FIG 1.

(A) Growth kinetics of Ery^r and Ery^s strains. The experiment was repeated three times. O.D., optical density. (B) Growth competition assay of Ery^r and Ery^s strains in a mixed culture. The Ery^r/Ery^s ratio was initially adjusted to approximately 1:1. At every passage, an aliquot of cultured broth was diluted and spread on a Mueller-Hinton agar plate with and without 16 μg/ml erythromycin. The number of colonies was counted to estimate the ratio of Ery^s and Ery^r strains. The experiment was repeated four times.