Extracellular electron transfer (EET) is essential in improving the power generation performance of electrochemically active bacteria (EAB) in microbial fuel cells (MFCs). Currently, the EET mechanisms of dissimilatory metal-reducing (DMR) model bacteria Shewanella oneidensis and Geobacter sulfurreducens have been thoroughly studied. Klebsiella has also been proved to be an EAB capable of EET, but the EET mechanism has not been perfected. This study investigated the effects of biofilm transfer and electron mediators transfer on Klebsiella quasipneumoniae sp. 203 electricity generation performance in MFCs. Herein, we covered the anode of MFC with a layer of microfiltration membrane to block the effect of the biofilm mechanism, and then explore the EET of the electron mediator mechanism of K. quasipneumoniae sp. 203 and electricity generation performance. In the absence of short-range electron transfer, we found that K. quasipneumoniae sp. 203 can still produce a certain power generation performance, and coated-MFC reached 40.26 mW/m2 at a current density of 770.9 mA/m2, whereas the uncoated-MFC reached 90.69 mW/m2 at a current density of 1224.49 mA/m2. The difference in the electricity generation performance between coated-MFC and uncoated-MFC was probably due to the microfiltration membrane covered in anode, which inhibited the growth of EAB on the anode. Therefore, we speculated that K. quasipneumoniae sp. 203 can also perform EET through the biofilm mechanism. The protein content, the integrity of biofilm and the biofilm activity all proved that the difference in the electricity generation performance between coated-MFC and uncoated-MFC was due to the extremely little biomass of the anode biofilm. To further verify the effect of electron mediators on electricity generation performance of MFCs, 10 µM 2,6-DTBBQ, 2,6-DTBHQ and DHNA were added to coated-MFC and uncoated-MFC. Combining the time–voltage curve and CV curve, we found that 2,6-DTBBQ and 2,6-DTBHQ had high electrocatalytic activity toward the redox reaction of K. quasipneumoniae sp. 203-inoculated MFCs. It was also speculated that K. quasipneumoniae sp. 203 produced 2,6-DTBHQ and 2,6-DTBBQ. To the best of our knowledge, the three modes of EET did not exist separately. K. quasipneumoniae sp.203 will adopt the corresponding electron transfer mode or multiple ways to realize EET according to the living environment to improve electricity generation performance.

中文翻译：

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生物膜转移和电子介体转移对准肺炎克雷伯菌的影响。 203 MFC的发电性能


细胞外电子转移（EET）对于提高微生物燃料电池（MFC）中电化学活性细菌（EAB）的发电性能至关重要。目前，异化金属还原（DMR）模型细菌希瓦氏菌（Shewanella oneidensis）和硫还原地杆菌（Geobactersulfurreducens）的EET机制已得到深入研究。克雷伯氏菌也被证明是一种能够进行EET的EAB，但EET机制尚未完善。本研究调查了生物膜转移和电子介体转移对准肺炎克雷伯菌的影响。 203 MFC 的发电性能。在此，我们通过在MFC的阳极覆盖一层微滤膜来阻断生物膜机制的影响，进而探究准肺炎克雷伯菌电子介体机制的EET。 203、发电性能。在没有短程电子转移的情况下，我们发现K. quasipneumoniae sp。 203仍能产生一定的发电性能，涂层MFC在770.9 mA/m2电流密度下达到40.26 mW/m2，而无涂层MFC在电流密度1224.49 mA/m2下达到90.69 mW/m2。涂层MFC和未涂层MFC之间发电性能的差异可能是由于阳极覆盖有微滤膜，抑制了阳极上EAB的生长。因此，我们推测K. quasipneumoniae sp。 203还可以通过生物膜机制进行EET。蛋白质含量、生物膜完整性和生物膜活性均证明涂层MFC与未涂层MFC发电性能的差异是由于阳极生物膜生物量极少造成的。 为了进一步验证电子介体对MFC发电性能的影响，在涂层MFC和未涂层MFC中添加10 µM 2,6-DTBBQ、2,6-DTBHQ和DHNA。结合时间-电压曲线和CV曲线，我们发现2,6-DTBBQ和2,6-DTBHQ对准肺炎克雷伯菌的氧化还原反应具有较高的电催化活性。接种203的MFC。还推测K. quasipneumoniae sp。 203产生2,6-DTBHQ和2,6-DTBBQ。据我们所知，EET 的三种模式并不是单独存在的。 K. quasipneumoniae sp.203会根据生存环境采用相应的电子转移方式或多种方式实现EET，以提高发电性能。