Bacterial Biodiversity Of Microbial Mat In Zabuye Salt, Tibet And Its Impacts On Saline Deposits

Microorganisms in extreme environments, especially the environments with high salinity, had unique physiological, metabolic types, phylogenetic types, and also prolific genetic resources. These extremophiles could be employed as scientific community excellent materials for better understanding the essence of life, the limit of life, the origination and evolution of life, and for exploring extraterritorial life. They also provided rich resources for the development of industrial biotechnology.Bacterial diversity in Zabuye salt lake was investigated by culture-independent approaches and culture methods. Total DNA was extracted from sediments sample of Zabuye salt lake, Tibet. The 16S rRNA gene was amplified by PCR with Bacterial primer f530/r1492. Then the plasmid library of 16S rRNA genes was constructed. The positive clones were screened on plates with IPTG/X-gal/Ap methods. Amplified ribosomal DNA restriction analysis (ARDRA) was carried out with restriction enzymes HaeⅢ, HhaⅠ. Some clones were selected to be sequenced according to the ARDRA patterns and phylogenetic tree was constructed. The phylogenetic tree showed that some clones (57.14% of total clones) belonged to 23 genera inγ-proteobacteria,-proteobacteria,δ-proteobacteria, bacteroidetes, firmicutes, and verrucomicrobia. The rest clones were quite different and were most related with uncultured sequences, forming special division in the tree.Then,24 strains were isolated and enriched and some of them were selected for further research. According Gram staining methods, six selected strains belonged to Gram positive rod and sphere bacteria with thick cell wall and stronger resistance to extreme environments. Randomly selected 12 strains appeared rod-shaped and sphere-shaped with scanning electron microscope.14 strains were chose for 16S rRNA identification. The results showed that these 14 strains belonged to Firmicutes, Betaproteobacteria, and Gammaproteobacteria, with a high similarity to the present species in GenBank. Results comparison of culture methods and culture-independent approaches showed that the isolated strains only accounted for a small part of environmental species. Most parts of species in Zabuye salt lake kept to be developed.The interaction of halophiles from Zabuye salt lake and lithium was studied by absorption test, scanning electron microscope observation and infrared spectroscopy analysis. According to the best initiating volume of bacteria test, the best initiating amount of lithium test, the best starting pH value test and the impact test of potassium, we knew that the best initiating volume of bacteria was 50mL after incubated over night, the initiating amount of lithium was 652ng/mL, the optium starting pH was 7.5. The results showed that the average absorption was 2.8121μg/g dry weight, ranging 0.7228-9.2156μg/g dry weight, containing two excellent strains Halobacillus sp. zby1,9.2165μg/g dry weight and Halobacillus sp. zby5, 3.3707μg/g dry weight. After scanning electron microscope and infrared spectroscopy analysis, it was found that the surface of strains and the surface groups did appear different degrees of changes. It was inferred that selected halophilic strains did have some positive effect in the enrichment, aggregation, deposition process of lithium carbonate; however, this type of effect may be only in biological background level rather than induced process.