Sulfate‐reducing bacteria in the periodontal pocket

This report is the first to describe the occurrence of sulfate-reducing bacteria in the human mouth. Samples of subgingival dental plaque were examined for the presence of sulfate-reducing bacteria. Using enrichment cultures, sulfate-reducing bacteria were detected in 25 (58%) of 43 individuals, and in 39 (48%) of the 82 samples. Pure isolates of sulfate-reducing bacteria, obtained from a limited number of enrichment cultures, belonged to the genera Desulfobacter and Desulfovibrio. These genera are also the predominant sulfate-reducing bacteria in the human large intestine. The sulfate-reducing bacteria use sulfate as terminal electron acceptor to oxidize low-molecular-weight organic compounds, mainly products of microbial fermentation such as acetate, lactate etc. The numbers of sulfate-reducing bacteria in the mouth are assumed to be limited by sulfate. Potential sources of sulfate in the subgingival area include free sulfate in pocket fluid and glycosaminoglycans from periodontal tissues.