Reclassification of Halomicroarcula saliterrae Straková et al. 2024 and Halomicroarcula onubensis Straková et al. 2024 into the genus Haloarcula, as Haloarcula saliterrae comb. nov. and Haloarcula onubensis comb. nov., respectively

The haloarchaeal genera <i>Halomicroarcula</i> and <i>Haloarcula</i>, belonging to the family <i>Haloarculaceae</i>, order <i>Halobacteriales</i>, class <i>Halobacteria</i>, within the phylum <i>Methanobacteriota</i>, have previously exhibited significant phylogenetic and taxonomic overlaps. This issue was recently resolved by merging the two genera into a single genus, <i>Haloarcula</i>. However, <i>Halomicroarcula saliterrae</i> and <i>Halomicroarcula onubensis</i> were described almost simultaneously with the proposal to unify the genera <i>Haloarcula</i> and <i>Halomicroarcula</i>. Their names were validly published under the International Code of Nomenclature of Prokaryotes (ICNP) according to Validation List no. 217, alongside six <i>Haloarcula</i> species and the transfer of the existing <i>Halomicroarcula</i> species into the genus <i>Haloarcula</i>. Therefore a phylogenetic, phylogenomic, and comparative genomic analysis was carried out to clarify the taxonomic status of these two haloarchaeal species, <i>Halomicroarcula saliterrae</i> and <i>Halomicroarcula onubensis</i>, with lower priority than the six new species of the genus <i>Haloarcula</i>. Phylogenetic studies of 16S rRNA and <i>rpoB'</i> gene sequences, along with phylogenomic reconstructions using single-copy core-orthologous proteins, indicated that the two species clustered with the members of the genus <i>Haloarcula</i>. The overall genome relatedness indexes (OGRIs), comparative analyses of phenotypic features, and polar lipid profiles further supported their taxonomic reassignment as two separate species within the genus <i>Haloarcula</i>. Consequently, we propose the reclassification of <i>Halomicroarcula saliterrae</i> Straková <i>et al</i>. 2024 and <i>Halomicroarcula onubensis</i> Straková <i>et al</i>. 2024 into the genus <i>Haloarcula</i>, as <i>Haloarcula saliterrae</i> comb. nov. and <i>Haloarcula onubensis</i> comb. nov., respectively, in accordance with the ICNP.