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Phylogenomic analysis shows that 'Bacillus vanillea' is a later heterotypic synonym of Bacillus siamensis

Dunlap, Christopher A.
International journal of systematic and evolutionary microbiology 2015 v.65 no.10 pp. 3507-3510
Bacillus (bacteria), chemotaxonomy, genome, genomics, nucleic acid hybridization, odor compounds, phenotype, phylogeny, sequence analysis, strains, taxonomic revisions, vanilla beans
‘Bacillus vanillea’ XY18T (=CGMCC 8629 T =NCCB 100507 T) was isolated from cured vanilla beans and involved in the formation of vanilla aroma compounds. A draft genome of this type strain was assembled and yielded a length of 3.72 Mbp and a GC content of 46.3%. Comparative genomic analysis with its nearest relatives showed only minor differences between this strain and the genome of the Bacillus siamensis KCTC 13613**T (=BCC 22614**T), with a calculated DNA-DNA hybridization (DDH) value of 91.2%. This DDH value is well above the recommended 70% threshold for species delineation. In addition, the results of morphological, physiological, chemotaxonomic and phylogenetic analyses indicate that the type strains of these two taxa are highly similar with phenotype coherence. A core genome multilocus sequencing analysis was conducted for the strains and the results show that the type strain of ‘B. vanillea’ clusters closely to B. siamensis type strain. Therefore, it is proposed that the species ‘Bacillus vanillea’ should be reclassified as a later heterotypic synonym of Bacillus siamensis.