Uwe Sauer, Ph.D.

PriME Project: Metabolic Interactions During Marine Polymer Breakdown

Bacterial degradation of polysaccharides in the ocean plays a major role in the cycling of elements at the global scale. While polysaccharides are typically broken down by specialized degraders, microbial communities that assemble around these polysaccharides are comprised of many metabolically diverse, non-specialized consumers. This highlights the role of metabolic cross-feeding, whereby metabolic activity of specialized degraders releases metabolites that fuel the growth of non-specialized consumers. Research by Uwe Sauer’s group focuses on understanding how metabolic cross-feeding structures the assembly of polysaccharide degrading communities, with a particular focus on chitin, which is the most abundant biological polymer in the ocean. Their primary tool is high throughput metabolomics, in combination with other molecular techniques, to reconstruct these metabolic cross-feeding networks in model polysaccharide communities. They have established a model community seeded with marine bacteria, isolated from natural polysaccharide-degrading communities and have established a potential cross-feeding network from produced and consumed metabolites in single species experiments. They unraveled a hierarchical cross-feeding structure, whereby specialized chitin degraders can direct the trajectory of community assembly by secreting enzymes that select for less specialized consumers and influence the metabolites they secrete into a shared resource pool. The group is continuing to use this model system to understand how metabolites shape the assembly of polysaccharide communities. This includes applying bottom-up approaches to reconstruct microbial communities that degrade chitin, applying metabolomics techniques to identify and quantify different classes of compounds that mediate metabolic cross-feeding, and identifying how extracellular enzymes mediate nutrient exchange. With these approaches, they aim to provide a quantitative understanding of how metabolic cross-feeding influences population dynamics and community assembly.

Bio:

Uwe Sauer is a trained microbiologist, having also completed postdoctoral training in metabolic engineering. His research as a principal investigator and, since 2006, as a professor for systems biology at the ETH Zürich, focused on fundamental questions related to microbial metabolism. His lab combines modeling with quantitative experimentation, including mass spectrometry-based methods for 13C-flux analysis and high-throughput metabolomics. His main focus presently is on understanding how microbes coordinate their metabolic operation on short- and long-time scales as well as unraveling metabolic interaction between microbes that sustain and define microbiota. For this project his lab focuses on metabolic interactions between marine species during breakdown of chitin and complex polymers from phytoplankton and identifies mechanisms and rules that underlie sequential colonization. Sauer’s lab brings expertise in microbial interactions, metabolism and metabolic modeling, and his metabolomics lab will provide technological support for several of the subprojects.