(328e) Design and Construction of a Synthetic, Tunable Microbial Consortium

Microbial symbiosis confers many advantages to its participants and has the potential to extend beyond naturally occurring systems. Applications for this kind of synthetic system include microbial production of molecules that are difficult to synthesize or may take many different steps and/or reactions to produce, such as biofuels or pharmaceuticals. Here we attempt to create a tunable microbial symbiotic system by genetically engineering E. coli auxotrophs to cross-feed and support each other when grown in co-culture. Synthetic metabolic circuits were designed to allow tunable control of the system via the export of essential amino acids by each of the auxotrophs. In our system, a tyrosine auxotroph (Δtyr) produces tryptophan for the tryptophan auxotroph (Δtrp) and vice versa. Inducible promoters are used to control the expression of relevant target genes, which then control the amino acid synthesis and export. It has been previously shown that the growth rate and composition of such a co-culture are determined by the export rate and cellular requirement of essential molecules. By adding specific amounts of inducers, we have been able to produce a gradient of target gene expression and a co-culture with variable growth rate and composition.