Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Department of Earth Science, University of Southern California, Los Angeles, California 90007, United States.
Environ Sci Technol. 2021 Jul 20;55(14):10142-10151. doi: 10.1021/acs.est.1c00356. Epub 2021 Jul 1.
Direct interspecies electron transfer (DIET) between microbial species prevails in some key microbial consortia. However, the electron transfer mechanism(s) in these consortia is controversial due to lack of efficient characterization methods. Here, we provide an in situ anaerobic spectroelectrochemical coculture cell (in situ ASCC) to induce the formation of DIET coculture biofilm on the interdigitated microelectrode arrays and characterize the electron transfer directly. Two typical DIET cocultures, and wild-type (G.m&G.s) and and a strain deficient in citrate synthase (G.m&G.s-Δ), were selected. In situ Raman and electrochemical Fourier transform infrared (FTIR) spectroscopy indicated that cytochromes are abundant in the electric syntrophic coculture. Cyclic voltammetry and potential step experiment revealed a diffusion-controlled electron transfer process and the electrochemical gating measurements further demonstrated a cytochrome-mediated electron transfer in the DIET coculture. Furthermore, the G.m&G.s-Δ coculture displayed a higher redox conductivity than the G.m&G.s coculture, consistent with the existence of an intimate and efficient electrical connection between these two species. Our findings provide the first report of a redox-gradient-driven electron transport facilitated by c-type cytochromes in DIET coculture, supporting the model that DIET is mediated by cytochromes and suggest a platform to explore the other DIET consortia.
种间直接电子转移 (DIET) 在一些关键的微生物共生体中普遍存在。然而，由于缺乏有效的表征方法，这些共生体中的电子转移机制仍存在争议。在这里，我们提供了一种原位厌氧光谱电化学共培养细胞（in situ ASCC），以诱导 DIET 共培养生物膜在叉指微电极阵列上形成，并直接对电子转移进行表征。选择了两种典型的 DIET 共培养物， 和野生型 （G.m 和 G.s） 和 以及柠檬酸合酶缺陷的 菌株（G.m 和 G.s-Δ）。原位拉曼和电化学傅里叶变换红外（FTIR）光谱表明，细胞色素在电共生共培养物中丰富。循环伏安法和电位阶跃实验表明存在扩散控制的电子转移过程，电化学门控测量进一步证明了 DIET 共培养物中细胞色素介导的电子转移。此外，G.m 和 G.s-Δ 共培养物的氧化还原电导率高于 G.m 和 G.s 共培养物，这与这两种物质之间存在密切有效的电连接一致。我们的研究结果首次报道了 DIET 共培养物中 c 型细胞色素介导的氧化还原梯度驱动的电子传递，支持了 DIET 由细胞色素介导的模型，并为探索其他 DIET 共生体提供了一个平台。
