Bacillus aerius sp. nov., Bacillus aerophilus sp. nov., Bacillus stratosphericus sp. nov. and Bacillus altitudinis sp. nov., isolated from cryogenic tubes used for collecting air samples from high altitudes

Abstract

Four novel bacterial strains were isolated from cryogenic tubes used to collect air samples at altitudes of 24, 28 and 41 km. The four strains, 24K^T, 28K^T, 41KF2a^T and 41KF2b^T, were identified as members of the genus Bacillus. Phylogenetic analysis based on 16S rRNA gene sequences indicated that three of the strains, 24K^T, 28K^T and 41KF2a^T, are very similar to one another (>98% sequence similarity) and show a similarity of 98-99% with Bacillus licheniformis and 98% with Bacillus sonorensis. DNA-DNA hybridization studies showed that strains 24K^T, 28K^T and 41KF2a^T exhibit <70% similarity with each other and with B. licheniformis and B. sonorensis. Differences in phenotypic and chemotaxonomic characteristics between the novel strains and B. licheniformis and B. sonorensis further confirmed that these three isolates are representatives of three separate novel species. Strain 41KF2b^T showed 100% 16S rRNA gene sequence similarity to Bacillus pumilus, but differed from its nearest phylogenetic neighbour in a number of phenotypic and chemotaxonomic characteristics and showed only 55% DNA-DNA relatedness. Therefore, the four isolates represent four novel species for which the names Bacillus aerius sp. nov. (type strain, 24K^T=MTCC 7303^T=JCM 13348^T), Bacillus aerophilus sp. nov. (type strain, 28K^T=MTCC 7304^T=JCM 13347^T), Bacillus stratosphericus sp. nov. (type strain, 41KF2a^T=MTCC 7305^T=JCM 13349^T) and Bacillus altitudinis sp. nov. (type strain, 41KF2b^T=MTCC 7306^T=JCM 13350^T) are proposed.