Dissertation Research: The influence of resource gradients on soil bacterial communities in a simple ecosystem

现代分子技术大大提高了我们识别细菌的能力。这使得研究控制微生物分布和微生物群落组成的因素成为可能，并解决有关微生物在基本生态过程中所起作用的基本问题。虽然目前的研究有助于认识微生物的地理分布模式，应用成熟的宏观生态学理论可能会提供洞察这些模式的机制。 将在南极洲的麦克默多干旱山谷内研究资源可利用性对土壤细菌群落的影响。该区域包含营养物、水和盐的环境梯度，预计这些环境梯度将强烈影响这些简单的细菌主导的群落。2010年12月，从12个代表苔藓和藻类地上生产自然梯度的地点收集了土壤样本。基于DNA的指纹技术应用于这些样本揭示了细菌群落结构的变化。2012年，将对其中六种土壤进行重新采样，并使用基于DNA和RNA的技术进行测序，以评估资源可用性如何影响细菌群落组成和代谢活动。此外，土壤水分和有机质含量将通过实验操作，以研究它们在构建土壤细菌群落中的相互作用及其对微生物活性的影响。该项目将有助于更好地了解细菌群落结构的机制，以及这反过来如何影响土壤微生物介导的生态系统过程的速率。基于RNA的方法也代表了一种新的方法，用于确定细菌的活性多样性，一种具有潜在价值的技术，用于调查所有土壤中的细菌群落，其中大部分微生物群落可能是不活跃的。 这项研究将通过让本科生参与主要研究，并通过与GK-12外展和目前在弗吉尼亚理工大学开展的南极留学项目的互动，影响更广泛的受众。

Modern molecular techniques have greatly increased our ability to identify bacteria. This has made it possible to investigate what controls the distribution of microbes and the composition of microbial communities, and to address fundamental questions about the roles that microbes play in essential ecological processes. Although current research is contributing to the recognition of geographic distribution patterns of microorganisms, the application of well-developed macroecological theory may provide insight to mechanisms underlying these patterns. The influence of resource availability on soil bacterial communities will be examined within the McMurdo Dry Valleys of Antarctica. This region contains environmental gradients of nutrients, water, and salts which are predicted to strongly influence these simple, bacteria-dominated communities. Soil samples from 12 sites representing a natural gradient in above-ground production by moss and algae were collected in December 2010. DNA-based fingerprinting techniques applied to those samples revealed variation in bacterial community structure. Six of these soils will be resampled in 2012 and sequenced using both DNA- and RNA-based techniques to assess how bacterial community composition and metabolic activity are affected by resource availability. In addition, soil moisture and organic matter content will be experimentally manipulated to examine their interactive effects in structuring soil bacterial communities and their influence on microbial activity. This project will contribute to a greater understanding of mechanisms structuring bacterial communities and how this, in turn, may influence rates of ecosystem processes mediated by soil microorganisms. RNA-based methods also represent a novel approach for determining the active diversity of bacteria, a technique with potential value for investigating bacterial communities in all soils where a large proportion of the microbial community may be inactive. This research will impact a broader audience by engaging undergraduate students in primary research and through interaction with both GK-12 outreach and an Antarctic study abroad programs currently operating at Virginia Tech.