Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, Ås, Norway.
FEMS Microbiol Ecol. 2013 Mar;83(3):672-84. doi: 10.1111/1574-6941.12024. Epub 2012 Oct 29.
Denitrifying bacteria have variable ability to perform efficient and balanced denitrification during oxygen depletion. NO is often assumed to exert a positive feedback in the transcription of denitrification genes, because NO-dependent activators have been identified. The regulatory network of denitrification is complex, however, and the significance of NO signalling needs to be studied in vivo. We utilized acetylene-catalysed NO oxidation to scavenge NO produced by batch cultures of denitrifying bacteria during transition from oxic to anoxic respiration, to explore the effects on the kinetics of NO, N(2) O and N(2) production. The results demonstrated that nanomolar concentrations of NO accumulating prior to complete depletion of oxygen exert a significant positive feedback on the initiation of denitrification in Paracoccus denitrificans. The early NO signal appeared essential to minimize the transient accumulation of NO during the subsequent anoxic phase for Agrobacterium tumefaciens, but not for P. denitrificans and Pseudomonas aureofaciens. In summary, the results indicate that the early accumulation of nanomolar concentrations of NO has a significant, but strain-dependent effect on the expression of denitrification.
反硝化细菌在缺氧时进行高效和平衡的反硝化作用的能力各不相同。由于已经鉴定出依赖于 NO 的激活剂，因此通常假定 NO 在反硝化基因的转录中发挥正反馈作用。然而，反硝化的调控网络非常复杂，需要在体内研究 NO 信号的意义。我们利用乙炔催化的 NO 氧化来清除反硝化细菌在从好氧呼吸向缺氧呼吸过渡过程中产生的 NO，以探讨其对 NO、N（2）O 和 N（2）产生动力学的影响。结果表明，在氧气完全耗尽之前积累的纳摩尔浓度的 NO 对 Paracoccus denitrificans 反硝化作用的起始具有显著的正反馈作用。对于 Agrobacterium tumefaciens，早期的 NO 信号对于最小化随后缺氧阶段中 NO 的瞬时积累是必不可少的，但对于 P. denitrificans 和 Pseudomonas aureofaciens 则不是。总之，结果表明，纳摩尔浓度的早期 NO 积累对反硝化作用的表达有显著的、但依赖于菌株的影响。
