| Acidithiobacillus ferrooxidans (abbreviation:A.f) is chemautotrophy, which is one of the bioleaching bacteria that is most applied and researched in mineral engineering. A.f strain is used broadly in uranium ore bioleaching as well. But, in bioleaching system, there are many disadvantageous environment factors to affect leaching bacteria. for example, the low pH value enviroment of bioleaching uranium ore, the accumulation of uranium and fluorine ions will produce deleterious influence to bacteria. Mostly uranium ore in China contains high fluorine content. Many literatures have reported the potential inhibitory effects of fluorine on animals. However, available information about the effect of fluorine toxicity on bioleaching microorganisms was very little. It was found that fluorine have strongly bad effect to A.f strain. As for the machanism of fluorine inhibit A.f strain is not clear so far. And it was infered that HF is the real substance to militate, just because HF membrane permeability ranged from10-4to10-3cm/s, five to seven orders of magnitude higher than F-and H+. There are little research to investigate the machanism of fluorine by means of molecular-biological ap-proaches, so this is also an new breakthrough point. The thesis main works include three parts1、The chemical mechanism of fluorine effect to A.f strainA.f strian was inoculated into9K medium containing fluorine, which inspect and verify the perceptible inhibition. A.f strian almost can’t grow when the concentration of fluorine is up to20mg/L. Then a relatively tolerant strain A.f was got by gradual domestication, which can endure40mg/L fluorine. By comparison the effect of each fluorine concentration at different pH values, and integration into the chemical analysis of solution, it is presumed that HF inhibit A.f strain metabolism in bioleaching system.2、The change of F-concentration in A.f strain cellThe intracellular fluorine concentration at different stages of A.f strain treated by proteinase K or not were determined by fluoride ion-selective electrode. It was found that there was a slight decrease without proteinase K treatment. In contrast, after proteinase K treatment, there was an uptrend.When A.f strain treated by proteinase K was inoculated again into9K medium without fluorine and with40mg/L fluorine, respectively, A.f strain still can grow normly in the former but not in the latter. So it is infered that the tolerance of A.f strain to fluorine by domestication maybe was related to cell membrane proteins.3、Comparative Proteomics analysis of A.f strain that growing in normal and containing fluorine circumstancesBy two-dimensional electrophoresis and MALDI-TOF-TOF MS, we identified and analysed the proteomics expression of A.f strain that growing in normal and containing fluorine circumstances. By Imagemaster professional analysis software and Mascot search database, we successfully identified9kinds of differential-expressed proteins.4spots of them are upregulated and5spots are downregulated in the circumstances of fluorine. The differential-expressed proteins related to protein synthesis include:Elongation factors Tu and Ts、Chaperonin Gro EL. The antioxidant protein include:antioxidant, AhpC/Tsa family. The protein related to disulfide bond formation include:Pyridine nucleotide-disulfide oxidoreductase. The protein partecipated in glycometabolism include:Fructose-1,6-bisphosphatase, Ribulose bisphosphate carboxylase, large subunit1and2, ATP synthase subunit beta. So we deduce that protein synthesis and glycometaolism may take part in the resistance to fluorine. |
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