School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Tokyo, Japan.
Department of Life and Environmental System Science, Graduate School of Nanobiosciences, Yokohama City University, Yokohama, Japan.
Appl Environ Microbiol. 2021 Apr 13;87(9). doi: 10.1128/AEM.00201-21.
In many bacteria, cyclic diguanosine monophosphate (c-di-GMP), synthesized by diguanylate cyclase (DGC), serves as a second messenger involved in the regulation of biofilm formation. Although studies have suggested that c-di-GMP also regulates the formation of electrochemically active biofilms (EABFs) by MR-1, DGCs involved in this process remained to be identified. Here, we report that the SO_1646 gene, hereafter named , is upregulated under medium flow conditions in electrochemical flow cells (EFCs), and its product (DgcS) functions as a major DGC in MR-1. assays demonstrated that purified DgcS catalyzed the synthesis of c-di-GMP from GTP. Comparisons of intracellular c-di-GMP levels in the wild-type strain and a deletion mutant (Δ mutant) showed that production of c-di-GMP was markedly reduced in the Δ mutant when cells were grown in batch cultures and on electrodes in EFCs. Cultivation of the Δ mutant in EFCs also revealed that the loss of DgcS resulted in impaired biofilm formation and decreased current generation. These findings demonstrate that MR-1 uses DgcS to synthesize c-di-GMP under medium flow conditions, thereby activating biofilm formation on electrodes. Bioelectrochemical systems (BESs) have attracted wide attention owing to their utility in sustainable biotechnology processes, such as microbial fuel cells and electrofermentation systems. In BESs, electrochemically active bacteria (EAB) form biofilms on electrode surfaces, thereby serving as effective catalysts for the interconversion between chemical and electric energy. It is therefore important to understand mechanisms for the formation of biofilm by EAB grown on electrodes. Here, we show that a model EAB, MR-1, expresses DgcS as a major DGC, thereby activating the formation of biofilms on electrodes via c-di-GMP-dependent signal transduction cascades. The findings presented herein provide the molecular basis for improving electrochemical interactions between EAB and electrodes in BESs. The results also offer molecular insights into how regulates biofilm formation on solid surfaces in the natural environment.
在许多细菌中，环二鸟苷酸（c-di-GMP）由二鸟苷酸环化酶（DGC）合成，作为一种参与生物膜形成调节的第二信使。尽管研究表明 c-di-GMP 也调节电化学活性生物膜（EABF）的形成，但涉及该过程的 DGC 仍有待鉴定。在这里，我们报告 SO_1646 基因（以下称为 ）在电化学流动池（EFC）中的中等流动条件下上调，其产物（DgcS）作为 MR-1 中的主要 DGC 发挥作用。酶测定表明，纯化的 DgcS 从 GTP 催化 c-di-GMP 的合成。在野生型菌株和 缺失突变体（Δ突变体）中比较细胞内 c-di-GMP 水平表明，当细胞在批量培养和 EFC 中的电极上生长时，Δ突变体中 c-di-GMP 的产生明显减少。在 EFC 中培养 Δ突变体也表明，DgcS 的缺失导致生物膜形成受损和电流产生减少。这些发现表明，MR-1 在中等流动条件下使用 DgcS 合成 c-di-GMP，从而激活电极上的生物膜形成。生物电化学系统（BES）因其在可持续生物技术过程中的应用而受到广泛关注，例如微生物燃料电池和电发酵系统。在 BES 中，电化学活性细菌（EAB）在电极表面形成生物膜，从而作为化学能和电能之间相互转化的有效催化剂。因此，了解在电极上生长的 EAB 形成生物膜的机制非常重要。在这里，我们表明，一种模型 EAB，MR-1，表达 DgcS 作为主要的 DGC，从而通过 c-di-GMP 依赖的信号转导级联激活电极上生物膜的形成。本文的研究结果为提高 BES 中 EAB 与电极之间的电化学相互作用提供了分子基础。研究结果还为 如何调节自然环境中固体表面生物膜的形成提供了分子见解。
