Dissertation research: Does long-term drought alter the response of microbial communities to moisture?

近几十年来，分子生物学的进步揭示了土壤中微生物的巨大多样性。这些微生物依靠水分来调节细胞内的水分平衡并获取食物。预计美国西部地区的干旱将会增加，可能会给这些生物带来更频繁的水资源压力。其他生物，如植物，对干旱的敏感性不同，这导致群落的组成在干旱时发生变化，有时对水的反应不同。尽管微生物在养分循环中发挥着重要作用，并预测了更恶劣的气候，但我们对这些群落在干旱或其他干扰下可能发生的变化知之甚少。该项目将研究这些土壤微生物群落在干旱下如何变化，以及这些新的耐旱群落对水分的反应是否与非干旱群落不同。为了回答这个问题，将从科罗拉多草原的长期干旱操作中收集土壤，并在实验室中将非干旱和干旱土壤置于一系列湿度水平下。为了描述社区的变化，我们将使用两种令人兴奋的新技术。首先，将土壤中活跃的微生物分离出来。由于微生物能够像种子一样在休眠状态下存活很长一段时间，因此将活跃生长的微生物——那些影响生态系统功能的微生物——与休眠的微生物分开是很重要的。其次，高通量测序和精细分辨率的样本分类将用于报告整个群落的变化，以及哪些物种对干旱更敏感或更不敏感。这项研究将阐明土壤微生物群落如何在干燥气候下发生变化，这可能如何影响这些群落控制的营养循环，以及与植物和动物相比，微生物群落如何对干扰做出反应并从干扰中恢复。这些发现将完善群落如何应对干扰的一般生态原则，并提高我们预测不同气候条件下可能发生的变化和反馈的能力。

Molecular advances in recent decades have revealed the immense diversity of microorganisms that inhabit the soil. These microorganisms depend on moisture to regulate the water balance in their cells and access food. Drought is expected to increase in areas of the US West, likely causing more frequent water stress for these organisms. Other organisms, like plants, differ in their sensitivity to drought, and this causes the composition of the community to shift under drought, sometimes to one that responds differently to water. Despite the important role of microorganisms in the cycling of nutrients, and predictions of harsher climates, we know little about how these communities might change under drought or other disturbances. This project will study how these soil microbial communities will change under drought, and whether these new drought-tolerant communities respond differently to moisture than non-drought communities. To answer this question, soils will be collected from a long-term drought manipulation in a Colorado grassland and subject both non-drought and drought soils to a range of moisture levels in the lab. To describe how the community changed, two exciting new technologies will be used. First, microorganisms that are active in the soil will be isolated. Since microorganisms are able to survive in a dormant state for long periods of time, much like seeds, it is important to separate the actively growing microorganisms - those that are affecting the function of the ecosystem - from those that are dormant. Second, high-throughput sequencing and sample taxonomy at a fine resolution will be used to report whole-community changes as well as which species in particular might be more or less sensitive to drought.This research will elucidate how soil microbial communities might shift under drier climates, how this might influence nutrient cycles these communities control, and also how microbial communities, compared to plants and animals, respond to and recover from disturbance. The findings will both refine general ecological principles of how communities respond to disturbance, and improve our ability to predict changes and feedbacks that might occur under different climate regimes.