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

Strain 56(T) 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 MgCl(2), for growth; optimal growth occurred at > or =3.8 M (> or =22.5 %) NaCl. The strain was thermotolerant with an optimum temperature for growth of 40 degrees C, although growth was possible up to 55 degrees C. The G+C content of the DNA of the novel strain was 67.1 mol%. 16S rRNA gene sequence analysis revealed that strain 56(T) was a member of the phyletic group defined by the family Halobacteriaceae, showing the highest similarity to Halopiger xanaduensis SH-6(T) (99 %) and the next highest similarity of 94 % to other members of the family Halobacteriaceae. DNA-DNA hybridization revealed 27 % relatedness between strain 56(T) and Hpg. xanaduensis SH-6(T). Polar lipid analysis revealed the presence of the bis-sulfated glycolipid S(2)-DGD-1 as the sole glycolipid and the absence of the glycerol diether analogue phosphatidylglycerosulfate. Both C(20 x 20) and C(20 x 25) core lipids were present. Strain 56(T) accumulated large amounts of polyhydroxybutyrate and also secreted an exopolymer. Physiological and biochemical differences suggested that Hpg. xanaduanesis and strain 56(T) were sufficiently different to be separated into two distinct species. It is suggested that strain 56(T) represents a novel species of the genus Halopiger , for which the name Halopiger aswanensis sp. nov. is proposed. The type strain is strain 56(T) (=DSM 13151(T)=JCM 11628(T)).