Biocathodic electrode-driven denitrification has been proved experimentally in complex biofilms. However, experimentation with isolated bacteria in pure culture is still limited. In this paper, six Alphaproteobacteria (Rhizobiales), found to be dominant in a denitrifying biocathode, have been characterized bioelectrochemically. Bacteria were isolated using strict autotrophic conditions in the presence of nitrate or nitrite. Six representative isolates were selected and proven able to denitrify under autotrophic and heterotrophic conditions in liquid media. Bioelectrochemical reduction of nitrate, nitrite and nitrous oxide was tested using cyclic voltammetry. Electrode-driven nitrite reduction was only detected in four of the six isolates. However, no electrode-driven nitrate or nitrous oxide reduction could be detected for any of them. In the presence of nitrite, estimated midpoint potentials for bioelectrocatalyzed reactions ranged from −500 to −534 mV vs. SHE. Two of the isolates exhibited midpoint potentials at −450 and −486 mV vs. SHE when incubated in the absence of any external nitrogenous electron acceptor. These redox peaks were attributed to electrode-driven hydrogen production in the biofilm. We have proven that electrode-driven nitrite reduction is feasible in monospecific biofilms. However, significant variability in relation to electrode-driven nitrogen reduction processes was observed in closely related species, confirming a strain-specific behavior.

生物阴极电极驱动的反硝化作用已在复杂的生物膜中得到了实验证明。然而，在纯培养物中分离细菌的实验仍然是有限的。在本文中，六α-变形菌（根瘤菌目被发现在反硝化生物阴极中占主导地位的）已通过生物电化学方法进行了表征。在硝酸盐或亚硝酸盐存在下，使用严格的自养条件分离细菌。选择了六个代表性分离株，并证明它们能够在液体培养基中的自养和异养条件下进行反硝化作用。使用循环伏安法测试了硝酸盐，亚硝酸盐和一氧化二氮的生物电化学还原。仅在六个分离物中的四个中检测到电极驱动的亚硝酸盐还原。但是，对于其中任何一个，都无法检测到电极驱动的硝酸盐或一氧化二氮的还原。在亚硝酸盐的存在下，生物电催化反应的估计中点电位相对于SHE为-500至-534 mV 。其中两个分离物在-450和-486 mV处显示中点电势在没有任何外部含氮电子受体的情况下孵育时，与SHE相比。这些氧化还原峰归因于生物膜中电极驱动的氢产生。我们已经证明，电极驱动的亚硝酸盐还原在单特异性生物膜中是可行的。然而，在密切相关的物种中观察到与电极驱动的氮还原过程相关的显着变化，证实了应变特异性行为。