The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, The College of Agricultural and Food Sciences, Zhejiang A & F University, Hangzhou, 311300, China.
School of Environmental & Resource, Zhejiang A & F University, Hangzhou, 311300, China.
J Hazard Mater. 2019 Jun 5;371:295-303. doi: 10.1016/j.jhazmat.2019.03.023. Epub 2019 Mar 6.
Here, the draft genome of simultaneous nitrification-denitrification strain (SND) Klebsiella sp. KSND revealed possible existence of genes involved in N-assimilation and -dissimilation pathways. The change levels of genes under defined N-sources were analyzed by Quantitative Real-Time PCR. It suggested that NH-assimilation via NADP-glutamate dehydrogenase pathway would occur preferentially. NirBD genes were tightly regulated in a lower level, so that nitrite was rapidly consumed for detoxication by denitrification. Three types of nitrate reductase homologues are surprisingly present in KSND, whereas the dominant nitrate reduction for assimilation and denitrification processes mediates by NapA-type nitrate reductase. Nitric oxide reductase homologues FlRd and FlRd-red provide an adequate capacity for NO detoxification. The recombinant hydroxylamine reductase showed high activity in hydroxylamine to generate ammonium, which might contribute to detoxification mechanism in nitrogen cycling. Overall, this study firstly provides valuable insights into the genes expression and enzyme action, which helps understanding the mechanism of SND processes.
这里，同时硝化-反硝化菌株（SND）Klebsiella sp. KSND 的草图基因组揭示了可能存在参与 N 同化和异化途径的基因。通过定量实时 PCR 分析了在定义的 N 源下基因的变化水平。这表明 NADP-谷氨酸脱氢酶途径的 NH 同化将优先发生。NirBD 基因受到严格调控，处于较低水平，因此亚硝酸盐迅速通过反硝化作用消耗以解毒。令人惊讶的是，KSND 中存在三种类型的硝酸盐还原酶同源物，而 NapA 型硝酸盐还原酶介导的同化和反硝化过程中的主要硝酸盐还原。一氧化氮还原酶同源物 FlRd 和 FlRd-red 为 NO 解毒提供了足够的能力。重组羟胺还原酶在羟胺生成铵方面表现出高活性，这可能有助于氮循环的解毒机制。总的来说，这项研究首次提供了对基因表达和酶作用的有价值的见解，有助于理解 SND 过程的机制。
