Fe0/Fe2+-Dependent Nitrate Reduction in Anammox Consortia Questions the Enzymatic Mechanism of Nitrate Reduction by Anammox Bacteria,ACS Sustainable Chemistry & Engineering

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Fe0/Fe2+-Dependent Nitrate Reduction in Anammox Consortia Questions the Enzymatic Mechanism of Nitrate Reduction by Anammox Bacteria
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2020-09-21 , DOI: 10.1021/acssuschemeng.0c05152
Zhen Bi _{1,

2} , Wenjing Zhang ₁ , Min Ni ₁ , Ge Song ₁ , Yong Huang _{1,

2}

Affiliation

The anammox bacteria (AnAOB) have been suggested to perform dissimilatory Fe⁰/Fe²⁺-dependent nitrate reduction to ammonium (DNRA), with nitrite as intermediate. However, evidence at genetic and transcriptional levels for how AnAOB reduces nitrate is still lacking, making their roles in this process obscure and questionable. The short-term batch assays and long-term operation of bioreactor combined with 16S rDNA sequencing and transcription analysis were used for the first time to investigate the nitrate reduction pathway in anammox consortia. It is shown that AnAOB metabolically well grew with nitrate as the sole nitrogen source. They reduced nitrate to nitrite with highly expressed narG gene. However, the DNRA-enabling gene nrfA was not expressed by AnAOB. Abiotic reduction by Fe⁰/Fe²⁺ contributed to the nitrate and nitrite reduction to ammonium. The correlation analysis of microbial community structure and metabolic functions indicated that amino acid and carbohydrate transport and metabolism interactions in coexisting bacteria could facilitate the AnAOB growth with nitrate as the only nitrogen source. Our findings suggest that the contribution of enzymatic DNRA by AnAOB to the observed nitrate reduction has been probably overestimated in previous publications, and it should be questioned until the clear enzymatic mechanism responsible for nitrate reduction is identified.

中文翻译：

厌氧菌团中Fe ⁰ / Fe ²⁺依赖性硝酸盐还原对厌氧菌还原硝酸盐的酶机制提出了质疑

有人建议以亚硝酸盐为中间体，将厌氧氨氧化细菌（AnAOB）进行异化的Fe ⁰ / Fe ²⁺依赖性硝酸盐还原为铵盐（DNRA）。但是，仍然缺乏在遗传和转录水平上有关AnAOB如何减少硝酸盐的证据，这使得它们在这一过程中的作用难以理解。首次使用了短期反应和生物反应器的长期操作，结合16S rDNA测序和转录分析，来研究厌氧氨氧化菌团中的硝酸盐还原途径。结果表明，以硝酸盐为唯一氮源的AnAOB代谢良好。他们利用高度表达的narG基因将硝酸盐还原为亚硝酸盐。但是，启用DNRA的基因nrfA没有由AnAOB表达。Fe ⁰ / Fe ^2+的非生物还原有助于将硝酸盐和亚硝酸盐还原为铵。微生物群落结构和代谢功能的相关性分析表明，共存细菌中氨基酸和碳水化合物的运输和代谢相互作用可以促进AnAOB以硝酸盐为唯一氮源的生长。我们的发现表明，在以前的出版物中可能高估了AnAOB酶DNRA对观察到的硝酸盐还原的贡献，在确定明确的负责硝酸盐还原的酶机制之前，应该对此提出质疑。

更新日期：2020-10-12

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