sp. nov.: an extremely acidophilic sulfur-oxidizing chemolithotroph isolated from a neutral pH environment.

The genus currently includes seven species with validly published names, which fall into two major groups, those that can oxidize ferrous iron and those that do not. All seven species can use zero-valent sulfur and reduced sulfur oxy-anions as electron donors, are obligately chemolithotrophic and acidophilic bacteria with pH growth optima below 3.0. The 16S rRNA gene of a novel strain (CJ-2) isolated from circum-neutral pH mine drainage showed 95-97 % relatedness to members of the genus . Digital DNA-DNA hybridization (dDDH) values between strains and whole-genome pairwise comparisons between the CJ-2 strain and the reference genomes available for members of the genus confirmed that CJ-2represents a novel species of this genus. CJ-2 is a strict aerobe, oxidizes zero-valent sulfur and reduced inorganic sulfur compounds but does not use ferrous iron or hydrogen as electron donors. The isolate is mesophilic (optimum growth temperature 25-28 °C) and extremely acidophilic (optimum growth pH 3.0), though its pH optimum and maximum were significantly higher than those of non-iron-oxidising acidithiobacilli with validly published names. The major fatty acids of CJ-2 were C18 : 17, C:16 : 1ω7/iso-C15 : 0 2-OH, C16 : 0 and C19 : 0 cyclo ω8 and the major respiratory quinone present was Q8. The name sp. nov. is proposed, the type strain is CJ-2 (=DSM 105150=KCTC 4683).