvimento , Chlorobi/genética , Ecossistema , Complexos de Proteínas Captadores de Luz/genética , RNA Ribossômico 16S/genética , Variação Genética , Sedimentos Geológicos/microbiologia , Filogenia , Microbiologia da ÁguaRESUMO
The phylogeny of green sulfur bacteria was studied on the basis of gene sequences of the 16S rRNA and of the Fenna-Matthews-Olson (FMO) protein. Representative and type strains (31 strains total) of most of the known species were analyzed. On the basis of fmoA gene sequences from Chlorobium tepidum ATCC 49652(T) and Chlorobium limicola DSM 249(T) available from the EMBL database, primers were constructed that allowed sequence analysis of a major part of the fmoAgene. The largely congruent phylogenetic relationship of sequences of the fmoA gene and of 16S rDNA gives considerable support to the phylogeny of green sulfur bacteria previously suggested on the basis of 16S rDNA sequences. Distinct groups of strains were recognized on the basis of 16S rDNA and FMO sequences and supported by characteristic signature amino acids of FMO. Marine strains formed clusters separate from freshwater strains. The resulting phylogenetic grouping and relationship of the green sulfur bacteria do not correlate with their current taxonomic classification.