Is denitrification by ammonia oxidising bacteria a response to nitrite toxicity?

氨氧化细菌的反硝化作用是对亚硝酸盐毒性的反应吗？

• 批准号: NE/H018107/1
• 负责人: Liz Baggs
• 金额: $ 8.91万
• 依托单位: University of Aberdeen
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH018107%2F1
• 关键词: denitrification; ammonia; oxidising; bacteria; response

Production of nitrous oxide (N2O) is of environmental concern due to its involvement in global warming and destruction of stratospheric ozone. As soils account for ~70% of the atmospheric loading of N2O management strategies are urgently required to lower emissions. Such strategies need to be formulated around our understanding of the regulation of microbial N2O-producing processes in soils. This project will determine the conditions under which ammonia oxidising bacteria (AOB) demonstrate flexibility in function to reduce nitrite (NO2-) to nitrous oxide, thereby contributing to global warming and destruction of stratospheric ozone. Specifically this project will examine whether this flexibility is a response to nitrite toxicity during nitrification thus releasing N2O under aerobic conditions. It will test the hypotheses: (i) the ability of ammonia oxidising bacteria to denitrify is primarily a NO2- toxicity response, rather than a facultative response to maintain respiration under reduced Redox conditions (ii) AOB switch to using NO2- as an oxygen source to maintain function when a threshold concentration of NO2- is sensed, reducing it to N2O, and (iii) in the soil environment, the necessity of AOB to reduce NO2- will depend on coupling of AOB with nitrite oxidising bacteria (NOB). The student will undertake culture experiments to test the response of strains of AOB and NOB to NO2- addition rates in culture and ascertain a threshold concentration for nitrite reduction by AOB, the optimum NH4+:NO2- ratio for maximum N2O production by AOB, and the influence of NOB in regulating the NO2- concentration and AOB N2O production. A stable isotope approach (15N-18O-enrichment of NO2- and N2O) will be adopted to ascertain that NO2- is used by AOB as an oxygen source above the threshold NO2- concentration for denitrification. The potential for NOB to regulate NO2- concentrations and therefore reduction of NO2- by AOB will be examined through reduced expression of the AOB nirK gene, in sterilised (gamma-irradiated) soil inoculated with AOB and NOB strains from objective 1, and in a natural soil community adopting a combination of 15N-isotopomer and real time molecular approaches. This project will provide the student with training in a wide range of analytical techniques, including analysis by gas chromatography and mass spectrometry and microbiological techniques, as well as a wide range of soil physical and chemical analyses. The student will obtain training in molecular techniques, sample preparation and analysis from SCRI.

一氧化二氮（N2 O）的产生是一个环境问题，因为它涉及全球变暖和平流层臭氧的破坏。由于土壤约占大气N2 O负荷的70%，因此迫切需要采取管理战略来降低排放量。这些策略需要围绕我们对土壤中微生物产生N2 O过程的调控的理解来制定。该项目将确定氨氧化细菌（AOB）在将亚硝酸盐（NO2-）还原为一氧化二氮的功能中表现出灵活性的条件，从而有助于全球变暖和平流层臭氧的破坏。具体而言，本项目将研究这种灵活性是否是在硝化过程中对亚硝酸盐毒性的反应，从而在有氧条件下释放N2 O。它将检验以下假设：（i）氨氧化细菌分解的能力主要是NO2-毒性反应，而不是在还原氧化还原条件下维持呼吸的兼性反应（ii）当感测到NO2-的阈值浓度时，AOB切换到使用NO2-作为氧源以维持功能，将其还原为N2 O，以及（iii）在土壤环境中，AOB还原NO2-的必要性将取决于AOB与亚硝酸盐氧化细菌（NOB）的偶联。学生将进行培养实验，以测试AOB和NOB菌株对培养物中NO2-添加速率的反应，并确定AOB还原亚硝酸盐的阈值浓度，AOB最大N2 O生产的最佳NH 4+：NO2-比例，以及NOB在调节NO2-浓度和AOB N2 O生产中的影响。一个稳定的同位素方法（15 N-18 O-富集NO2-和N2 O）将被采用，以确定NO2-被AOB使用作为氧源高于阈值NO2-浓度反硝化。NOB调节NO2-浓度的潜力，从而减少NO2-的AOB将通过减少AOB nirK基因的表达，在消毒（γ-辐照）的土壤接种AOB和NOB菌株的目标1，并在自然土壤群落采用15 N-同位素和真实的时间分子方法的组合进行检查。该项目将为学生提供广泛的分析技术培训，包括气相色谱和质谱分析和微生物学技术，以及广泛的土壤物理和化学分析。学生将从SCRI获得分子技术，样品制备和分析方面的培训。