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

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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.