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 PCN9 T , WSA2 T and WSH3 T belong to the genera Halobacterium , Halobaculum and Halovenus , respectively. Strains PCN9 T , WSA2 T and WSH3 T grew optimally at 40 °C (PCN9 T ) or 50 °C (WSA2 T , WSH3 T ). NaCl optima were 3 M (PCN9 T , WSA2 T ) or 4 M NaCl (WSH3 T ). 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 PCN9 T , WSA2 T and WSH3 T were Halobacterium noricense A1 T , Halobaculum roseum D90 T and Halovenus aranensis EB27 T with 98.71, 98.19 and 95.95 % 16S rRNA gene sequence similarities, respectively. Genome comparisons of PCN9 T with Halobacterium noricense A1 T yielded an average nucleotide identity (ANI) of 82.0% and a digital DNA–DNA hybridization (dDDH) value of 25.7 %; comparisons of WSA2 T with Halobaculum roseum D90 T yielded ANI and dDDH values of 86.34 and 31.1 %, respectively. The ANI value for a comparison of WSH3 T with Halovenus aranensis EB27 T was 75.2 %. Physiological, biochemical, genetic and genomic characteristics of PCN9 T , WSA2 T and WSH3 T 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 PCN9 T (=JCM 32472=LMG 31022=ATCC TSD-126), WSA2 T (=JCM 32473=ATCC TSD-127) and WSH3 T (=JCM 32474=ATCC TSD-128).