Genome-based reclassification of Chromohalobacter japonicus Sánchez-Porro et al. 2007 as a later heterotypic synonym of Chromohalobacter beijerinckii Peçonek et al. 2006.

In this study, whole-genome analyses were employed to resolve the taxonomic status of two closely related Chromohalobacter species. Among the eight type strains with publicly available data, C. beijerinckii Peçonek et al. (Int J Syst Evol Microbiol 56:1953-1957, 2006) and C. japonicus Sánchez-Porro et al. (Int J Syst Evol Microbiol 57:2262-2266, 2007) repeatedly converged as a single evolutionary unit. The 16S rRNA gene sequences of C. beijerinckii ATCC 19372 T and C. japonicus 43 T possess 99.26% sequence similarity. Furthermore, whole-genome sequence comparisons showed that C. beijerinckii DSM 7218 T and C. japonicus CECT 7219 T shared 96.82% BLAST-based average nucleotide identity (ANIb), 97.69% average amino acid identity (AAI) and 73.1% digital DNA-DNA hybridization (dDDH) values. Although originally described as distinct taxa, these results exceed the criteria for species-level differentiation, confirming that both strains belong to the same species. Phylogenomic reconstruction of core genes further highlighted their placement in one robust clade. Overall, the combined analyses support the conclusion that C. japonicus Sánchez-Porro et al. (Int J Syst Evol Microbiol 57:2262-2266, 2007) is a later heterotypic synonym of C. beijerinckii Peçonek et al. (Int J Syst Evol Microbiol 56:1953-1957, 2006).