Studies On Polyphasic Taxonomy And Bacteriorhodopsin Encoding Gene Of Halophilic Archaea From Xin-Jiang Region

Halophilic archaea had been isolated from various hypersaline environments. Bacteriorhodopsin (BR) is a retinal-binding membrane protein with seven membrane-spanning segments and functions as a light-driven proton pump in halophilic archaea. And BR protein has great development trend and application value. In this dissertation, we reviewed the development of bacterial taxonomy, the study on halophilic archaea. and the structure, function and application of BR protein. Our research focused on polyphasic taxonomy of the halobacterial strains from Xin-Jiang Region and the analysis on bop gene fragment.Some strains were isolated from the high altitude salt lakes located in no man's land of Altun Mountain in the south of Xin-Jiang, such as Ayakekumu Lake (an altitude of 3884 m), Aularz Lake and Kertun Lake, and the Aibi Lake (an altitude of 188 m) in a low altitude land of northern Xin-Jiang. In accordance with the principle of polyphasic taxonomy, a systematic study had been conducted on the taxonomy of six isolates subsequently. Three novel species, Natrinema altunense sp. nov, Haloterrigena saccharevitans sp. now and Halobiforma salilacus sp .nov, were proposed for type strains AJ2~T, AB14~T and AJ5~T, respectively. This research enriched the taxonomy of halophilic archaea and resolved the taxonomy status of some particular halobacteria from Xin-Jiang. There are eighteen genera including fifth-four species in the class Halobacterlaceae at present. Nine novel species, which were isolated from hypersaline environments in China, however, belong to five genera as following, Natrinema , Natronorubrum, Natrialba, Halobiforma and Halorubrum. The result indicated that the halobacterial strains from China have some terrain traits.On the basis of analysis about bop gene fragment, it was considered that the resource of bop gene from Xin-Jiang formed a microbiological population, which possessed biodiversity and its own trait. This is the first reported detection of bop genes in Natrinema and Halobiforma. The results of genetic analysis and sequence comparison indicated that the bop fragments with high level of genetic divergencewere faced with both purifying selection and bias mutation pressure, and the BR proteins from the isolates are good materials for study on light-driven proton pump. At present the BR proteins were divided into four different kinds according to their sources. Based on the sequence analysis, however, we suggest that BR proteins should be divided into three kinds according to their amino acid sequences. Lateral gene transfer was not detected in our research. Therefore, we amended the Mukohata's assume to explain the evolutional") mode of bop gene.Up to now, most salt lakes located in the south of Xin-Jiang haven't been exploited because of their dreadful environment, pathless position, high altitude and absent oxygen. However, the s:ate could provide original microbial ecological environment for the evolution study and resource utilization. And this is the first study on the three high altitude salt lakes in southern Xin-Jiang.