Figure 3. Community dynamics of bacteriocin producers in an unstractured environment.

Competitions between bacteriocin producers in an unstructured environment were tested (A) empirically and (B) numerically. Both simulations demonstrate that competition between unequal bacteriocinogenic strains (one triggering mild and the other strong bacteriocin expression) resolves in the mild bacteriocinogenic strain always prevailing. (A) We followed the fluorescently labeled ColA over time to illustrate the competition between a pore former (ColA) and a DNase (ColE7) a mild and strong inducers of colicin expression, respectively. ColE7, the producer of a potent colicin, challenged ColA at various initial frequencies and was always outcompeted. At the higher starting frequencies ColA’s fluorescence was halted for a while (6 hr) but then it increased to its maximum. At lower starting frequencies, ColA outcompeted ColE7 at the onset. Data points are the average of three independent measurements. (B) Time evolution is illustrated by the bacteriocin producers strains A (blue line) and B (red line), mild and strong inducers, respectively, while strain B also produces a potent toxin. The strains were simulated to compete at equal initial frequencies and the weak inducer strain A prevailed.