Relative fitness of mutants MF33-1-1 and PG2^E10 and of transconjugants T5-1 and T5-5 over passages.

The relative fitness (w) of mutants and transconjugants versus their ancestor strain, respectively, PG2 55–5 and 5632G3 was defined by pairwise competition assays (see Materials and methods). P0, P10 and P40 correspond to passages 0, 10 and 40 in the absence of enrofloxacin selection pressure, with P10 and P40 corresponding to approximately 165 and 605 generations respectively. At least three replicates were performed for each assay; the mean value and the standard deviation (SD) are indicated on the graph.