Production and consumption of nitrous oxide in nitrate-ammonifying microorganisms

硝酸盐氨化微生物中一氧化二氮的产生和消耗

• 批准号: 324263958
• 负责人: Professor Dr. Jörg Simon
• 金额: --
• 依托单位: Arbeitsgruppe Microbial Energy Conversion and Biotechnology
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/324263958?language=en
• 关键词: Production; consumption; nitrous; oxide; nitrate

Nitrous oxide (N2O; laughing gas) is an effective atmospheric greenhouse gas and contributes to ozone depletion in the stratosphere. The impact of N2O on climate change makes N2O mitigation an international challenge, in particular in the context of the increasing world population. Anthropogenic N2O emissions are mainly caused by microorganisms from agricultural soils and are favoured by the application of nitrogenous fertilizers. Many different pathways of microbial metabolism have been shown to contribute to N2O generation in diverse habitats and multiple enzymes have been reported to produce N2O. On the other hand, only one type of enzyme (N2O reductase; NosZ) has been described that reduces N2O, yielding N2.Microbial N2O generation from nitrate under anoxic conditions results from denitrification or dissimilatory nitrate reduction to ammonium (DNRA). In denitrifiers, nitrate is reduced to N2 via the intermediates nitrite, nitric oxide (NO) and N2O, although the final step of N2O reduction might be absent or impaired in denitrifying cells. In the DNRA process, N2O appears to be a side product of nitrite and NO detoxification. Some DNRA-performing species contain a NosZ enzyme but their environmental role is currently unresolved. This project aims to characterize the enzymology of production and consumption of N2O in two DNRA model bacteria, namely Wolinella succinogenes and Bacillus vireti. Both organisms have been shown to possess functional nos gene clusters and to couple N2O reduction to cell growth. In W. succinogenes this represents a form of anaerobic respiration that uses N2O as sole electron acceptor. Cells of W. succinogenes and B. vireti are genetically tractable and the construction of deletion mutants has been successfully established in the applicant's laboratory.Using various mutants the project aims to dissect the contribution of individual assimilatory and dissimilatory enzymes to N2O production in W. succinogenes and B. vireti. Furthermore, the potential of the cells to act as N2O sinks will be explored. Since N2O is formed as a product of NO detoxification, the role of candidate NO-reducing enzymes in nitrosative stress defence will also be addressed. Experimentally, the project combines genetic engineering with microbial physiology and biochemistry as well as state-of-the-art determination of gaseous products of nitrate/nitrite reduction in growing bacterial cultures.Taken together, the project seeks to broaden our knowledge on the underexplored role of DNRA organisms in release and consumption of atmospheric N2O. Conceivably, research outcomes will impact on global greenhouse gas mitigation strategies.

一氧化二氮（N2 O;笑气）是一种有效的大气温室气体，并导致平流层臭氧消耗。N2 O对气候变化的影响使N2 O减排成为一项国际挑战，特别是在世界人口不断增加的情况下。人为N2 O排放主要是由农业土壤中的微生物引起的，并受到氮肥施用的影响。许多不同的微生物代谢途径已被证明有助于在不同的生境中产生N2 O，并且已报道多种酶产生N2 O。另一方面，只有一种类型的酶（N2 O还原酶; NosZ）被描述为还原N2 O，产生N2。在缺氧条件下，微生物从硝酸盐产生N2 O是由反硝化或异化硝酸盐还原成铵（DNRA）引起的。在反硝化细胞中，硝酸盐通过中间体亚硝酸盐、一氧化氮（NO）和N2 O还原为N2，尽管N2 O还原的最后一步可能在反硝化细胞中不存在或受损。在DNRA过程中，N2 O似乎是亚硝酸盐和NO解毒的副产物。一些执行DNRA的物种含有NosZ酶，但它们的环境作用目前尚未解决。本项目旨在表征两种DNRA模式细菌，即Wolinella succinogenes和Bacillus vireti中产生和消耗N2 O的酶学。这两种生物体已被证明具有功能性nos基因簇，并将N2 O还原与细胞生长偶联。In W.这代表了一种使用N2 O作为唯一电子受体的厌氧呼吸形式。W.琥珀酸类和B.本项目利用不同的突变体，旨在剖析单个同化和异化酶对W.琥珀酸类和B. vireti。此外，将探讨细胞作为N2 O汇的潜力。由于N2 O是作为NO解毒的产物形成的，因此也将讨论候选NO还原酶在亚硝化应激防御中的作用。在实验上，该项目将基因工程与微生物生理学和生物化学以及最先进的硝酸盐/亚硝酸盐还原气体产物的测定相结合，旨在扩大我们对DNRA生物体在大气N2 O释放和消耗中未被探索的作用的认识。可以想象，研究成果将对全球温室气体减排战略产生影响。