Engineering Emergent Properties in Synthetic Microbial Communities

Traditionally, engineers and synthetic biologists exert control over microbial metabolism by adding or removing genes and pathways from a single host. However, new paradigms have been realized though the ‘consortia’ concept of engineering and compartmenting metabolic function within assigned community members. Beneficial emergent properties, such as enhanced productivity and/or stability, can be engineered into synthetic or thoughtfully constructed microbial communities. This presentation focuses on how emergent properties have been realized from community-engineering. Binary consortia were either metabolically engineered (via genome reduction) or naturally prone to cooperate in a ‘producer-consumer’ motif.  These systems ranged from synthetic Escherichia coli co-cultures engineered for mutualistic exchange-detoxification of acetic acid to artificial wild-type assemblies of phototrophic cyanobacteria and heterotrophic counter parts. These distinct binary cultures demonstrated enhanced biomass productivity and resistance to metabolite feed-back inhibition. For example, the effect of oxygen availability on metabolically engineered E. coli systems was found to be a controlling factor for acetic acid exchange and subsequent phenotype-specific spatial patterning in biofilms and biomass productivity in chemostats. Similarly, oxygen gradients were imposed on a constructed consortium consisting of wild-type photoautotroph (Thermosynechococcus elongatus) and chemoheterotroph (Meiothermus ruber), which responded with an increased resistance to the growth inhibition effect of high oxygen-tension. This research lends critical insight to a grand-challenge for biological engineers and synthetic biologists aiming to capitalize on knowledge gained from model systems and phenomenological observation to rationally design microbial communities for controllable outputs.