Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China.
Biotechnol Bioeng. 2012 Nov;109(11):2904-10. doi: 10.1002/bit.24554. Epub 2012 Jun 1.
Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were considered two alternative pathways of dissimilatory nitrate reduction. In this study, we firstly reported that both denitrification and DNRA occurred in Pseudomonas alcaliphila strain MBR with an electrode as the sole electron donor in a double chamber bio-electrochemical system (BES). The initial concentration of nitrate appeared as a factor determining the type of nitrate reduction with electrode as the sole electron donor at the same potential (-500 mV). As the initial concentration of nitrate increased, the fraction of nitrate reduced through denitrification also increased. While nitrite (1.38 ± 0.04 mM) was used as electron acceptor instead of nitrate, the electrons recovery via DNRA and denitrification were 43.06 ± 1.02% and 50.51 ± 1.37%, respectively. The electrochemical activities and surface topography of the working electrode catalyzed by strain MBR were evaluated by cyclic voltammetry and scanning electron microscopy. The results suggested that cells of strain MBR were adhered to the electrode, playing the role of electron transfer media for nitrate and nitrite reduction. Thus, for the first time, the results that DNRA and denitrification occurred simultaneously were confirmed by powering the strain with electricity. The study further expanded the range of metabolic reactions and had potential value for the recognization of dissimilatory nitrate reduction in various ecosystems.
反硝化和异化硝酸盐还原为铵（DNRA）被认为是异化硝酸盐还原的两种替代途径。在本研究中，我们首先报道了在双室生物电化学系统（BES）中，电极作为唯一电子供体时，假单胞菌 MBR 同时发生反硝化和 DNRA。硝酸盐的初始浓度似乎是在相同电位（-500 mV）下，以电极作为唯一电子供体时决定硝酸盐还原类型的因素。随着硝酸盐初始浓度的增加，通过反硝化还原的硝酸盐比例也增加。当亚硝酸盐（1.38±0.04 mM）而不是硝酸盐作为电子受体时，通过 DNRA 和反硝化的电子回收分别为 43.06±1.02%和 50.51±1.37%。通过循环伏安法和扫描电子显微镜评估了由 MBR 菌株催化的工作电极的电化学活性和表面形貌。结果表明，MBR 菌株的细胞附着在电极上，作为硝酸盐和亚硝酸盐还原的电子转移介质发挥作用。因此，首次通过电力为菌株供电，证实了同时发生 DNRA 和反硝化的结果。该研究进一步扩展了代谢反应的范围，对于在各种生态系统中识别异化硝酸盐还原具有潜在价值。
