Wang Lei, Shan Xiaoman, Xu Yanhui, Xi Quan, Jiang Haiming, Li Xia
School of Life Science and Technology, Inner Mongolia University of Science and Technology, Baotou 014010, China.
School of Mining and Coal, Inner Mongolia University of Science and Technology, Baotou 014010, China.
Int J Mol Sci. 2025 Apr 28;26(9):4195. doi: 10.3390/ijms26094195.
Direct interspecies electron transfer (DIET) is a syntrophic metabolism wherein free electrons are directly transferred between microorganisms without the mediation of intermediates such as molecular hydrogen or formate. Previous research has demonstrated that 6Ac is capable of reducing carbon dioxide through DIET. However, the mechanisms underlying electron uptake in 6Ac during DIET remain poorly understood. This study aims to elucidate the electron and proton flux in 6Ac during DIET and to propose a model for electron uptake in this organism, primarily based on the analysis of gene transcript levels, genomic characteristics of 6Ac, and the pathways generating fully reduced ferridoxin (Fd), reduced coenzyme F (FH), coenzyme M (CoM-SH), and coenzyme B (CoB-SH) during DIET. The findings suggest that membrane-bound heterodisulfide reductase (HdrED), FH-dehydrogenase lacking subunit F (Fpo), and cytoplasmic heterodisulfide reductase (HdrABC)-subunit B of F-reducing hydrogenase (FrhB) complex play critical roles in electron uptake in 6Ac during DIET. Specifically, Fpo is responsible for generating Fd with reduced methanophenazine (MPH), driven by a proton motive force, while HdrED facilitates the reduction of heterodisulfide of coenzyme M and coenzyme B (CoM-S-S-CoB) to CoM-SH and CoB-SH using MPH. Additionally, cytoplasmic heterodisulfide reductase HdrABC and subunit B of coenzyme F-hydrogenase complex (HdrABC-FrhB complex) catalyzes the reduction of oxidized coenzyme F (F) to FH, utilizing CoM-SH, CoB-SH, and Fd. This study represents the first genetics-based functional characterization of electron and proton flux in 6Ac during DIET, providing a model for further investigation of electron uptake in species. Furthermore, it deepens our understanding of the mechanisms underlying electron uptake in methanogens during DIET.
直接种间电子转移（DIET）是一种互营代谢，其中自由电子在微生物之间直接转移，无需分子氢或甲酸等中间体的介导。先前的研究表明，6Ac能够通过DIET还原二氧化碳。然而，DIET过程中6Ac摄取电子的潜在机制仍知之甚少。本研究旨在阐明DIET过程中6Ac的电子和质子通量，并提出该生物体摄取电子的模型，主要基于对基因转录水平、6Ac的基因组特征以及DIET过程中产生完全还原的铁氧化还原蛋白（Fd）、还原型辅酶F（FH）、辅酶M（CoM-SH）和辅酶B（CoB-SH）的途径的分析。研究结果表明，膜结合异二硫化物还原酶（HdrED）、缺乏亚基F的FH脱氢酶（Fpo）以及细胞质异二硫化物还原酶（HdrABC）-还原型辅酶F的氢化酶复合物（FrhB）的亚基B在DIET过程中6Ac摄取电子方面起关键作用。具体而言，Fpo负责在质子动力的驱动下，利用还原型甲萘醌（MPH）生成Fd，而HdrED则利用MPH促进辅酶M和辅酶B的异二硫化物（CoM-S-S-CoB）还原为CoM-SH和CoB-SH。此外，细胞质异二硫化物还原酶HdrABC和辅酶F-氢化酶复合物的亚基B（HdrABC-FrhB复合物）利用CoM-SH、CoB-SH和Fd催化氧化型辅酶F（F）还原为FH。本研究首次基于遗传学对DIET过程中6Ac的电子和质子通量进行了功能表征，为进一步研究该物种的电子摄取提供了模型。此外，它加深了我们对DIET过程中产甲烷菌摄取电子的潜在机制的理解。
