Anoxybacillus calidus sp. nov., a thermophilic bacterium isolated from soil near a thermal power plant.

A novel thermophilic, Gram-stain-positive, facultatively anaerobic, endospore-forming, motile, rod-shaped bacterium, strain C161ab(T), was isolated from a soil sample collected near Kizildere, Saraykoy-Buharkent power plant in Denizli. The isolate could grow at temperatures between 35 and 70 °C (optimum 55 °C), at pH 6.5-9.0 (optimum pH 8.0-8.5) and with 0-2.5 % NaCl (optimum 0.5 %, w/v). The strain formed cream-coloured, circular colonies and tolerated up to 70 mM boron. Its DNA G+C content was 37.8 mol%. The peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid. Strain C161ab(T) contained menaquinones MK-7 (96 %) and MK-6 (4 %). The major cellular fatty acids were iso-branched fatty acids: iso-C15 : 0 (52.2 %) and iso-C17 : 0 (28.0 %,) with small amounts of C16 : 0 (7.4 %). Phylogenetic analysis based on the 16S rRNA gene revealed 94.6-96.8 % sequence similarity with all recognized species of the genus Anoxybacillus. Strain C161ab(T) showed the greatest sequence similarity to Anoxybacillus rupiensis DSM 17127(T) and Anoxybacillus voinovskiensis DSM 17075(T), both had 96.8 % similarity to strain C161ab(T), as well as to Anoxybacillus caldiproteolyticus DSM 15730(T) (96.6 %). DNA-DNA hybridization revealed low levels of relatedness with the closest relatives of strain C161ab(T), A. rupiensis (21.2 %) and A. voinovskiensis (16.5 %). On the basis of the results obtained from phenotypic, chemotaxonomic, genomic fingerprinting, phylogenetic and hybridization analyses, the isolate is proposed to represent a novel species, Anoxybacillus calidus sp. nov. (type strain C161ab(T) = DSM 25520(T) = NCIMB 14851(T)).