Some novel members of extremely halophilic archaea, strains AJ11, AJ12 and AJ13, were isolated from the Aularz Lake located in the Altun Mountain National Nature Reserve of Xinjiang, Uygur Autonomous Region in China. Partial DNA fragments encoding a bacteriorhodopsin (BR), as well as for 16S rRNA of isolated strains, were amplified by PCR and their DNA sequences were determined subsequently. On the basis of homology and phylogenetic analysis of the 16S rDNA, we thought that the isolated strains forming a microbiological population are the members of the genus Natrinema. The results of genetic analysis, such as GC content, transition/transversion (Ti/Tv) rate ratios and synonymous substitution rates (Ks) indicate that the br fragments, with a high level of genetic divergence, are faced with both purifying selection and bias mutation pressure. The study provides the basis for use of species and BR proteins resources.
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