Fig. 4. Fitness of mutant strains grown alone or during coculture with the WT strain and the effects of genome deletions on fitness and antibiotic production.

(A) Fitness [colony-forming unit (CFU)] of mutant strains. (B) Decreases in genome size negatively correlate with fitness (top) and positively correlate with antibiotic production (bottom). (C) Division of labor during coculture of the WT and strain 9H1A at different starting frequencies. Increasing frequencies of 9H1A cause increased antibiotic production (F_2,7 = 107.7, r² = 0.969, P < 0.001) (red) but only negatively affect colony fitness at frequencies >~50% (F_2,7 = 37.95, r² = 0.916, P < 0.001) (black). Quadratic regression lines include the 95% confidence interval.