Halopiger aswanensis sp. nov., a polymer-producing and extremely halophilic archaeon isolated from hypersaline soil

Abstract

Strain 56T was isolated from a hypersaline soil in Aswan (Egypt). Cells were pleomorphic rods. The organism was neutrophilic, motile and required at least 1.7 M (10 % w/v) NaCl, but not MgCl2, for growth; optimal growth occurred at ≥3.8 M (≥22.5 %) NaCl. The strain was thermotolerant with an optimum temperature for growth of 40 °C, although growth was possible up to 55 °C. The G+C content of the DNA of the novel strain was 67.1 mol%.16S rRNA gene sequence analysis revealed that strain 56T was a member of the phyletic group defined by the family Halobacteriaceae, showing the highest similarity to Halopiger xanaduensis SH-6T (99 %) and the next highest similarity of 94 % to other members of the family Halobacteriaceae. DNA–DNA hybridization revealed 27 % relatedness between strain 56T and Hpg. xanaduensis SH-6T. Polar lipid analysis revealed the presence of the bis-sulfated glycolipid S2-DGD-1 as the sole glycolipid and the absence of the glycerol diether analogue phosphatidylglycerosulfate. Both C20 . 20 and C20 . 25 core lipids were present. Strain 56T accumulated large amounts of polyhydroxybutyrate and also secreted an exopolymer. Physiological and biochemical differences suggested that Hpg. xanaduanesis and strain 56T were sufficiently different to be separated into two distinct species. It is suggested that strain 56T represents a novel species of the genus Halopiger, for which the name Halopiger aswanensis sp. nov. is proposed. The type strain is strain 56T (=DSM 13151T=JCM 11628T).