Zhu Ting-Ting, Cheng Zhou-Hua, Yu Sheng-Song, Li Wen-Wei, Liu Dong-Feng, Yu Han-Qing
CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, 230026, China.
School of Life Sciences, University of Science and Technology of China, Hefei, 230026, China.
Environ Microbiol. 2022 Apr;24(4):1838-1848. doi: 10.1111/1462-2920.15939. Epub 2022 Feb 21.
Exoelectrogenic bacteria (EEB) are capable of anaerobic respiration with diverse extracellular electron acceptors including insoluble minerals, electrodes and flavins, but the detailed electron transfer pathways and reaction mechanisms remain elusive. Here, we discover that CymA, which is usually considered to solely serve as an inner-membrane electron transfer hub in Shewanella oneidensis MR-1 (a model EEB), might also function as a reductase for direct reducing diverse nitroaromatic compounds (e.g. 2,4-dichloronitrobenzene) and azo dyes. Such a process can be accelerated by dosing anthraquinone-2,6-disulfonate. The CymA-based reduction pathways in S. oneidensis MR-1 for different contaminants could be functionally reconstructed and strengthened in Escherichia coli. The direct reduction of lowly polar contaminants by quinol oxidases like CymA homologues might be universal in diverse microbes. This work offers new insights into the pollutant reduction mechanisms of EEB and unveils a new function of CymA to act as a terminal reductase.
产电细菌（EEB）能够利用包括不溶性矿物质、电极和黄素在内的多种细胞外电子受体进行厌氧呼吸，但详细的电子传递途径和反应机制仍不清楚。在此，我们发现，通常被认为仅在模式产电细菌——嗜水气单胞菌MR-1中作为内膜电子传递枢纽的CymA，可能还具有作为还原酶直接还原多种硝基芳香化合物（如2,4-二氯硝基苯）和偶氮染料的功能。通过添加蒽醌-2,6-二磺酸盐可以加速这一过程。嗜水气单胞菌MR-1中基于CymA的不同污染物还原途径可以在大肠杆菌中进行功能重建和强化。像CymA同源物这样的喹啉氧化酶对低极性污染物的直接还原可能在多种微生物中普遍存在。这项工作为产电细菌的污染物还原机制提供了新的见解，并揭示了CymA作为末端还原酶的新功能。
