Comparative genomics of the genus Halioglobus reveals the genetic basis for the reclassification of Halioglobus pacificus as Parahalioglobus pacificus gen. nov. comb. nov.

Abstract

The genus Halioglobus is one of the environmentally relevant members of the family Halieaceae, class Gammaproteobacteria. At present, the genus is composed of three validly published species. However, in the recent study of the family Halieaceae, the species Halioglobus pacificus was observed to branch outside of the main clade formed by the members of Halioglobus, suggesting its distinct taxonomic placement within the family. In the present study, the taxonomic placement of H. pacificus was reassessed using comparative genomics. Phylogenomic analysis revealed the paraphyletic relationship of H. pacificus with the type species of the genus Halioglobus, and further demonstrated its genus-level placement. This phylogenetic relationship was reinforced by the average nucleotide and amino acid identity values shared by H. pacificus with the members of the family Halieaceae. Moreover, the results of the pan-genome analysis, together with the phenotype data, further supported the exclusion of H. pacificus from the genus Halioglobus. Based on these findings, the species H. pacificus is thereby assigned to a new genus Parahalioglobus gen. nov. as Parahalioglobus pacificus comb. nov.