喹诺酮类抗生素对水体沉积物中汞的生物甲基化影响及作用机制

In recent years, the antibiotics pollution in the water environment was extremely serious so that it becoming a focus of concern and research. The biological methylation of mercury in the sediment of aquatic environment is essential for geochemical circulation and pollution control of mercury, meanwhile, low dosage of antibiotics might stimulate the growth of microorganism, hence the mechanism of antibiotics in sediment effecting biological methylation of mercury become more significant. This study will select five kinds of quinolone antibiotics with different concentration applied to microbiological media culture which contains two kinds of microbial methylation, sulfate reducing bacteria (Desulfovibrio desulfuricans) or iron reducing bacteria (Geobacter sulfurreducens), making out the effects of microbial methylation between quinolones and methylation microorganisms, reveal the mechanism of microbial methylation depending on various doses of quinolones, investigation the physiology activity of microorganisms and the efficiency of mercury methylation were influenced by various doses of quinolones. Simultaneously, by simulating control experiment in microzone of aquatic sediment, A) revealing the migration and transformation of quinolone antibiotics in interphase of aquatic environment; B) investigating the effect of quinolone antibiotics to population of microorganism in sediment; C) analyzing speciation and concentration distribution of mercury in the interphase of overlying water, sediment and pore water; D) expounding mechanism of methylmercuric formation and release in the condition of antibiotics coexisting with mercury in sediment, these provide scientific basis to prevent the combined pollution of antibiotics and mercury.

水体沉积物中汞的生物甲基化对汞的地球化学循环和污染防治至关重要，而低剂量抗生素可能刺激微生物的活性，因此，研究沉积物中抗生素影响汞生物甲基化的意义重大。本研究拟选5种常用喹诺酮类抗生素，通过纯培养研究其对汞甲基化微生物-硫酸盐还原菌(Desulfovibrio desulfuricans )和铁还原菌(Geobacter sulfurreducens ) 的影响，揭示喹诺酮类抗生素对汞甲基化微生物的剂量-效应关系，考察喹诺酮类抗生素对微生物活性和汞甲基化速率的作用机制。此外，通过模拟水体沉积物微域的控制实验，揭示喹诺酮类抗生素在水体各相间的迁移转化规律，考察其对沉积物中微生物种群特征的影响，分析上覆水-沉积物-间隙水各相间汞的赋存形态和分布特征，阐明沉积物中抗生素和汞共存条件下甲基汞的形成与释放机理，为防治水生生态系统的抗生素和汞复合污染提供科学依据。

汞的环境过程与效应，尤其是水体沉积物中汞的生物甲基化，一直是环境科学领域的研究热点之一。新型污染物抗生素的大量排放和在沉积物中的累积可能造成环境甲基汞生成的改变。由于汞甲基化过程的复杂性以及水生态系统的多样性，目前抗生素输入对水体沉积物中汞的甲基化影响机理及主要控制因素仍不明确，针对喹诺酮类抗生素-汞-沉积物的复合体系研究鲜有研究。阐明水体沉积物中汞甲基化微生物对不同浓度水平的喹诺酮类抗生素的应激反应和相应的汞甲基化作用机制，是本研究要解决的关键科学问题。.研究从细胞、生理生化与分子生物学水平上揭示沉积物中汞甲基化的主要贡献者（硫酸盐还原菌和铁还原菌）暴露在喹诺酮类抗生素下的汞甲基化作用机制。研究表明，铁还原菌对汞和抗生素具有较强的耐受能力（>μg/L），并可实现对汞的高效还原和甲基化反应（1-4%）。在抗生素的介入下，菌体的汞甲基化能力有所提升，且提升效应会在抗生素混合时更加明显。在抗生素和汞的长期刺激下，菌体也发生了应激性改变，对应的功能基因gyrA和hgcAB分别提升了210%和44.8%。在模拟水体-沉积物系统中，抗生素介入后，甲基汞/总汞的比例显著提升（300%），说明抗生素胁迫诱导了水生环境甲基汞的释放。.研究表明新兴污染物的排放会改变环境原本的生态系统反应。对汞污染而言，抗生素可使水环境中更多的无机汞偏向甲基汞的生成，改变原有的汞循环，为人类健康造成更严重的潜在威胁。研究结果为抗生素-汞复合污染造成的生态汞循环影响提供了一定的理论依据。