Thermotoga lettingae sp. nov. : a novel thermophilic, methanol-degrading bacterium isolated from a thermophilic anaerobic reactor

A novel, anaerobic, non-spore-forming, mobile, Gram-negative, thermophilic bacterium, strain TMO(T), was isolated from a thermophilic sulfate-reducing bioreactor operated at 65 degrees C with methanol as the sole substrate. The G C content of the DNA of strain TMO(T) was 39.2 molÐThe optimum pH, NaCl concentration, and temperature for growth were 7.0, 1.0°and 65 degrees C, respectively. Strain TMO(T) was able to degrade methanol to CO(2) and H(2) in syntrophic culture with Methanothermobacter thermautotrophicus DeltaH or Thermodesulfovibrio yellowstonii. Thiosulfate, elemental sulfur, Fe(III) and anthraquinone-2,6-disulfonate were able to serve as electron acceptors during methanol degradation. In the presence of thiosulfate or elemental sulfur, methanol was converted to CO(2) and partly to alanine. In pure culture, strain TMO(T) was also able to ferment methanol to acetate, CO(2) and H(2). However, this degradation occurred slower than in syntrophic cultures or in the presence of electron acceptors. Yeast extract was required for growth. Besides growing on methanol, strain TMO(T) grew by fermentation on a variety of carbohydrates including monomeric and oligomeric sugars, starch and xylan. Acetate, alanine, CO(2), H(2), and traces of ethanol, lactate and alpha-aminobutyrate were produced during glucose fermentation. Comparison of 16S rDNA genes revealed that strain TMO(T) is related to Thermotoga subterranea (98€and Thermotoga elfii (98Ž The type strain is TMO(T) (=DSM 14385(T)=ATCC BAA-301(T)). On the basis of the fact that these organisms differ physiologically from strain TMO(T), it is proposed that strain TMO(T) be classified as a new species, within the genus Thermotoga, as Thermotoga lettingae.