(56b) Microelectrode Analysis of an Artificial Phototrophic Biofilm Consortia Reveals a Positive Feedback Basis of Syntrophic Interactions

Consortia can be engineered to optimize multiple functions simultaneously providing a robust platform for bioprocesses. Photoautotrophic consortia have the added benefit of using inexpensive sunlight and CO₂ as energy and carbon sources. Naturally occurring phototrophic organisms often couple with heterotrophic counterparts in an ancient and globally distributed ecological partnership based on syntrophic exchange of mass and energy via chemical species. This naturally occurring ecological template has been reconstructed using an artificial binary community comprised of photoautotrophic Synechococcus and heterotrophic Escherichia coli. Both Synecochoccus and E. coli are industrially relevant microbial strains often engineered for commercial products such as biofuels, bioplastics, amino acids and organic acids. Coculturing permits a mutually beneficial metabolite exchange between the strains; Synechococcus photosynthates support E. coli growth while E. coli consumption of potentially inhibitory organic acids and photosynthetically derived O₂ increases Synecochoccus biomass productivity.  Cocultured Synechococcus biomass productivity was 50% higher than monocultures.  A detailed micron-scale spatial analysis of oxygen gradients within the binary biofilms provided a basis for estimating photosynthetic rates in monocultures and cocultures. The binary system exhibited decreased local oxygen concentration with respect to position. This result corresponds with increased rates of respiration and reduced product inhibition of Synechococcus with respects to O₂ and photorespiration byproducts.  This artificial binary biofilm culture represents a novel and adaptable microbial catalyst platform which exploits renewable carbon and energy inputs.