希瓦氏菌胞外电子传递介导的洛克沙胂生物转化机制研究

As a livestock additive, roxarsone was widely used in poultry industry. However, most roxarsone was ultimately excreted in unmetabolized form with the feces to the environment. Roxarsone can be readily degraded and further transformed into more toxic inorganic arsenic (As). The genus Shewanella with a remarkable ability of extracellular electron transfer were widely spread in subsurface environment. Shewanella was involved in biotransformation of various kinds of environmental pollutants including roxarsone. The aim of this project was to investigate the biotransformation mechanisms of roxarsone mediated by extracellular electron transfer of Shewanella putrefaciens CN32. Based on the complexity and plastic of extracellular electron transfer in S. putrefaciens CN32, it will be firstly probed that biotransformation of roxarsone under various water contamination conditions. Pathways and mechanisms of biotransformation will be predicted and further confirmed using bioinformation technology and molecular experiments. Key enzymes involved in the above transformation process will be identified and characterized as well. With the finishing of this project, more insight into biotransformation of roxarsone will be gained. These results will be meaningful to further control and mitigate water contamination caused by roxarsone.

洛克沙胂(3-硝基-4-羟基苯胂酸)被用作饲料添加剂广泛用于畜禽养殖业。洛克沙胂绝大部分以原始形态随畜禽粪便最终被释放到环境中。环境中的微生物能够降解转化洛克沙胂，释放出毒性更强的无机砷。希瓦氏菌是环境中普遍分布的一种具有胞外电子转移能力的独特细菌，能够实现包括洛克沙胂在内的多种环境污染物的降解转化过程。本项目拟以Shewanella putrefaciens CN32为模式菌株，对其胞外电子传递过程介导的洛克沙胂生物转化机制进行深入研究。首先，基于希瓦氏菌胞外电子传递的复杂性和可塑性，研究洛克沙胂的生物转化过程对不同水质污染因素的响应规律；然后通过实验结果的解析预测可能的转化途径，综合运用生物信息学、分子生物学手段，阐明相应的生物转化机制。同时，对关键蛋白酶的编码基因进行分析与功能表征。通过本项目的研究能够进一步阐明洛克沙胂导致无机砷污染产生的机制，对于污染的进一步调控和去除具有重要意义

希瓦氏菌的胞外电子转移过程在洛克沙胂生物转化中起到重要作用，然而其胞外电子转移过程具有传递网络的复杂性和环境可塑性。本项目围绕可能影响其胞外电子转移的水质污染因素展开研究，结合生物信息学、分子生物学、荧光光谱学等方法，对典型水质污染条件下，洛克沙胂的希瓦氏菌生物转化机制进行了初步研究。研究结果表明，上述生物转化过程表现出硝酸盐代谢途径的独立性，而对以腐殖酸为代表的天然有机质表现出分子量依赖性。不同分子量范围的腐殖酸均能够促进生物转化过程，并且中等分子量（1~3 kDa）范围内的腐殖酸促进作用更大。基于UV-Vis和荧光光谱分析，阐明了腐殖酸富含的苯环和醌基在促进生物转化过程中的重要作用。与此同时，生物转化产物的毒性也相应表现出增强的现象。通过项目的实施，进一步增加了洛克沙胂生物转化可能带来的环境风险和转化机制方面的认识，能够为洛克沙胂引发的砷污染的调控乃至污染去除提供理论依据。