膜污染是膜生物反应器技术发展的重要限制因素，生物膜形成是膜污染发生的主要形式。细菌的成膜行为受控于其胞内的第二信使分子信号系统，而环二鸟苷酸（c-di-GMP）作为通用第二信使分子在细菌中普遍存在。本项目拟采用环境工程学手段，全面研究细菌胞内c-di-GMP控制细菌胞外多聚物分泌进而影响膜污染发生的关键介导作用，并通过宏基因组、宏转录组学等分子生物学方法从关键基因表达特征及对应细菌类群分布等方面，揭示c-di-GMP影响膜污染形成的微生物学及分子生物学机制。在此基础上，利用一氧化氮(NO)和L-谷氨酸作为外部控制信号分子，构建基于c-di-GMP分子调控的膜污染控制方法。并从关键基因系及相应菌群对NO和L-谷氨酸的响应特征等方面，阐明NO和L-谷氨酸调控c-di-GMP水平进而控制膜污染的分子机制。研究成果将为从细菌代谢调控层面认识膜污染的深层次发生机制以及为相应控制方法的开发提供基础。

Membrane fouling is a key factor hindering the wider application of the membrane bioreactor (MBR) technology, in which bacteria attachment and the resultant biofilm formation is a major cause. The biofilm formation behaviors of bacteria are mediated by the second messager signaling system, where bis-(3’-5’)-cyclic dimeric guanosine monophosphate (c-di-GMP) is found as a universal second messager molecule. By using environmental engineering tools combining with modern biomolecular techniques, the aim of this project is to investigate the mediating role of c-di-GMP in the membrane fouling process, and to developed novel membrane fouling control strategies based on external signal molecule regulating of intercellular c-di-GMP levels. The mechanism of c-di-GMP in mediating membrane fouling through the regulation of extracellular polymeric substances (EPS) production will be investigated and uncovered. The key functional diguanylate cyclases (DGCs) and phosphodiesterases (PDEs) genes involved in c-di-GMP level regulation will be identified, with their expression patterns being characterized during the membrane fouling process using metagenomic and metatranscriptomic analysis, to elucidate the metabolic and biomelcular basis of the mediating role of c-di-GMP. Novel membrane control strategies will in turn be developed based on external regulation of the intercellular c-di-GMP levels, using nitric oxide (NO) or L-glutamate as an external regulating signal molecule. The DGCs and PDEs genes and the corresponding bacteria community targeted by NO- or L-glutamate will be identified with their responses to NO or L-glutamate exposure being characterized to reveal the molecular mechanism of NO and L-glutamate in regulating c-di-GMP levels for membrane fouling control. This project is expected to provide new insights in the membrane fouling process from the perspective of bacterial metabolic regulation. And it would inspire and promote new developments in novel membrane fouling control strategies based on c-di-GMP regulation.