Four obligately anaerobic, thermophilic, sulfate-reducing bacterial strains, designated TGE-P1T, TDVT, TGL-LS1 and TSL-P1, were isolated from thermophilic (operated at 55 °C) methanogenic sludges from waste and wastewater treatment. The optimum temperature for growth of all the strains was in the range 55-60 °C. The four strains grew by reduction of sulfate with a limited range of electron donors, such as hydrogen, formate, pyruvate and lactate. In co-culture with the hydrogenotrophic methanogen Methanothermobacter thermautotrophicus ΔHT, strains TGE-P1T, TGL-LS1 and TSL-P1 were able to utilize lactate syntrophically for growth. The DNA G+C contents of all the strains were in the range 34-35 mol%. The major cellular fatty acids of the strains were iso-C17:0, iso-C16:0, C16:0 and anteiso-C15:0. Phylogenetic analyses based on 16S rRNA gene sequences revealed that the strains belong to the Thermodesulfovibrio clade of the phylum 'Nitrospirae'. On the basis of their physiological, chemotaxonomic and genetic properties, strains TGL-LS1 (=JCM 13214) and TSL-P1 (=ICM 13215) were classified as strains of Thermodesulfovibrio islandicus. Two novel species of the genus Thermodesulfovibrio are proposed to accommodate the other two isolates: Thermodesulfovibrio aggregans sp. nov. (type strain TGE-P1T =JCM 13213T =DSM 17283T) and Thermodesulfovibrio thiophilus sp. nov. (type strain TDVT =JCM 13216T =DSM 17215T). To examine the ecological aspects of Thermodesulfovibrio-type cells in the sludge from which the strains were originally isolated, an oligonucleotide probe targeting 16S rRNA of all Thermodesulfovibrio species was designed and applied to thin sections of thermophilic sludge granules. Fluorescence in situ hybridization using the probe revealed rod- or vibrio-shaped cells as a significant population within the sludge, indicating their important role in the original ecosystem.
|ジャーナル||International journal of systematic and evolutionary microbiology|
|出版ステータス||Published - 2008 11月|
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