Adaptive Evolution of Synthetic Cooperating Communities Improves Growth Performance
(A) Nutrient exchange and dependence in co-culture of two E. coli strains L and K. Strain L is incapable of synthesizing leucine, while strain K is unable to synthesize lysine. In the co-culture, if exchange of leucine and lysine occurs then both strains can grow in glucose minimal medium. Panel (B) shows the concentration profiles of glucose (red x) and optical density (black squares) during batch growth of the co-culture. The error bars indicate the standard deviations across replicates. (C) Genomic DNA from the two mutants were extracted from the co-culture at several time points during batch growth of the co-culture and analyzed by qPCR. Blue circles and red diamonds represent the K and L strains, respectively. The error bars were calculated by the error propagation method described in File S2. (D) The ratio of K to L was calculated from the qPCR results. The K to L ratio measured using qPCR was 1.59±0.18 for a 1∶1 mixture of un-evolved cells based on OD600. The error bars indicate standard deviations.