Institute of Environmental Research at Greater Bay Area; Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou, China.
School of Environmental Science and Engineering, Guangzhou University, Guangzhou, China.
Microbiol Spectr. 2024 Jun 4;12(6):e0381123. doi: 10.1128/spectrum.03811-23. Epub 2024 Apr 22.
In the nitrogen biogeochemical cycle, the reduction of nitrous oxide (NO) to N by NO reductase, which is encoded by gene, is the only biological pathway for NO consumption. In this study, we successfully isolated a strain of denitrifying R-1 from sewage treatment plant sludge. This strain has strong NO reduction capability, and the average NO reduction rate was 5.10 ± 0.11 × 10 µmol·h·cell under anaerobic condition in a defined medium. This reduction was accompanied by the stoichiometric consumption of acetate over time when NO served as the sole electron acceptor and the reduction can yield energy to support microbial growth, suggesting that microbial NO reduction is related to the energy generation process. Genomic analysis showed that the gene cluster encoding NO reductase of R-1 was composed of R, Z, D, F, Y, L, and Z, which was identified as that in other strains in clade I. Respiratory inhibitors test indicated that the pathway of electron transport for NO reduction was different from that of the traditional electron transport chain for aerobic respiration. Cu, silver nanoparticles, O, and acidic conditions can strongly inhibit the reduction, whereas NO or NH can promote it. These findings suggest that modular NO reduction of R-1 is linked to the electron transport and energy conservation, and dissimilatory NO reduction is a form of microbial anaerobic respiration.
Nitrous oxide (NO) is a potent greenhouse gas and contributor to ozone layer destruction, and atmospheric NO has increased steadily over the past century due to human activities. The release of NO from fixed N is almost entirely controlled by microbial NO reductase activities. Here, we investigated the ability to obtain energy for the growth of R-1 by coupling the oxidation of various electron donors to NO reduction. The modular NO reduction process of denitrifying microorganism not only can consume NO produced by itself but also can consume the external NO generated from biological or abiotic pathways under suitable condition, which should be critical for controlling the release of NO from ecosystems into the atmosphere.
在氮生物地球化学循环中，一氧化二氮（NO）通过一氧化二氮还原酶（由基因编码）还原为 N，是唯一的 NO 消耗生物途径。在这项研究中，我们成功地从污水处理厂污泥中分离出一株反硝化 R-1 菌株。该菌株具有很强的 NO 还原能力，在厌氧条件下，在确定的培养基中，NO 作为唯一的电子受体时，其平均 NO 还原率为 5.10 ± 0.11×10 µmol·h·cell-1。随着时间的推移，当 NO 作为唯一的电子受体时，NO 的还原伴随着乙酸盐的化学计量消耗，并且这种还原可以产生能量来支持微生物的生长，这表明微生物的 NO 还原与能量产生过程有关。基因组分析表明，R-1 的编码 NO 还原酶的基因簇由 R、Z、D、F、Y、L 和 Z 组成，这与 I 群中其他菌株的基因簇相同。呼吸抑制剂试验表明，NO 还原的电子传递途径与传统的好氧呼吸电子传递链不同。Cu、银纳米粒子、O 和酸性条件可以强烈抑制还原，而 NO 或 NH 可以促进还原。这些发现表明，R-1 的模块化 NO 还原与电子传递和能量守恒有关，异化型 NO 还原是一种微生物厌氧呼吸形式。
一氧化二氮（NO）是一种强效温室气体，也是破坏臭氧层的元凶，在过去的一个世纪中，由于人类活动，大气中的 NO 含量一直在稳步增加。固定氮释放的 NO 几乎完全由微生物 NO 还原酶活性控制。在这里，我们研究了通过将各种电子供体的氧化与 NO 还原偶联来获得 R-1 生长能量的能力。反硝化微生物的模块化 NO 还原过程不仅可以消耗自身产生的 NO，还可以在合适的条件下消耗生物或非生物途径产生的外部 NO，这对于控制生态系统向大气中释放 NO 应该是至关重要的。
