BIODIVERSITY OF THERMOPHILIC SULFUR-REDUCING BACTERIA - NEW SUBSTRATES AND NEW HABITATS

Five strains of thermophilic sulfur-reducing bacteria were isolated fr om continental hot springs in Kamchatka and from shallow-water submari ne hot vents in New Guinea and New Zealand. Cells of all isolates were short rods, sometimes occurring in pairs. All strains but one were mo tile, having a polar flagellum. The optimal growth temperature was 53- 58 degrees C, and the optimal pH for growth was 5.8-7.0. The three mar ine strains required 2.5% NaCl for growth. All isolates were strict an aerobes and reduced elemental sulfur to hydrogen sulfide. Elemental su lfur was obligately required for growth by all but the propionate-util izing strain, which could also grow with thiosulfate as an acceptor or , in the presence of pyruvate, without any acceptor. As a source of en ergy, all strains were found to utilize molecular hydrogen, acetate, a nd saturated fatty acids; one marine strain could also grow on ethanol . In addition, two Kamchatka strains grew on lactate, pyruvate, malate , and fumarate. All substrates tested were oxidized completely, with t he only end products of metabolism being CO2 and H2S. The results obta ined reveal a wide distribution of thermophilic sulfur-reducing bacter ia in different thermal habitats and indicate the wide catabolic poten tial of this group of thermophilic anaerobes.