Bacillus subterraneus sp. nov., an iron- and manganese-reducing bacterium from a deep subsurface Australian thermal aquifer

Abstract

A facultatively anaerobic bacterium, designated strain COOI3B(T) (=ATCC BAA 136(T)=DSM 13966(T)), was isolated from the waters emitted by a bore well tapping the deep subterranean thermal waters of the Great Artesian Basin of Australia. The cells were straight to slightly curved rods (0.5--0.8 x 2--25 microm) that occurred singly and rarely in pairs or in chains. Strain COOI3B(T) was motile by peritrichous flagella. It stained Gram-negative, but electron micrographs showed a Gram-positive-type cell wall. Spores were never observed and cells were heat-sensitive. Yeast extract at 0.02% (w/v) was required for growth and could also be used as a sole carbon and energy source at concentrations higher than 0.1% (w/v). The strain utilized amorphous iron(III), manganese(IV), nitrate, nitrite and fumarate as electron acceptors in the presence of yeast extract, glucose, sucrose, fructose, maltose, xylose, starch, glycerol, ethanol or lactate. Electron acceptors were not obligately required and growth was better in the presence of nitrate than in its absence. Acid was not produced from growth on carbohydrates. Tryptophan deaminase, H(2)S, arginine dihydrolase, lysine decarboxylase, beta-galactosidase, arabinosidase, glucuronidase, glucosaminidase, nitroanilidase, xylosidase and ornithine decarboxylase were not produced. Starch and gelatin, but not casein, were hydrolysed. Aesculin and catalase, but not oxidase and urease, were produced. Strain COOI3B(T) grew optimally at temperatures between 37 and 40 degrees C (the temperature growth range was 25--45 degrees C) and at pH 7.0--9.0 (the pH growth range was 6.0 to 9.5) with 5% (w/v) NaCl (the NaCl concentration growth range was 0--9%, w/v). The DNA base composition was 43 +/- 1 mol% G+C. Phylogenetic analysis indicated that it was a member of the family Bacillaceae, Bacillus infernus and Bacillus firmus being the closest phylogenetic neighbours (having a mean similarity value of 96%); hence, strain COOI3B(T) is designated as a novel species, Bacillus subterraneus sp. nov.