Dimensions: Taxonomic, genetic and functional biodiversity of above-ground bacterial endophytes in subalpine conifers

氮(N)对地球上的所有生命都是必不可少的，但只有选定的微生物才能将N还原或‘固定’成植物可以利用的形式。通常，植物只有在被生活在土壤中的微生物固定或通过与豆类的共生关系固定时，才能利用大气中的氮，但最近的发现表明，松针内的细菌也可以执行这一关键功能。在这项研究中，加州大学默塞德分校的研究人员将研究细菌和松树(松树)之间的共生关系。目标是了解松针中存在的细菌的多样性，计算有多少N微生物固定以及在什么条件下，并推断固定的N是如何转移到树上的。这项研究可以显著提高我们对氮素循环的理解，并有助于确定针叶林中目前未知的固定氮素来源。更全面地了解氮素循环也将有助于改进气候模型，更好地描述能够固定氮素的微生物可能会导致作物发展的进步。这项研究将培养本科生。现场和实验室技术方面的研究生和博士后研究人员。此外，这项研究将包括与K-8 STEM学校的教师、行政人员和学生进行接触，以服务于代表性不足的群体，并将开发符合共同核心教育标准的探究式学习模块，将其纳入K-8 STEM课程。调查人员将研究亚高山树木内生植物的系统发育多样性和遗传潜力如何影响西部针叶林的固氮。他们的中心假设是，在广阔的地理范围内，软木松树拥有广泛的分类、遗传和功能生物多样性，其中包括互惠固氮的内生菌，由当地环境塑造，部分与邻近的树木共享。为了验证这一点，研究人员将检查石松林内生植物的生物多样性和石油松范围内的共生物种，确定构成多样性格局的因素，并确定分类多样性和固氮之间的关系。测序和基因组分析中的尖端方法将与现有的、高度敏感的原位检测和可视化固氮活动的方法相结合，以了解环境如何塑造内生菌多样性，以及如何塑造亚高山森林的氮循环。

Nitrogen (N) is essential to all life on Earth, but only select microbes can reduce or 'fix' N to a form that plants can use. Typically, plants can only use atmospheric N can when fixed by microbes that live in the soil or via a symbiotic relationship with legumes, but recent findings indicate that bacteria inside pine needles can also perform this critical function. In this research, investigators at University of California, Merced will examine the symbiosis between bacteria and limber pine (Pinus flexilis). The goals are to understand the diversity of bacteria present in pine needles, calculate how much N microbes fix and under what conditions, and infer how this fixed N is transferred to the tree. The research could significantly improve our understanding of the N cycle and help identify a currently unknown source of fixed N within coniferous forests. A more complete understanding of the N cycle will also help improve climate models, and a better characterization of the microbes that can fix Nitrogen could lead to advances in crop development. This research will train undergraduates. graduate students and post-doctoral researchers in both field and lab techniques. Additionally, the research will include outreach to teachers, administrators and students at a K-8 STEM school serving under-represented groups, and will develop inquiry-based learning modules in line with Common Core educational standards for incorporation within the K-8 STEM curriculum.The investigators will examine how the phylogenetic diversity and genetic potential of subalpine tree endophytes affect N fixation within western coniferous forests. Their central hypothesis is that across its broad geographic range, limber pine hosts a broad taxonomic, genetic and functional biodiversity of mutualistic N fixing endophytes, shaped by the local environment, and shared, in part, with neighboring trees. To test this, investigators will examine the biodiversity of endophytes in limber pine and co-occurring species across the limber pine range, identify the factors that structure the patterns of diversity, and determine the relationship between taxonomic diversity and N fixation. Cutting-edge methods in sequencing and genome analysis will be integrated with established and highly sensitive methods for detecting and visualizing N fixing activity in situ to understand how endophyte diversity is shaped by the environment and shapes the N cycle in subalpine forests.