Aerobic sulfur-oxidizing and anaerobic phototrophic sulfide-oxidizing bacteria were enriched trom ferrous-containing groundwater and anoxic sediment from Ba Mau lake, using mineral media with thiosulfate and sulfide as electron donors. Two strains T3 (aerobic) and P7 (anaerobic, phototroph) were isolated and purified from these enrichment cultures under oxic and anoxic conditions, respectively. Strain T3 oxidized sulfide to sulfate that accumulated in the culture medium and lowered its pH, whereas strain P7 converted sulfide to sulfur deposited in the form of granules inside the cells and could be visible under microscopy. Both strains showed high activity in the oxidation of sulfide (at the inhibitory concentrations to many other species) under aerobic and anaerobic conditions, respectively. In particular, strain P7 was able to grow in the medium supplemented with sulfide at the concentration as high as 9 mM and was inhibited only at the concentration of 15 mM. Based on the l6S rDNA sequence data, strains T3 and P7 were accordingly designated as Thiobacillus sp. T3 and Allochromatium sp. P7. The obtained results indicated the application potential of the strains T3 and P7 for the treatment of sulfide in contaminated sources.