Current bioprocessing efforts primarily employ clonal populations of microbes.  This approach has inherent limitations, such as the ability to combine different types of reactions in a single organism, and the effects of expressing several proteins on metabolic load which affect yield and productivity.  Synthetic bacterial communities have the potential to address these challenges through a division of labor approach and are likely to have an important role in the future of bioprocessing.  Towards this end we are developing tools for engineering synthetic communities containing Gram-positive and Gram-negative bacteria.   We have recently described synthetic communication pathways between Gram-positive Bacillus megaterium and Gram-negative Escherichia coli.   In this work, using tools from our previous system, we promote coexistence of our hosts through commensalism, where one species depends on another for survival.  We started with auxotrophic E. coli strains that are unable to grow in the absence of exogenously added tryptophan or tyrosine.  We engineered these strains to express proteins that produce the missing essential metabolites with the addition of an acyl-homoserine lactone (AHL) quorum-sensing signal molecule.  Both E. coli strains were observed to show AHL-dependent growth in the absence of tryptophan or tyrosine.  We have also shown that these strains are able to grow in the presence of filtered supernatant from AHL-producing B. megaterium cultures.  The tryptophan and tyrosine-based rescue systems show different responses to AHL with respect to lag phase and growth rate. We will also describe the results of co-culture experiments where the engineered E. coli are co-cultured with AHL-producing B. megaterium and our characterization of these new commensal systems.  Additionally, we will discuss our work towards engineering B. megaterium to require E. coli using a similar cell-cell communication-dependent strategy.  These efforts will enable the design and construction of control systems for engineering microbial consortia with targeted community composition.

Coordinated growth of <i>Bacillus megaterium</i> and <i>Escherichia coli</i> via cell-cell communication

247th National Meeting (2014)

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Coordinated growth of Bacillus megaterium and Escherichia coli via cell-cell communication