Halalkalicoccus tibetensis gen. nov., sp. nov., representing a novel genus of haloalkaliphilic archaea Yanfen Xue, 1 Huapeng Fan, 1 Antonio Ventosa, 2 William D. Grant, 3 Brian E. Jones, 4 Don A. Cowan 5 and Yanhe Ma 1 Correspondence Yanhe Ma mayanhe@sun.im.ac.cn 1 State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, China 2 Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Sevilla, 41012 Seville, Spain 3 Department of Infection, Immunity and Inflammation, University of Leicester, Leicester LE1 9HN, UK 4 Genencor International BV, Archimedesweg 30, 2333 CN Leiden, The Netherlands 5 Department of Biotechnology, University of the Western Cape, Bellville, 7535, South Africa A haloalkaliphilic archaeon (strain DS12 T ) isolated from Lake Zabuye, the Tibetan Plateau, China, was characterized to elucidate its taxonomy. The strain was aerobic, chemo-organotrophic, and grew optimally at 40 6C, pH 9?5–10?0 and 3?4 M NaCl. Cells of strain DS12 T were non-motile cocci and stained Gram-variable. The major polar lipids of strain DS12 T were diphytanyl and phytanyl-sesterterpanyl diether derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester. No glycolipids were detected. Phylogenetic analysis revealed that the strain formed a distinct lineage within the family Halobacteriaceae. The low 16S rRNA gene sequence similarity values to its closest relatives (91?5–92?5 %) and its signature bases both suggest that the strain has no close affinity with any members of the family Halobacteriaceae with validly published names. Therefore, it is proposed that strain DS12 T (=AS 1.3240 T =JCM 11890 T ) represents the type strain of a novel species in a new genus, Halalkalicoccus tibetensis gen. nov., sp. nov. The family Halobacteriaceae was proposed by Gibbons (1974) to incorporate both rods and cocci that required high concentrations [over 12 % (w/v)] of NaCl for growth and included two genera: Halobacterium and Halococcus. Recently, the availability of 16S rRNA gene sequence and polar lipid composition data has resulted in the recognition of taxonomic diversity at the genus level and 18 genera have now been described in this family (Grant et al., 2001; Wainø et al., 2000; Oren et al., 2002; Hezayen et al., 2002; Vreeland et al., 2002). Of these, only three genera contain extremely halophilic coccoid bacteria, i.e. Halococcus, Haloterrigena and Natronococcus. The aim of this study was to describe a novel haloalkaliphilic coccus isolated from Lake Zabuye, Tibet, China. It differs from representatives of known genera of the Halobacteriaceae and, thus, a new genus and species, Halalkalicoccus tibetensis gen. nov., sp. nov., is proposed to accommodate this strain. Lake Zabuye (31u 209 N 84u 059 E) is located in the Tibetan Plateau at 4421 m above sea level. It is an alkaline chloride- sulfate salt lake (pH 9?4, 250 g salt l 21 ). During a broad study of characterization of haloarchaea isolated from Lake Zabuye, strain DS12 T was isolated using a complex medium containing (g l 21 ): Casamino acids (Difco), 7?5; yeast extract (Difco), 10?0; trisodium citrate, 3?0; MgSO 4 .7H 2 O, 1?0; KCl, 10?0; LiCl, 0?1; Fe 2+ and Mn 2+ , trace; NaCl, 200; and Na 2 CO 3 , 10?0. Methods for enrichment and isolation were as described previously (Tindall et al., 1980). Strain DS12 T exhibited non-motile coccoid morphology in both liquid and solid cultures at various growth stages, as determined by phase-contrast microscopy without fixation and by Gram staining with acetic acid fixation (Fig. 1). Cells did not lyse in water like halococcal archaea. Results of physiological and chemotaxonomic analyses are given in the species description and Table 1. The methods Abbreviations: PG, phosphatidylglycerol; PGP-Me, phosphatidylglycerol phosphate methyl ester; PGS, phosphatidylglycerol sulfate. Published online ahead of print on 29 July 2005 as DOI 10.1099/ ijs.0.63916-0. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain DS12 T is AF435112. 63916 G 2005 IUMS Printed in Great Britain 2501 International Journal of Systematic and Evolutionary Microbiology (2005), 55, 2501–2505 DOI 10.1099/ijs.0.63916-0