A Gram-negative, aerobic, neutrophilic and extremely halophilic archaeon (strain AJ201 T ), isolated from Ayakekum salt lake on the Qinghai-Tibet Plateau, was investigated by a polyphasic approach. The DNA G+C content of strain AJ201 T was 65.7 mol%. The major polar lipid profile and phylogenetic analysis based on 16S rRNA gene sequences supported the allocation of the strain to the genus Halorubrum. The results of DNA-DNA hybridizations and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain AJ201 T from closely related species. Therefore, strain AJ201 T represents a novel species of the genus Halorubrum, for which the name Halorubrum arcis sp. nov. is proposed. The type strain is strain AJ201 T (=CGMCC 1.5343 T =JCM 13916 T ). (McGenity & Grant, 1995;Kamekura & Dyall-Smith, 1995) are widely distributed in hypersaline habitats (Grant & Larsen, 2001). At the time of writing, there are 16 species with validly published names in the genus Halorubrum, including three alkaliphilic species, Halorubrum vacuolatum (Mwatha & Grant, 1993; Kamekura et al., 1997), Hrr. tibetense (Fan et al., 2004) and Hrr. alkaliphilum (Feng et al., 2005), and 13 neutrophilic species, Halorubrum saccharovorum (the type species; Tomlinson & Hochstein, 1976), Hrr. sodomense (Oren, 1983, Hrr. lacusprofundi (Franzmann et al., 1988), Hrr. coriense (Nuttall & Dyall-Smith, 1993), Hrr. trapanicum (McGenity & Grant, 1995; Trüper, 2003), Hrr. distributum (Zvyagintseva & Tarasov, 1987;Oren & Ventosa, 1996) (Cui et al., 2006). Here, we report the taxonomic characterization of a neutrophilic strain belonging to the genus Halorubrum.
Members of the genus HalorubrumStrain AJ201 T was isolated from mud of Ayakekum salt lake (37u 379 N 89u 299 E; 3884 m altitude) located in the Altun Mountain, in the northern part of the Qinghai-Tibet Plateau. The lake environment was described previously in detail (Xu et al., 2005a). The sample was incubated with S-G medium (Sehgal & Gibbons, 1960) for approximately 1 week and the liquid was plated by using a tenfold dilution series method. After 1-2 weeks of incubation at 37 u C, a representative red colony was picked and maintained on S-G medium. The strain was purified by repeated restreaking; purity was confirmed by the uniformity of cell morphology. The optimal conditions for growth were determined in S-G medium modified with 0.85-5.1 M NaCl or 0-1.0 M Mg 2+ .Phenotypic tests and lipid analysis were performed according to Xu et al. (2005b) as mentioned previously in the minimal standards for the description of new taxa in the order Halobacteriales (Oren et al., 1997). Detailed results of cell morphology, physiological tests and antibiotic sensitivity are given in the species description. The major polar lipids of strain AJ201 T were determined to be C 20 C 20 derivatives of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and sulfated mannosyl-glucosyl-glycerol diether ( Supplementary Fig. S1 in IJSEM Online).The 16S rRNA ge...