Haloferax litoreum sp. nov., Haloferax marinisediminis sp. nov., and Haloferax marinum sp. nov., low salt-tolerant haloarchaea isolated from seawater and sediment

Three novel halophilic archaea were isolated from seawater and sediment near Yeoungheungdo Island, Republic of Korea. The genome size and G + C content of the isolates MBLA0076 T , MBLA0077 T , and MBLA0078 T were 3.56, 3.48, and 3.48 Mb and 61.7, 60.8, and 61.1 mol%, respectively. The three strains shared 98.5–99.5 % sequence similarity of the 16 S rRNA gene, whereas their sequence similarity to the 16 S rRNA gene of type strains was below 98.5 %. Phylogenetic analysis based on sequences of the 16 S rRNA and RNA polymerase subunit beta genes indicated that the isolates belonged to the genus Haloferax . The orthologous average nucleotide identity, average amino-acid identity, and in silico DNA-DNA hybridization values were below species delineation thresholds. Pan-genomic analysis indicated that the three novel strains and 11 reference strains had 8981 pan-orthologous groups in total. Fourteen Haloferax strains shared 1766 core pan-genome orthologous groups, which were mainly related to amino acid transport and metabolism. Cells of the three isolates were gram-negative, motile, red-pink pigmented, and pleomorphic. The strains grew optimally at 30 °C (MBLA0076 T ) and 40 °C (MBLA0077 T , MBLA0078 T ) in the presence of 1.28 M (MBLA0077 T ) and 1.7 M (MBLA0076 T , MBLA0078 T ) NaCl and 0.1 M (MBLA0077 T ), 0.2 M (MBLA0076 T ), and 0.3 M (MBLA0078 T ) MgCl 2 ·6H 2 O at pH 7.0–8.0. Cells of all isolates lysed in distilled water; the minimum NaCl concentration necessary to prevent lysis was 0.43 M. The major polar lipids of the three strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, and sulphated diglycosyl archaeol-1. Based on their phenotypic and genotypic properties, MBLA0076 T , MBLA0077 T , and MBLA0078 T were described as novel species of Haloferax , for which we propose the names Haloferax litoreum sp. nov., Haloferax marinisediminis sp. nov., and Haloferax marinum sp. nov., respectively. The respective type strains of these species are MBLA0076 T (= KCTC 4288 T = JCM 34,169 T ), MBLA0077 T (= KCTC 4289 T = JCM 34,170 T ), and MBLA0078 T (= KCTC 4290 T = JCM 34,171 T ).