USE OF 16S RIBOSOMAL-RNA-TARGETED OLIGONUCLEOTIDE PROBES TO INVESTIGATE THE OCCURRENCE AND SELECTION OF SULFATE-REDUCING BACTERIA IN RESPONSE TO NUTRIENT ADDITION TO SEDIMENT SLURRY MICROCOSMS FROM A JAPANESE ESTUARY

The structures of prokaryotic communities are difficult to elucidate b ecause of the apparent inability to culture most of the indigenous mic roorganisms. Here we report the use of 16S rRNA-targeted oligonucleoti de probes to study changes in and the identities of sulfate-reducing b acterial populations present in enriched slurry microcosms from a pred ominantly freshwater and a predominantly marine site from the River Ta ma, Tokyo, Japan. Significant enrichment of signals from different oli gonucleotide probes, designed to target cultured members of several SR B genera, were observed in amended slurries. Signal from a probe desig ned to detect Desulfobulbus spp. gave an increased response on propion ate addition to slurries from both sites. The response to a probe desi gned to detect Desulfobacter was increased by acetate addition to slur ries from the marine site. Response to a wide specificity probe also i ncreased suggesting that uncharacterised groups were also enriched at the marine site. Our data suggest that Desulfobulbus may be an importa nt propionate utiliser in the estuary, while Desulfobacter is responsi ble for acetate utilisation at the marine site. These results are comp atible with the known physiology of Desulfobulbus and Desulfobacter an d provide strong support for the use of oligonucleotide probes in the study of microbial communities.