Lithoautotrophic growth of the freshwater colorless sulfur bacterium Beggiatoa "leptomitiformis" D-402

The freshwater colorless sulfur bacterium Beggiatoa "leptomitiformis" D-402 was shown to be capable of lithoautotrophic growth in a batch culture under microaerobic conditions at O2 concentrations in the medium of no higher than 0.5 mg/l. The cell yield was maximum at a dissolved oxygen concentration of 0.15 mg/l. A high activity level of key enzymes of the Calvin cycle and of enzymes involved in dissimilatory oxidation of thiosulfate was recorded in the cells. The high rate of CO2 assimilation (112-139 nmol/(min mg protein)) and the cell yield (12 mg dry cells/mmol thiosulfate oxidized), 91-92% of which was accounted for by CO2 carbon, were close to those typical of autotrophic bacteria. Thiosulfate was oxidized almost completely to sulfate, and the fraction of elemental sulfur in the final products did not exceed 0.2-1.7% of the thiosulfate sulfur. The cell membrane fraction contained cytochromes (b + o) and two cytochromes c with M(r) of 23 and 26 kDa; the soluble fraction contained cytochrome c with M(r) of 12 kDa.