Reclassification of Salinisphaera halophila Zhang et al. 2012 as a Later Heterotypic Synonym of Salinisphaera orenii Park et al. 2012.

In the present study, the taxonomic position of Salinisphaera halophila (NZ_AYKF00000000) and Salinisphaera orenii (NZ_AYKH00000000) was re-evaluated. In addition, their metabolic potentials and mechanisms for mitigating stress conditions were determined. Comparisons of 16S rRNA gene sequences, analysis of the phylogenetic tree, phylogenomic tree, average nucleotide identity (ANI), and digital DNA-DNA hybridization (dDDH) values were conducted. The 16S rRNA gene sequence similarity between Salinisphaera halophila YIM 95161 and Salinisphaera orenii MK-B5 was 100%. In phylogenetic and phylogenomic trees, Salinisphaera halophila YIM 95161 and Salinisphaera orenii MK-B5clustered together. Both species encode genes for glycolysis, citrate cycle, pentose phosphate pathway, Entner-Doudoroff pathway, nitrate assimilation, and assimilatory sulfate reduction. They employ salt-in and salt-out strategies to mitigate salt stress. The ANI and dDDH values between Salinisphaera halophila YIM 95161and Salinisphaera orenii MK-B5were 96.6 and 72.1%, respectively, above the cut-off (95-96% for ANI and 70% for dDDH) for species delineation. Based on the above results, we propose to reclassify Salinisphaera halophila Zhang et al. 2012 as a later heterotypic synonym of Salinisphaera orenii Park et al. 2012.