Dissertation Research: Linking N cycling bacterial community composition and function along a mycorrhizal gradient

论文研究：沿着菌根梯度将氮循环细菌群落组成和功能联系起来

• 批准号: 1701972
• 负责人: Adrien Finzi
• 金额: $ 1.88万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-05-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1701972&HistoricalAwards=false
• 关键词: Dissertation; Research; Linking; cycling; bacterial

Soil bacteria play a central role in the cycling of nitrogen (N) in all ecosystems, where plant productivity is often limited by the availability of N. Certain types of bacteria are able to capture N from the atmosphere and make it available for plants through the process of N-fixation. Other bacterial groups use their metabolism to return N to the atmosphere. Plant roots and fungi in soil can influence bacteria, but the effect of these interactions on N cycling is unclear. The aims of this project are to (1) characterize relationships between N-cycle reactions and different groups of bacteria, and (2) to explore how these relationships are influenced by plant roots and fungi. Understanding how factors in soil control N-availability for plants is important for agriculture and forestry. This Doctoral Dissertation Improvement Grant project will enhance the graduate student's dissertation research, provide opportunities for undergraduate students to develop field and laboratory techniques in biogeochemistry, and will be integrated in outreach activities organized through the Boston University Biogeoscience program. Plant roots and mycorrhizal fungi can influence the form and availability of inorganic N in soil, potentially impacting the composition and activity of N-cycling bacterial functional groups. This research will test three hypotheses: (1) enhanced competition for N between plants and soil microbes in forest stands dominated by ectomycorrhizal (ECM) fungi relative to stands dominated by arbuscular mycorrhizal (AM) fungi will select for N-fixers and select against nitrifiers and denitrifiers; (2) high plant demand for inorganic N in rhizosphere soils relative to bulk soils will select for diazotrophs and select against nitrifiers and denitrifiers; and (3) the magnitude of the rhizosphere effect will increase as ECM abundance increases. To test these hypotheses, the abundance of gene copies (DNA) and gene transcripts (RNA) associated with N-fixers, nitrifiers, and denitrifiers will be quantified in rhizosphere soil samples across a mycorrhizal gradient established at the Harvard Forest LTER site in Petersham, MA. Stable isotope approaches will be used to measure rates of N-fixation, nitrification and denitrification. These paired analyses will elucidate relationships between microbial community composition and function and identify how these relationships vary based on biotic interactions between N-cycling bacteria, mycorrhizal fungi and plant roots.

土壤细菌在所有生态系统的氮（N）循环中起着核心作用，在所有生态系统中，植物生产力通常受到N的可用性的限制。其他细菌组利用其新陈代谢将N返回到大气中。 土壤中的植物根和真菌会影响细菌，但是这些相互作用对N循环的影响尚不清楚。该项目的目的是（1）表征N周期反应与不同细菌组之间的关系，以及（2）探讨这些关系如何受植物根和真菌的影响。了解土壤控制植物的N-可用性的因素对于农业和林业很重要。这项博士学位论文改善赠款项目将增强研究生的论文研究，为本科生提供开发生物地球化学现场和实验室技术的机会，并将集成在通过波士顿大学生物学家计划组织的外展活动中。植物根和菌根真菌会影响土壤中无机N的形式和可用性，从而有可能影响N循环细菌官能团的组成和活性。这项研究将检验三个假设：（1）森林中植物和土壤微生物之间N的n竞争增强了由外生菌血体（ECM）真菌主导的，相对于由弧菌菌根菌根（AM）真菌占主导地位的林木，将为N型固定器和nItrifiers和Denitrifiers和Denitrifiers选择； （2）相对于散装土壤，根际土壤中对无机N的植物需求量很高，将选择重18zotrophs，并针对硝化剂和硝化剂选择； （3）随着ECM丰度的增加，根际效应的大小将增加。为了检验这些假设，将在马萨诸塞州Petersham的Harvard Forest lter lter地点建立的基因拷贝（DNA）和基因转录（RNA）（RNA）（RNA）（RNA）（RNA）（RNA）（RNA）。稳定的同位素方法将用于测量N固定，硝化和反硝化的速率。这些配对的分析将阐明微生物群落组成和功能之间的关系，并确定这些关系如何根据N循环细菌，菌根真菌和植物根之间的生物相互作用而变化。