溶解有机物(DOM)的生物地球化学命运在水生态系统中显示出重要的环境意义。然而,目前对DOM与微生物之间的营养关系的理解限制了DOM作为微生物的异养底物或电子穿梭的能力。在这项工作中,我们提供了光电的第一个证据,一种新的营养联系,发生在DOM和非光养微生物之间。具体来说,在反硝化硫杆菌-DOM耦合系统中证明了光电营养反硝化过程,其中DOM充当微生物光敏剂以驱动反硝化硝酸盐还原模型。硝酸盐的还原是假一级反应,动力学常数为0.06±0.003h-1,主要的含氮产物是氮。反硝化基因表达显著上调(p<0.01),包括nar,nir,nor,和不,支持硝酸盐向氮的转化是微生物介导的过程。有趣的是,DOM光敏化引发的光电过程促进了DOM本身的腐殖化,纯DOM辐照几乎相反的趋势。这一发现不仅揭示了DOM在阳光照射的水生态系统中作为微生物光敏剂的作用,而且还提出了一种在地表环境中促进阳光驱动的反硝化的策略。
The biogeochemical fates of dissolved organic matter (DOM) show important environmental significance in aqueous ecosystems. However, the current understanding of the trophic relationship between DOM and microorganisms limits the ability of DOM to serve as a heterotrophic substrate or electron shuttle for microorganisms. In this work, we provide the first evidence of
photoelectrophy, a new trophic linkage, that occurs between DOM and nonphototrophic microorganisms. Specifically, the photoelectrotrophic denitrification process was demonstrated in a Thiobacillus denitrificans-DOM coupled system, in which DOM acted as a microbial photosensitizer to drive the model denitrifier nitrate reduction. The reduction of nitrate followed a pseudo-first-order reaction with a kinetic constant of 0.06 ± 0.003 h-1, and the dominant nitrogenous product was nitrogen. The significant upregulated (p < 0.01) expression of denitrifying genes, including nar, nir, nor, and nos, supported that the conversion of nitrate to nitrogen was the microorganism-mediated process. Interestingly, the photoelectrophic process triggered by DOM photosensitization promotes humification of DOM itself, an almost opposite trend of pure DOM irradiation. The finding not only reveals a so far overlooked role of DOM serving as the microbial photosensitizer in sunlit aqueous ecosystems but also suggests a strategy for promoting sunlight-driven denitrification in surface environments.