Halogeometricum rufum sp. nov., a halophilic archaeon from a marine solar saltern, and emended description of the genus Halogeometricum

Two halophilic archaea, strains RO1-4T and RO1-64, were isolated from a marine solar saltern in Jiangsu, China. Cells of the two strains were pleomorphic, motile, and stained Gram-negative. Colonies were red-pigmented. Strains RO1-4T and RO1-64 were able to grow at 25–55 °C (optimum 40–42 °C), at 2.1–5.1 M NaCl (optimum 3.9 M NaCl), at 0.05–0.7 M MgCl2 (optimum 0.3 M MgCl2) and at pH 6.0–8.5 (optimum pH 7.0). Cells lyse in distilled water and the minimal NaCl concentration to prevent cell lysis is 12 % (w/v). On the basis of 16S rRNA gene sequence analysis, strains RO1-4T and RO1-64 were closely related to Halogeometricum borinquense PR3T (98.0 and 98.2 % similarity, respectively) and Halosarcina pallida BZ256T (97.8 and 97.9 %). The major polar lipids of the two strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and two glycolipids (S-DGD-1 and DGD-1). The DNA G+C contents of strains RO1-4T and RO1-64 are 64.9 and 62.4 mol%, respectively. The DNA–DNA hybridization value between strains RO1-4T and RO1-64 was 83.0 % and both strains showed low DNA–DNA relatedness with Halogeometricum borinquense PR3T (42.5 and 50.1 % relatedness, respectively) and Halosarcina pallida BZ256T (37.6 and 42.1 % relatedness). It was concluded that strains RO1-4T and RO1-64 represent a novel species of the genus Halogeometricum, for which the name Halogeometricum rufum sp. nov. is proposed. The type strain is RO1-4T (=CGMCC 1.7736T =JCM 15770T).