两株产电菌电子介体介导的胞外电子传递机理研究

构建了Klebsiella oxytoca d7和Shewanella sp.F1 2种纯菌燃料电池,探究了产电菌在产电过程中电子介体传递电子机制.结果表明：K.oxytoca d7只有作产电呼吸时,才会产生电子介体,而Shewanella. sp.F1在好氧呼吸、厌氧呼吸、产电呼吸下均能产生介电体,说明电子介体的产生与产电菌种类有关.两种菌介电体氧化还原电位相当（-250,210mV）,且介于呼吸链NADH和辅酶Q之间.其介电体在胞内呼吸链上截获的电子均源于NADH,说明电子“逸出”位点只取决于介电体本身.K.oxytoca d7在碳源充足和不足时,电子介体产电量分别占总电量的60%和41%;Shewanella. sp.F1分别是57%和50%,说明在碳源充足时,2种菌的产电呼吸都以电子介体机制为主.介电体传递电子过程直接影响了阳极底物的转化和燃料电池的产电性能.

Comparative study of extracellular electron transfer mechanism mediated by electron transfer mediators in two strains of electricigenic bacteria

Microbial fuel cells (MFCs) inoculated pure electricigenic bacteria strain Klebsiella oxytoca d7and Shewanella sp. F1 were constructed respectively, and the mechanisms of electron transfer by the electron transfer mediators (ETMs) during their electricity generation were studied. K. oxytoca d7 could only secrete ETMs during its electricigenic respiration, while the Shewanella sp. F1 could secrete ETMs during either its aerobiotic respiration, anaerobic respiration or electricigenic respiration, which indicated that the generation of ETMs was related to the species of electricigens. The redox potentials of the two species of bacteria were equivalent (-250~210mV), which were between that of the NADH and coenzyme Q in respiratory chain. The electrons intercepted by the ETMs were both denoted from the NADH on the intracellular respiratory chain, indicating that the "escape" site of the electron only depended on the ETMs itself. Under the conditions of sufficient or insufficient carbon sources, in terms of the K. oxytoca d7, the amount of electricity produced by the ETMs accounted for 60% and 41% of the total electricity generated, respectively, while that of the Shewanella sp. F1 was 57% and 50%, respectively. Electricigenic respiration of two electricigens was mainly based on the ETMs mechanism. The conversion of anode substrate and the power generation performance of the MFCs was directly affected by the process of electron transfer mediated by the ETMs.