Figure 2.
Cooperation improves growth and is quantified by the cooperation level. (A) The mean growth of strain B is presented for sets of co-cultures binned by the measured growth of strain A. The growth of strain B initially increases with that of A as B reaps the invested benefits of cross-feeding. B declines for high A as an excess of cooperation allows A to dominate the available carrying capacity. (B) Cooperation levels, derived from the growth data by equations (1) show characteristic relationships with growth. A always benefits from increases in B's cooperation level, CB, whereas A's own cooperation, CA, is optimal for A at an intermediate level. Error bars are 95% bootstrap confidence intervals.