Halobacterium bonnevillei sp. Nov., halobaculum saliterrae sp. nov. and halovenus carboxidivorans sp. nov., three novel carbon monoxide-oxidizing halobacteria from saline crusts and soils

Abstract

Three novel carbon monoxide-oxidizing Halobacteria were isolated from Bonneville Salt Flats (Utah, USA) salt crusts and nearby saline soils. Phylogenetic analysis of 16S rRNA gene sequences revealed that strains PCN9T, WSA2T and WSH3T belong to the genera Halobacterium, Halobaculum and Halovenus, respectively. Strains PCN9T, WSA2T and WSH3T grew optimally at 40 °C (PCN9T) or 50 °C (WSA2T, WSH3T). NaCl optima were 3 M (PCN9T, WSA2T) or 4 M NaCl (WSH3T). Carbon monoxide was oxidized by all isolates, each of which contained a molybdenum-dependent CO dehydrogenase. G+C contents for the three respective isolates were 66.75, 67.62, and 63.97 mol% as derived from genome analyses. The closest phylogenetic relatives for PCN9T, WSA2T and WSH3T were Halobacterium noricense A1T, Halobaculum roseum D90T and Halovenus aranensis EB27T with 98.71, 98.19 and 95.95% 16S rRNA gene sequence similarities, respectively. Genome comparisons of PCN9T with Halobacterium noricense A1T yielded an average nucleotide identity (ANI) of 82.0% and a digital DNA–DNA hybridization (dDDH) value of 25.7%; comparisons of WSA2T with Halobaculum roseum D90T yielded ANI and dDDH values of 86.34 and 31.1%, respectively. The ANI value for a comparison of WSH3T with Halovenus aranensis EB27T was 75.2%. Physiological, biochemical, genetic and genomic characteristics of PCN9T, WSA2T and WSH3T differentiated them from their closest phylogenetic neighbours and indicated that they represent novel species for which the names Halobaculum bonnevillei, Halobaculum saliterrae and Halovenus carboxidivorans are proposed, respectively. The type strains are PCN9T (=JCM 32472=LMG 31022=ATCC TSD-126), WSA2T (=JCM 32473=ATCC TSD-127) and WSH3T (=JCM 32474=ATCC TSD-128).