整合宏基因组及宏转录组技术探索强化氢基质生物膜反应器重铬酸盐、硒酸盐降解能力研究

Chromate and selenate are highly toxic to humans, thus, are strictly regulated inorganic compounds in the drinking water standards recommended by the WHO. Unfortunately, due to various anthropogenic activities, these two compounds have become common groundwater contaminants all over the world. In China, the general public is concerned with the increasing poisoning cases caused by either direct consuming or in contact with chromate and selenate contaminated water sources. Innovative remediation techniques have been developing to remove these toxic compounds from contaminated groundwater and to mitigate their impacts on human health. Among these new techniques, hydrogen-based membrane biofilm reactor (MBfR) seemed to be more effective in reducing chromate and selenate to their respective harmless forms, a process mediated by some hydrogen-using microorganisms. However, the process can be severely affected many environmental parameters, among which nitrate concentration has been reported to be an essential one. Nitrate is another common groundwater contaminant which is often present at much higher concentrates in groundwater compared with chromate and selenate. And nitrate is a preferable electron acceptor by numerous anaerobic microorganisms that use hydrogen as an electron donor. These reasons prevent MBfR technique from being effectively used to remediate groundwater with nitrate, chromate and selenate present at same time. This proposed research is sought to enhance chromate and selenate removal efficiency with nitrate existing as an electron competitor at higher concentration. Different from previous attempts by other researchers, this study is focused on better understanding of the microorganisms that are involved in hydrogen-based chromate and selenate reduction processes by using metagenomics and metatranscriptomics. Chromate and selenate reducing mechanisms and their relations to nitrate-reducing mechanisms, as well as any unique physiological properties of these microorganisms will be revealed by the advanced molecular microbiology techniques. The results will provide insightful knowledge on how to further engineering the MBfR process to provide optimum growth conditions for the chromate- and selenate-reducing microorganisms to overcome nitrate inhibition.

高危毒性的重铬酸盐及硒酸盐已影响着人类健康与环境安全，对我国地下水具有突出潜在威胁。地下水治理新兴技术氢基质生物膜反应器（MBfR）利用氢气作为电子供体去除重铬酸盐及硒酸盐时，地下水常见的硝酸盐因其电子竞争优势及高浓度而优先获得电子及降解，进而抑制重铬酸盐、硒酸盐的去除。该抑制过程属于细菌对能量供给的自然选择，加大电子供量等方法无法改变细菌对电子受体选择的优先顺序，重铬酸盐、硒酸盐的降解始终处于被抑制的状态。因此，本项目以“硝酸盐的电子竞争优势及其浓度条件而导致重铬酸盐、硒酸盐降解受抑制”为问题切入，通过整合新型分子生物学手段“宏基因组”及“宏转录组”技术揭示重铬酸盐、硒酸盐降解还原菌及其基因多样性，深入剖析重铬酸盐、硒酸盐降解，从而通过微生物调控缩短重铬酸盐、硒酸盐降解过程，为氢自养还原菌降解过程实现“减负”，并最终强化MBfR重铬酸盐、硒酸盐的降解能力。

高危毒性的重铬酸盐及硒酸盐已影响着人类健康与环境安全，对我国地下水具有突出潜在威胁。地下水治理新兴技术氢基质生物膜反应器（MBfR）利用氢气作为电子供体去除重铬酸盐及硒酸盐时，地下水常见的硝酸盐因其电子竞争优势及高浓度而优先获得电子及降解，进而抑制重铬酸盐、硒酸盐的去除。该抑制过程属于细菌对能量供给的自然选择，加大电子供量等方法无法改变细菌对电子受体选择的优先顺序，重铬酸盐、硒酸盐的降解始终处于被抑制的状态。本项目通过整合新型分子生物学手段技术揭示重铬酸盐、硒酸盐降解还原菌及其基因多样性，深入剖析重铬酸盐、硒酸盐降解，从而通过微生物调控缩短重铬酸盐、硒酸盐降解过程，为氢自养还原菌降解过程实现“减负”，并最终强化MBfR重铬酸盐、硒酸盐的降解能力。本项目的主要研究成果为“优化氢基质生物膜反应器材质结构，提高该技术在实际处理受污染地下水的可行性”、“探索了MBfR反应器从常规活性污泥接种并去除地下水中Cr(VI)、Se(VI)的启动与驯化方法”、“优化生物膜氢自养还原菌的遗传物质的提取方法”、“建立适用于MBfR生物膜的微生物种群结构分析技术”、“分析Cr(VI)、Se(VI)在MBfR反应器生物膜中的分布情况”、“剖析出MBfR去除Cr(VI)、Se(VI)过程中生物膜的氮元素循环路径”、“剖析出MBfR去除Cr(VI)、Se(VI)过程中生物膜的碳元素循环路径”以及“解析基于Fe2+浓度调控微生物强化氢基质生物膜反应器Cr(VI)和Se(VI)”。本项目科学意义为建立一套适用于MBfR生物膜的微生物种群结构分析技术，并且重点解析MBfR去除Cr(VI)、Se(VI)过程中生物膜的氮元素循环路径和碳元素循环路径，两个路径有效帮助科研工作者了解Cr(VI)与Se(VI)在降解过程中相关酶作用与循环情况，以利于本项目提出基于Fe2+浓度调控微生物强化氢基质生物膜反应器Cr(VI)和Se(VI)的应用手段。本项目优化氢基质生物膜反应器材质结构，提高该技术在实际处理受污染地下水的可行性，也进一步有利于该技术在基础研究的应用和开展。