Closed microbial communities self-organize to persistently cycle carbon

Abstract

Nutrient cycling is an emergent property of ecosystems at all scales, from microbial communities to the entire biosphere. Understanding how nutrient cycles emerge from the collective metabolism of ecosystems is a challenging problem. Here we use closed microbial ecosystems (CES), hermetically sealed consortia that sustain nutrient cycles when provided with only light, to learn how microbial communities cycle carbon. A new technique for quantifying carbon exchange shows that CES comprised of an alga and diverse bacteria self-organize to robustly cycle carbon. Comparing a library of CES, we find that carbon cycling does not depend strongly on the taxonomy of the bacteria present. Metabolic profiling reveals functional redundancy across CES: despite strong taxonomic differences, self-organized CES exhibit a conserved set of metabolic capabilities. SummaryClosed microbial communities of algae and bacteria self-organize to robustly cycle carbon via emergent metabolite exchange.