c-di-GMP结合转录因子调控希瓦氏菌呼吸作用的分子机制解析

The biological significance and regulatory mechanism of the coexistence of aerobic and anaerobic respiration in bacteria are mostly unknown. Shewanella species are the suitable model to investigate into this phenomenon for their versatile respiration and ability to thrive in the oxic-anoxic interface. c-di-GMP is a bacterial second messenger which regulates bacterial physiology responding to diverse environmental signals. However, its role in regulating bacterial respiration is barely reported. Our previous study reported the DosD, a diguanylate cyclase under regulation of oxygen, and recent results demonstrate that it affects the transcription of many genes involved in aerobic and anaerobic respiration. The DosD-responsive transcription factor (DrtF) has been identified and its binding to c-di-GMP has been characterized preliminarily. This project is aimed to further explore the role of DrtF on respiration and underlying mechanism, that is, to answer or reveal 1) how c-di-GMP regulates the transcription activity of DrtF; 2) how oxygen affects respiration mediated by DrtF. The project will not only deepens our understanding about Shewanella respiration and the coexistence of aerobic and anaerobic respiration in bacteria, but broadens our knowledge on the role of c-di-GMP in bacterial respiration.

细菌有氧和厌氧呼吸共存的生物学意义和调控机制尚不清楚。希瓦氏菌喜居于“有氧-厌氧”交界环境且呼吸作用灵活，是研究呼吸的理想模型。细菌二级信使c-di-GMP可转导多种环境信号以调控细菌生理，但在呼吸调控中的作用尚鲜有报道。我们已报道了希瓦氏菌直接感应氧气的c-di-GMP合成酶DosD。目前更发现 DosD调控很多有氧和厌氧呼吸相关基因的表达，并鉴定了其下游的c-di-GMP结合转录因子DrtF。本项目旨在初步阐明DrtF介导O2/c-di-GMP信号，调控呼吸过程中部分基因表达的分子机制：①确定c-di-GMP调控DrtF转录因子活性的分子调控机理；②认识不同氧气条件下，DrtF在DosD下游的调控单元及在呼吸调控中的作用；本项目将加深对氧气调控希瓦氏菌呼吸作用的机理性认识，为后续的研究奠定基础，最终有助于理解有氧和厌氧呼吸共存的现象，而且将拓展对c-di-GMP生物学功能及调控机制的认识。

希瓦氏菌喜居于“有氧-厌氧”交界环境且呼吸作用灵活，是研究细菌呼吸作用的理想模型。细菌二级信使c-di-GMP可转导多种环境信号以调控细菌生理，但在呼吸调控中的作用尚鲜有报道。本项目在前期研究的基础上，以代表性基因为例，解析了c-di-GMP如何调控FlrA的DNA结合活性，并最终调控BpfA操纵子表达的分子机制。进一步，完整解析了Shewanella putrefaciens CN32利用氧气激活的c-di-GMP合成酶DosD, 将环境氧气信号传递至细胞内；通过细胞内的c-di-GMP结合转录因子FlrA, 调控下游一系列靶基因表达，从而响应氧气环境的信号感应、传递和调控通路和生理作用。而同源比对分析显示，FlrA蛋白及其结合位点在Shewanella属中高度保守，暗示FlrA是该菌属响应氧气调控自身生理的重要转录因子。本项目的研究初步揭示了Shewanella属对氧气的响应机制。作为一种潜在的保守调控机制，该机制可能在Shewanella属的适应和选择宜居环境的进化过程中发挥重要作用。