Unraveling response mechanism of electron transport mechanism to uranium-exposure in Bacillus sp. X02

Abstract

With the development of the uranium mining industry, the remediation of uranium pollution is an urgent environmental problem to be solved. Bioreduction is currently recognized as a U(VI) bioremediation method with good application prospects. However, inadequate reporting of uranium-reducing bacteria and low bioreduction efficiency are the main reasons limiting the application of the bioreduction method. In this paper, we isolated an efficient uranium-reducing bacterium, Bacillus sp. X02, explored the effect of U(VI) on bioreduction efficiency through electron transport mechanisms. The results showed that the maximum removal and reduction rate were 98.35 % and 62.43 %, respectively. Further studies revealed that the efficiency of extracellular electron transport of Bacillus sp. X02 was enhanced under U(VI) exposure. But uranium stress down-regulated the expression of F-type ATPase, Cytochrome c reductase ISP, Cytochrome c oxidase, and Cytochrome bd complex, inhibited the processes of complex III, complex IV, and ATP synthesis in the oxidative phosphorylation electron transport pathway, decreasing the electron transfer and U(VI) reduction capacity of Bacillus sp. X02 ultimately. This work proposed a new electron transfer pathway for U(VI) bioreduction and provided new insights into the effect of uranium on bioreduction efficiency.