HIGH GENETIC AND PHYSIOLOGICAL DIVERSITY OF SULFATE-REDUCING BACTERIAISOLATED FROM AN OLIGOTROPHIC LAKE SEDIMENT

The community structure of sulfate-reducing bacteria in littoral and p rofundal sediments of the oligotrophic Lake Stechlin (Germany) was inv estigated. A collection of 32 strains was isolated from the highest po sitive dilutions of most-probable-number series, and their partial 16S rRNA gene sequences and genomic fingerprints based on ERIC (enterobac terial repetitive intergenic consensus)-PCR were analyzed. The strains fell into eight distinct phylogenetic lineages, and the majority (70% ) showed a close affiliation to the genus Desulfovibrio. Most of the r emaining strains (22%) were related to the gram-positive Sporomusa and Desulfotomaculum groups. A high redundancy of 16S rRNA gene sequences was found within several of the phylogenetic lineages. This low phylo genetic diversity was most pronounced for the subset of strains isolat ed from oxic sediment layers. ERIC-PCR revealed that most of the strai ns with identical 16S rRNA gene sequences were genetically different. Since strains with identical 16S rRNA gene sequences but different gen omic fingerprints also differed considerably with respect to their phy siological capabilities, the high diversity detected in the present wo rk is very likely of ecological relevance. Our results indicate that a high diversity of sulfate-reducing bacterial strains can be recovered from the natural environment using the established cultivation media.