Reclassification of ‘Sulfobacillus thermosulfidooxidans subsp. thermotolerans’ strain K1 as Alicyclobacillus tolerans sp. nov. and Sulfobacillus disulfidooxidans Dufresne et al. 1996 as Alicyclobacillus disulfidooxidans comb. nov., and emended description of the genus Alicyclobacillus

Abstract

Comparative analysis of 16S rRNA gene sequences, DNA–DNA hybridization data and phenotypic properties revealed that ‘Sulfobacillus thermosulfidooxidanssubsp.thermotolerans’ strain K1 is not a member of the genusSulfobacillus. Phylogenetically, strain K1 is closely related to unclassified strains of the genusAlicyclobacillus: the 16S rRNA gene sequence of strain K1 is similar to that ofAlicyclobacillussp. AGC-2 (99·6 %),Alicyclobacillussp. 5C (98·9 %) andAlicyclobacillussp. CLG (98·6 %) and bacterium GSM (99·1 %). The 16S rRNA gene sequence similarity values for strain K1 and species of the genusAlicyclobacilluswith validly published names were in the range 92·1–94·6 %, and forS. thermosulfidooxidansVKM B-1269Tthe value was 87·7 %.Sulfobacillus disulfidooxidansSD-11Twas also phylogenetically related to strain K1 (92·6 % sequence similarity) and thus belonged to the genusAlicyclobacillus. Chemotaxonomic data, such as the major cell-membrane lipid components of strains K1 and SD-11T(ω-alicyclic fatty acids) and the major isoprenoid quinone (menaquinone MK-7) of strain K1, supported the affiliation of strains K1 and SD-11Tto the genusAlicyclobacillus. Physiological and molecular biological tests allowed genotypic and phenotypic differentiation of strains K1 and SD-11Tfrom the nineAlicyclobacillusspecies with validly published names. The G+C content of the DNA of strain K1 was 48·7±0·6 mol%; that of strain SD-11Twas 53±1 mol%. DNA–DNA reassociation studies showed low relatedness (22 %) between strains K1 and SD-11T, and even lower relatedness (3–5 %) between these strains andAlicyclobacillus acidocaldariussubsp.acidocaldariusATCC 27009T, DSM 446T. DNA reassociation of strains K1 and SD-11TwithAlicyclobacillus cycloheptanicusDSM 4006Tgave values of 15 and 21, respectively. Based on the phenotypic and phylogenetic characteristics of strains K1 and SD-11T,Alicyclobacillus toleranssp. nov. (type strain, K1T=VKM B-2304T=DSM 16297T) andAlicyclobacillus disulfidooxidanscomb. nov. (type strain, SD-11T=ATCC 51911T=DSM 12064T) are proposed.