Description of Anaerobaculum hydrogeniformans sp nov., an anaerobe that produces hydrogen from glucose, and emended description of the genus Anaerobaculum

A novel anaerobic, moderately thermophilic, NaCl-requiring fermentative bacterium, strain OS1(T), was isolated from oil production water collected from Alaska, USA. Cells were Gram-negative, non-motile, non-spore-forming rods (1.7-2.7 x 0.4-0.5 mu m). The G + C content of the genomic DNA of strain OS1(T) was 46.6 mol%. The optimum temperature, pH and NaCl concentration for growth of strain OS1(T) were 55 degrees C, pH 7 and 10 g l(-1), respectively. The bacterium fermented D-fructose, D-glucose, maltose, D-mannose, alpha-ketoglutarate, L-glutamate, malonate, pyruvate, L-tartrate, L-asparagine, Casamino acids, L-cysteine, L-histidine, L-leucine, L-phenylalanine, L-serine, L-threonine, L-valine, inositol, inulin, tryptone and yeast extract. When grown on D-glucose, 3.86 mol hydrogen and 1.4 mol acetate were produced per mol substrate. Thiosulfate, sulfur and L-cystine were reduced to sulfide, and crotonate was reduced to butyrate with glucose as the electron donor. 16S rRNA gene sequence analysis indicated that strain OS1(T) was related to Anaerobaculum thermoterrenum (99.7% similarity to the type strain), a member of the phylum Synergistetes. DNA-DNA hybridization between strain OS1(T) and A. thermoterrenum DSM 13490(T) yielded 68% relatedness. Unlike A. thermoterrenum, strain OS1(T) fermented malonate, maltose, tryptone, L-leucine and L-phenylalanine, but not citrate, fumarate, lactate, L-malate, glycerol, pectin or starch. The major cellular fatty acid of strain OS1(T) was iso-C-15:0 (91% of the total). Strain OS1(T) also contained iso-C-13:0 3-OH (3%), which was absent from A. thermoterrenum, and iso-C-13:0 (2%), which was absent from Anaerobaculum mobile. On the basis of these results, strain OS1(T) represents a novel species of the genus Anaerobaculum, for which the name Anaerobaculum hydrogeniformans sp. nov. is proposed. The type strain is OS1(T) (=DSM 22491(T) =ATCC BAA-1850(T)). An emended description of the genus Anaerobaculum is also given.