The process for producing ammonium for agriculture and industry is expensive, but microbes can produce ammonium from nitrogen gas in the atmosphere (called nitrogen fixation). Camil Diaz from the University of Delaware seeks to build a sustainable, nitrogen-fixing co-culture. In a simple community of two microbes, E. coli and A. vinelandii, A. vinelandii produces ammonium that is used by E. coli. This relationship is a one way street, but modifying the E. coli so that it provides glucose to A. vinelandii makes this a mutually beneficial relationship. This metabolite exchange increases the total biomass of the co-culture. Future work will continue to improve this symbiotic relationship.