Haloarchaea are among the dominant microorganisms present in hypersaline habitats.They are represented by a diverse group of extremely halophilic aerobic archaea,included in the class Halobacteria,and currently classified within 49 genera and nearly 100 species.The genus Halorubrum comprises 28 species being the haloarchaeal genus with a higher number of species and probably the most widely distributed in saline habitats.Recent metagenomic studies in saltem ponds with intermediate salinities and on saline soils indicated that a large proportion of the metagenomic sequences corresponded to no-yet-cultivated prokaryotes,including taxa related to Halorubrum and to other archaea.In this study,we have isolated and characterized a large number of haloarchaeal stains and specifically we focused on the isolated related to the genus Halorubrura in order to determine its biodiversity.In particular two new isolates,strains SD626 and SD645,have been studied in detail.They presented a 99.3%16S rRNA gene sequence similarity with the type strain ofHalorubrum salinum and high similarities with several other species of Halorubrum.However,a detailed multilocus sequence analysis based on the comparison of four housekeeping genes(atpB,EF-2,glnaA and rpoB)clearly supported the affiliation of these two new strains as a new species of the genus Halorubrwn.We have carried out the sequencing of the genome of strain SD626 and the ANI values with respect to the most closely related species confirmed the new species status of this strain.Besides,a taxonomic polyphasic study including a phenotypic,genotypic and chemotaxonomic characterization has been performed.On the basis of these results we propose the name of Halorubrum grantii sp.nov.,for this new taxon.On the other hand,another six recent isolates obtained from saline soils may also represent two new species of the genus Halorubrum.The comparison of the complete genome of strain SD626,as a representative of the new species Hrr.grantii,with the metagenomic databases currently available indicated that this new taxon is abundant in ponds of salterns with intermediated salinities(with 19 to 21%total salts),as well as saline lakes and saline soils.