Quantifying the effects of the division of labor in metabolic pathways

• We investigate the division of labor (metabolic function) in microbial systems.
• We compare a syntrophic consortia to a monoculture with equivalent metabolic capability.
• Consortia biomass is always lower than a monoculture with the same metabolic dynamics.
• Increasing the growth rate or substrate affinity does not explain the observed consortial advantage.
• Increased metabolic pathway efficiency (yield) provides the observed increase in productivity.

Division of labor is commonly observed in nature. There are several theories that suggest diversification in a microbial community may enhance stability and robustness, decrease concentration of inhibitory intermediates, and increase efficiency. Theoretical studies to date have focused on proving when the stable co-existence of multiple strains occurs, but have not investigated the productivity or biomass production of these systems when compared to a single ‘super microbe’ which has the same metabolic capacity. In this work we prove that if there is no change in the growth kinetics or yield of the metabolic pathways when the metabolism is specialized into two separate microbes, the biomass (and productivity) of a binary consortia system is always less than that of the equivalent monoculture. Using a specific example of Escherichia coli growing on a glucose substrate, we find that increasing the growth rates or substrate affinities of the pathways is not sufficient to explain the experimentally observed productivity increase in a community. An increase in pathway efficiency (yield) in specialized organisms provides the best explanation of the observed increase in productivity.