Bacillus safensis subsp. osmophilus subsp. nov., isolated from condensed milk, and description of Bacillus safensis subsp. safensis subsp. nov

Abstract

A bacterial strain, designated BC09^T, was isolated from a contaminated sample of condensed milk. Phylogenetic analyses based on 16S rRNA gene sequences placed strain BC09^T into the genus Bacillus with its closest relatives being Bacillus safensis and Bacillus australimaris with 100 and 99.9 % similarity, respectively. Analysis of the gyrB gene confirmed the closeness of strain BC09^T with respect to the species B. safensis since it presented 97.8 and 95.2 % similarity values, respectively, to the type strains of B. safensis and B. australimaris. DNA-DNA hybridization confirmed these results showing averages of 67 and 56 %, respectively, between strain BC09^T and the type strains of B. safensis and B. australimaris. Average nucleotide identity blast values obtained for BC09^T compared to the closest relative type strains were 95.7 and 67.6 %, respectively, and predicted DNA-DNA hybridization values were 93.1 and 51.9 %, respectively. However, strain BC09^T differs from the type strains of its closest relatives in several phenotypic characteristics. MK-7 was the only menaquinone detected and iso-C15:0 and anteiso-C15:0 were the major fatty acids. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, two unidentified phospholipids, two unidentifed glycolipids, three unidentified lipids and one unidentifed phosphoglycolipid. Meso-diaminopimelic acid was detected in the peptidoglycan. The G+C content was 40.9 mol%. Phylogenetic, chemotaxonomic and phenotypic analyses showed that strain BC09^T represents a new subspecies of B. safensis, for which the name Bacillus safensis subsp. osmophilus subsp. nov. is proposed. The type strain is BC09^T (=LMG 30124^T, =CECT 9344^T).

Keywords: Bacillus; Bacillus safensis; Spain; milk.