Bacillus horneckiae sp. nov., isolated from a spacecraft-assembly clean room

Abstract

Five Gram-stain-positive, motile, aerobic strains were isolated from a clean room of the Kennedy Space Center where the Phoenix spacecraft was assembled. All strains are rod-shaped, spore-forming bacteria, whose spores were resistant to UV radiation up to 1000 J m−2. The spores were subterminally positioned and produced an external layer. A polyphasic taxonomic study including traditional biochemical tests, fatty acid analysis, cell-wall typing, lipid analyses, 16S rRNA gene sequencing and DNA–DNA hybridization studies was performed to characterize these novel strains. 16S rRNA gene sequencing and lipid analyses convincingly grouped these novel strains within the genus Bacillus as a cluster separate from already described species. The similarity of 16S rRNA gene sequences among the novel strains was >99 %, but the similarity was only about 97 % with their nearest neighbours Bacillus pocheonensis, Bacillus firmus and Bacillus bataviensis. DNA–DNA hybridization dissociation values were <24 % to the closest related type strains. The novel strains had a G+C content 35.6±0.5 mol% and could liquefy gelatin but did not utilize or produce acids from any of the carbon substrates tested. The major fatty acids were iso-C15 : 0 and anteiso-C15 : 0 and the cell-wall diamino acid was meso-diaminopimelic acid. Based on phylogenetic and phenotypic results, it is concluded that these strains represent a novel species of the genus Bacillus, for which the name Bacillus horneckiae sp. nov. is proposed. The type strain is 1P01SCT (=NRRL B-59162T =MTCC 9535T).