Fig. 4.

Final proportions of β-lactam-resistant E. coli cc11-1 after five transfers in liquid LB broth and biofilms. These are the endpoint data for the experiments described in Fig. 3, which varied dose of ampicillin and initial frequencies of resistant cells: resistant, high and low indicate initial frequencies of 100%, 50%, and 2% cc-11-1 CrimCTXM. Lines indicate fitted linear models and data points represent independent replicates. Antibiotic dose had a stronger impact on the final frequency of resistance in broth than in biofilm grown cells (growth mode*dose interaction P < 0.0001).