Dissertation Research: Decoding the dynamics of cryptic microscale biogeochemical cycling in a phototropic consortium

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Microbial metabolism has shaped the global ecosystem since early geological time and, despite the emergence of macroscopic life, remains the engine that drives global cycling of nutrients. In diverse environments, from the deep sea to the human gut, these essential ecosystem processes are mediated not by a single species, but by the interactions of metabolically-interdependent microbial communities. Ecosystem health depends upon these intricate webs of interacting microbes. However, such exchanges are often invisible via traditional approaches, and the chemical transformations involved remain cryptic. This proposal investigates microbial aggregates, the 'pink berries' of the Sippewissett salt marsh, as a model system for understanding how microbial interactions moderate nutrient cycles over spatial scales relevant to microorganisms (nanometers to micrometers). This research will link fluctuations in carbon cycling throughout the day with changes in the micrometer-scale sulfur cycle. This work investigates how the transfer of carbon from sulfide-oxidizing photosynthetic bacteria drives the metabolic activity of nearby sulfate reducing bacteria. An interdisciplinary approach will be used to synthesize information from high-throughput genomics and systems biology with data from high-resolution geochemical analytical techniques. The proposed research will pioneer new ways to elucidate the influence of microbial interactions on material and energy flux within ecosystems that will be broadly applicable across other ecosystems. This work is relevant not only to understanding microbial interactions, but will provide needed benchmarks for modeling of the sulfur cycle in both modern and early earth history. Support for this project will strengthen research collaborations between four major research institutions across the country, and foster educational opportunities from the graduate through K-12 level. All data will be publicly accessible and research findings will be communicated broadly, through public lectures and science blogs.