Survival curves of E. coli with pBG66 plasmid encoding TEM-1 β-lactamase mutants. A. Colony forming units (cfu) on agar plates containing increasing concentrations of ampicillin for E. coli containing R244A, M182T, L201P single and double mutants. B. Cfu for E. coli containing L76N, M182T, L201P single and double mutants. C. Cfu for E. coli containing I47Y:E48C, M182T, L201P mutant combinations. D. Cfu for E. coli containing H158S:V159S:T160H, M182T, L201P mutant combinations. E. Cfu for E. coli containing M69I, M182T, L201P single and double mutants.