Haloprofundus marisrubri gen. nov., sp. nov., an extremely halophilic archaeon isolated from the Discovery Deep brine-seawater interface in the Red Sea.

We isolated a Gram-staining-negative, pink-pigmented, motile, pleomorphic, extremely halophilic archaeon from the brine-seawater interface of Discovery Deep in the Saudi Arabian Red Sea. This strain, designated SB9T, is capable of growth within a wide range of temperatures and salinity concentrations, but requires MgCl2. Cells lyse in distilled water, but at 7.0% NaCl (w/v) cell lysis is prevented. The major polar lipids from strain SB9T are phosphatidylglycerol (PG), phosphatidylglycerorophosphate-methylester (PGP-Me), sulfated mannosyl glucosyl diether (S-DGD-1), mannosyl glucosyl diether (DGD-1), unidentified glycolipid (GL1) and unidentified phospholipids (UPL1 and UPL2). The major respiratory quinones of strain SB9T are MK8 (66%) and MK8 (VIII-H2) (34%). Analysis of 16S rRNA gene sequence revealed that strain SB9T is closely related to species in the genus Halogranum and Haloplanus, in particular, it shares the highest sequence similarity with Halogranum rubrum (93.4%), making it its closest known relative. The unfinished draft genome of strain SB9T is 3,931,127 bp in size with a total GC content of 62.53 mol% and contains 3,917 ORFs, 50 tRNAs, and 8 rRNAs. Based on comparisons with currently available genomes, the highest average nucleotide identity (ANI) value was 83% to Halogranum salarium B-1T (GenBank accession No. GCA_000283335.1). These data indicate that this new isolate cannot be classified into any recognised genera of the family Haloferacaceae, and therefore, strain SB9T is considered to be a representative of a novel genus within this family. We propose the name Haloprofundus marisrubri gen. nov., sp. nov. to describe strain SB9T (=JCM 19565T = CGMCC 1.14959 T).