Even allocation of benefits stabilizes microbial community engaged in metabolic division of labor

Metabolic division of labor (MDOL) is commonly observed in microbial communities, where a metabolic pathway is sequentially implemented by several members similar to an assembly line. Uncovering the assembly rules of the community engaged in MDOL is crucial for understanding its ecological contribution, as well as for engineering high-performance microbial communities. To investigate the assembly of the community engaged in MDOL, we combined mathematical modelling with experimentations using synthetic microbial consortia. We built a theoretical framework predict the assembly of MDOL system, and derived a simple rule: to maintain co-existence of the MDOL members, the populations responsible for former steps should hold a growth advantage (m) over the private benefit (n) of the population responsible for last step, and the steady-state frequency of the last population is determined by the quotient of n and m. Our experiments further indicated that our theoretical framework accurately predicted the stability and assembly of our engineered synthetic consortia that degrade naphthalene through two-step or multi-step MDOL. Our results demonstrate that the assembly of microbial community engaged in MDOL is determined by a limited number of parameters. This quantitative understanding provides novel insights on designing and managing stable microbial systems to address grand challenges facing human society in agriculture, degradation of the environment, and human health.