Alicyclobacillus vulcanalis sp nov., a thermophilic, acidophilic bacterium isolated from Coso Hot Springs, California, USA

A thermo-acidophilic Gram-positive bacterium, strain CsHg2(T), which grows aerobically at 35-65 degreesC (optimum 55 degreesC) and at pH 2-0-6-0 (optimum 4-0), was isolated from a geothermal pool located in Coso Hot Springs in the Mojave Desert, California, USA. Phylogenetic analysis of 16S rRNA gene sequences showed that this bacterium was most closely related to the type strains of Alicyclobacillus acidocaldarius (97-8% identity) and Alicyclobacillus sendaiensis (96-9%), three Japanese strains denoted as UZ-1, KHA-31 and MIH 332 (96.1-96-5%) and Alicyclobacillus genomic species FR-6 (96-3%). Phenotypic characteristics including temperature and pH optima, G+C composition, acid production from a variety of carbon sources and sensitivity to different metal salts distinguished CsHg2(T) from A. acidocaldarius, A. sendaiensis and FR-6. The cell lipid membrane was composed mainly of omega-cyclohexyl fatty acid, consistent with membranes from other Alicyclobacillus species. Very low DNA-DNA hybridization values between CsHg2(T) and the type strains of Alicyclobacillus indicate that CsHg2(T) represents a distinct species. On the basis of these results, the name Alicyclobacillus vulcanalis sp. nov. is proposed for this organism. The type strain is CsHg2(T) (ATCC BAA-915(T)=DSM 16176(T)).