Reduction Characteristics And Differential Expression Of Acidiphilium Cryptum XTS Cr(Ⅵ)-reduced Related Gene

Abstract:In the past decades, the rapid development of manufacturing industry causes increasingly serious environmental problem which rises people’s attention for environmental management. Heavy metal like chromium Cr（Ⅵ） pollution is one of the most severe water pollution problem. Based on the fact that Acidiphilium cryptum XTS is capable of reducing Cr（Ⅵ） under acidic conditions, it has been utilized in this study to enhance Cr（Ⅵ） reduction in different conditions. To be specific, the effect of pH, initial Cr（Ⅵ） concentration, the existence of Fe（Ⅲ） and oxygen concentration on Cr（Ⅵ） reduction conducted by Acidiphilium cryptum XTS has been investigated and the orthogonal experiment L9（34） has been utilized to find the optimal condition for Cr（Ⅵ） reduction. It has been shown that the optimal condition of Cr（Ⅵ） reduction by Acidiphilium cryptum XTS is at pH2.9under the help of100mg/L ferric ion with initial80mg/L Cr（Ⅵ）. In this condition,67.48%Cr（Ⅵ） has been reduced in24hours.I type cytochrome c encoded by gene Acry₂099is thought to be involved in Cr（Ⅵ） reduction pathway of Acidiphilium cryptum XTS by transferring electrons released from respiratory chain to high oxidation state metal ions like Cr（Ⅵ）. Differential expression of Acry₂099at different conditions has been studied by using quantitative real-time PCR. The result shows that increased expression level of Acry₂099under different initial pH presents a down trend with the increase of pH value; and it presents a first increase then decrease trend under different initial Cr（VI） concentration. In summary, increased expression level of Acry₂099at different conditions correlates with the enhanced behavior of Cr（VI） reduction in different conditions, which suggests Acry₂099may be involved in Cr（VI） reduction pathway.In order to enhance the expression of Acry₂099for the purpose of improving the ability of Cr（VI） reduction by Acidiphilium cryptum XTS, the plasmid for high-level expression of Acry₂099has been constructed. This plasmid aims to be transformed into Acidiphilium cryptum XTS by electroporation or conjugation to acquire the engineering Acidiphilium cryptum XTS strain for efficient Cr（Ⅵ） reduction. Plasmid transformation by electroporation or conjugation is still ongoing.