New organic substrates for anoxygenic phototrophic bacteria

For the first time, a purple sulfur bacterium (strain E3P) able to utilize AH2QDS and reduced humic acids was isolated. 16S rRNA gene sequence of strain E3P showed the closest relative with Thiocystis violacea (95.8%). AQDS and humic acids were also shown to serve as electron shuttles between the chemotrophic Geobacter metallireducens and strain E3P. Enrichments from marine sediments with n-hexane and n-decane as substrates for anoxygenic phototrophic bacteria were established. Analysis of the enriched microbial communities by DGGE revealed phylotypes closely related to described anoxygenic phototrophic and sulfate-reducing bacteria. Results suggest that sulfate-reducing bacteria in the enrichment culture coupled the degradation of n-hexane or n-decane to the reduction of sulfate to sulfide. The latter could be used by phototrophic bacteria.A phototrophic strain utilizing toluene was isolated (strain GH1). This strain shared 99% 16S rRNA gene sequence similarity and 92.7% DNA-DNA similarity with a described toluene-utilizing phototrophic bacterium, Blastochloris sulfoviridis strain ToP1. In both strains, the gene bssA was detected.