希瓦氏菌对环境污染物类胞外电子受体的趋化响应机制研究

Shewanellae species are known for their broad range of terminal electron acceptors and their ability to grow in a wide range of environments.The exceptional reducing ability of Shewanellae depends on its flexible respiratory pathways and extracellular electron transfer capability. The ability of Shewanella species to migrate in response to spatial gradients of electron acceptors may provide a competitive advantage, allowing Shewanellae to move into more favorable environments that increase its chances of survival and growth. The goal of this study is to use the tools available in molecular microbiology and chemistry to determine how Shewanellae bacteria respond to environmental stimuli. Specific interest is placed on identifying the key components of chemotactic signal transduction pathways required for responses to electron acceptors and carbon/energy sources. The results generated from this research can provide information for predicting the behavior of microbial cells in the subsurface during exposure to a variety of environmental stimuli, including electron acceptors, carbon sources, and pollutants. Understanding of the molecular mechanisms behind the chemotaxis will prove beneficial for optimal design of bioremediation strategies.

微生物在环境修复过程中起着重要的作用，而其中希瓦氏细菌由于其强大的还原能力扮演着非常重要的角色，这主要依赖于其灵活的呼吸途径和胞外电子传递能力。希瓦氏菌对环境污染物和胞外电子受体的趋化是其执行功能的基础。本项目拟以研究希瓦氏菌对环境污染物的趋化现象为主要目的，利用多种分析手段探索趋化现象背后的机制，即确定是化学趋化，还是能量趋化或是二者兼而有之，鉴定希瓦氏菌细胞内能够感应趋化物质的关键甲基趋化受体蛋白，深入解析趋化信号转换为细胞内的其它化学信号继续传递以调节细菌鞭毛运动过程中的信号转导机制，进而阐明希瓦氏菌趋化现象背后的分子机理，建立从基因表达水平人工调控以提高希瓦氏菌还原能力的方法，为其应用于环境修复提供理论依据。

希瓦氏菌对环境污染物和胞外电子受体的趋化是其执行功能的基础。它可以使细菌定位于最适宜的生态环境。细菌趋化性在污染物的生物修复过程中发挥着重要作用。然而，希瓦氏菌对于胞外电子受体趋化响应的具体机制仍未得到解析。针对以上科学问题，本项目首次发现希瓦氏菌对于大部分胞外电子受体具有趋化性现象，且希瓦氏菌对于污染物的趋化能力与其对污染物的代谢密切相关；阐明了趋化现象背后的分子机制，即代谢介导的能量趋化机制；希瓦氏菌对于胞外电子受体的趋化响应行为由多种而非单一甲基受体蛋白介导；我们还发现传统的胞内趋化信号转导路径在希瓦氏菌中广泛存在，并证实其中组氨酸激酶及鞭毛介导的运动能力在胞外电子受体的趋化的过程发挥极其关键的作用；最后我们通过合成生物学手段强化希瓦氏菌趋化能力以及胞外电子传递能力从而大大提升希瓦氏菌对于污染物的降解能力；在环境领域最有影响力的刊物Environmental Science & Technology（4篇）、 Environmental Science & Technology Letters （1篇）、Environment International（1篇）上共发表了12篇文章，协助课题组培养了2名研究生。