By applying the culturomics concept and using culture conditions containing a high salt concentration, we herein isolated the first known halophilic archaeon colonizing the human gut. Here we described its phenotypic and biochemical characterization as well as its genome annotation. Strain Arc-HrT (= CSUR P0974 = CECT 9307) was mesophile and grew optimally at 37 °C and pH 7. Strain Arc-HrT was also extremely halophilic with an optimal growth observed at 15% NaCl. It showed gram-negative cocci, was strictly aerobic, non-motile and non-spore-forming, and exhibited catalase and oxidase activities. The 4,015,175 bp long genome exhibits a G + C% content of 65.36% and contains 3911 protein-coding and 64 predicted RNA genes. PCR-amplified 16S rRNA gene of strain Arc-HrT yielded a 99.2% sequence similarity with Haloferax prahovense, the phylogenetically closest validly published species in the Haloferax genus. The DDH was of 50.70 ± 5.2% with H. prahovense, 53.70 ± 2.69% with H. volcanii, 50.90 ± 2.64% with H. alexandrinus, 52.90 ± 2.67% with H. gibbonsii and 54.30 ± 2.70% with H. lucentense. The data herein represented confirm strain Arc-HrT as a unique species and consequently we propose its classification as representative of a novel species belonging to the genus Haloferax, as Haloferax massiliense sp. nov.
Keywords: Culturomics; Haloferax massiliense; Halophilic archaea; Taxono-genomics.