Desulfosoma caldarium gen. nov., sp. nov., a thermophilic sulfate-reducing bacterium from a terrestrial hot spring

Abstract

A thermophilic, sulfate-reducing bacterium, designated strain USBA-053T, was isolated from a terrestrial hot spring located at a height of 2500 m in the Colombian Andes (5° 45′ 33.29″ N 73° 6′ 49.89″ W), Colombia. Cells of strain USBA-053T were oval- to rod-shaped, Gram-negative and motile by means of a single polar flagellum. The strain grew autotrophically with H2 as the electron donor and heterotrophically on formate, propionate, butyrate, valerate, isovalerate, lactate, pyruvate, ethanol, glycerol, serine and hexadecanoic acid in the presence of sulfate as the terminal electron acceptor. The main end products from lactate degradation, in the presence of sulfate, were acetate, CO2 and H2S. Strain USBA-053T fermented pyruvate in the absence of sulfate and grew optimally at 57 °C (growth temperature ranged from 50 °C to 62 °C) and pH 6.8 (growth pH ranged from 5.7 to 7.7). The novel strain was slightly halophilic and grew in NaCl concentrations ranging from 5 to 30 g l−1, with an optimum at 25 g l−1 NaCl. Sulfate, thiosulfate and sulfite were used as electron acceptors, but not elemental sulfur, nitrate or nitrite. The G+C content of the genomic DNA was 56±1 mol%. 16S rRNA gene sequence analysis indicated that strain USBA-053T was a member of the class Deltaproteobacteria, with Desulfacinum hydrothermale MT-96T as the closest relative (93 % gene sequence similarity). On the basis of physiological characteristics and phylogenetic analysis, it is suggested that strain USBA-053T represents a new genus and novel species for which the name Desulfosoma caldarium gen. nov., sp. nov. is proposed. The type strain of the type species is USBA-053T ( = KCTC 5670T = DSM 22027T).