Abstract：
Geobacter sulfurreducens DL1 is a metal-reducing dissimilatory bacterium frequently used to produce electricity in bioelectrochemical systems (BES). The biofilm formed on electrodes is one of the most important factors for efficient electron transfer; this is possible due to the production of type IV pili and c-type cytochromes that allow it to carry out extracellular electron transfer (EET) to final acceptors. In this study, we analyzed the biofilm formed on different support materials (glass, hematite (Fe2O3) on glass, fluorine-doped tin oxide (FTO) semiconductor glass, Fe2O3 on FTO, graphite, and stainless steel) by G. sulfurreducens DL1 (WT) and GSU1771-deficient strain mutant (Δgsu1771). GSU1771 is a transcriptional regulator that controls the expression of several genes involved in electron transfer. Different approaches and experimental tests were carried out with the biofilms grown on the different support materials including structure analysis by confocal laser scanning microscopy (CLSM), characterization of electrochemical activity, and quantification of relative gene expression by RT-qPCR. The gene expression of selected genes involved in EET was analyzed, observing an overexpression of pgcA, omcS, omcM, and omcF from Δgsu1771 biofilms compared to those from WT, also the overexpression of the epsH gene, which is involved in exopolysaccharide synthesis. Although we observed that for the Δgsu1771 mutant strain, the associated redox processes are similar to the WT strain, and more current is produced, we think that this could be associated with a higher relative expression of certain genes involved in EET and in the production of exopolysaccharides despite the chemical environment where the biofilm develops. This study supports that G. sulfurreducens is capable of adapting to the electrochemical environment where it grows.
摘要：
硫化焦耳杆菌DL1是一种金属还原异化细菌，通常用于在生物电化学系统（BES）中产生电能。电极上形成的生物膜是有效电子转移的最重要因素之一；这是可能的，因为IV型菌毛和c型细胞色素的产生使其能够进行细胞外电子转移（EET）到最终受体。在这项研究中,我们分析了在不同支撑材料(玻璃，赤铁矿（Fe2O3）在玻璃上，掺氟氧化锡(FTO)半导体玻璃,Fe2O3对FTO，石墨,和不锈钢）通过G.硫还原DL1（WT）和GSU1771缺陷型菌株突变体（Δgsu1771）。GSU1771是转录调节因子,其控制参与电子转移的若干基因的表达。用生长在不同支撑材料上的生物膜进行了不同的方法和实验测试，包括通过共聚焦激光扫描显微镜（CLSM）进行结构分析，电化学活性的表征，并通过RT-qPCR定量相对基因表达。分析了参与EET的所选基因的基因表达，观察到pgcA的过度表达，omcS,omcM,和来自Δgsu1771生物膜的omcF与来自WT的omcF相比，epsH基因的过度表达，参与胞外多糖合成。尽管我们观察到对于Δgsu1771突变株，相关的氧化还原过程与WT菌株相似，产生更多的电流，我们认为，这可能与EET和胞外多糖生产中涉及的某些基因的较高相对表达有关，尽管生物膜发展的化学环境。这项研究支持G.硫还原能够适应其生长的电化学环境。
