THIOSULFATE METABOLISM IN THE AEROBIC BACTERIOCHLOROPHYLL-A-CONTAINING BACTERIA - ERYTHROMICROBIUM-HYDROLITICUM AND ROSEOCOCCUS-THIOSULFATOPHILUS

Two out of seven tested aerobic freshwater bacteria containing bacteri ochlorophyll a were shown to oxidize thiosulfate in the dark and in th e light. Erythromicrobium hydroliticum oxidized thiosulfate to tetrath ionate; and Roseococcus thiosulfatophilus, to sulfate. Addition of thi osulfate (up to 3 g/liter) to the medium resulted in biomass increase in the above species by 13 and 44%, respectively, and stimulated respi ration of cells. Cell extracts of E. hydroliticum contained the enzyme oxidizing thiosulfate to tetrathionate. Cell extracts of R. thiosulfa tophilus contained thiosulfate reductase and sulfite: cytochrome c oxi doreductase, which participate in dissimilatory metabolism of thiosulf ate. Adenosine-5-phosphosulfate reductase was not detected in either o f the species. None of the seven strains of erythrobacteria was able t o oxidize sulfide. The resulting data indicate that the studied erythr obacteria are capable of chemolithoheterotrophy.