School of Physics, Soft Condensed Matter & Physics of Living Systems Seminar, Dr. Seppe Kuehn, University of Illinois

Microbes live in complex communities which play a central role in global nutrient cycles. The flow of nutrients around these cycles are defined by, and define, microbial community structure and metabolic function. What are the organizing principles of metabolically functional microbial communities that sustain life on Earth? How have ecological and evolutionary forces given rise to these organizing principles and can we use them to design and control functional microbial consortia? To address this problem we present work interrogating the flow of metabolites through microbial communities in two contexts.

Our first study uses denitrification as a model process whereby bacterial communities convert nitrate to di-nitrogen gas. Using natural isolates, sequencing and metabolite measurements we develop a statistical approach to mapping community level denitrification rates to genomic composition. Remarkably, we show that the gene content of a community can be used to predict the flux of metabolites through the community.

Second, we present new work on self-sustaining closed microbial biospheres — these complex communities sustain themselves indefinitely when provided with only light by cycling nutrients. We present a new technique to quantify carbon cycling in closed ecosystems non-invasively. We show that an algae-bacteria closed ecosystem persistently cycles carbon on the timescale of months. These microbial biospheres provide a powerful new tool for understanding how nutrient fluxes structure microbial communities to permit the persistence of life on Earth.