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 degrees C (MBLA0076(T)) and 40 degrees 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)) MgCl2 center dot 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)).

Automated summary

Three novel halophilic archaea, isolated from seawater and sediment near Yeoungheungdo Island in Korea, belong to the genus Haloferax, with similarities and differences in their genetic properties. They thrive in high-salt environments and exhibit specific physiological and metabolic characteristics.