FIG. 5.

Ampicillin degradation rate in planktonic cultures. Kp1 (●) cultures that contained ∼10⁹ CFU/ml degraded ampicillin at a rate statistically different from zero (a). The top series in panel a illustrates the degradation of ampicillin with an initial concentration of 5,000 μg/ml. Least-squares linear regression estimated a degradation rate of 0.63 h⁻¹ with a correlation coefficient (R²) of 0.967. The bottom series in panel a depicts degradation of ampicillin with an initial concentration of 1,000 μg/ml. Linear least-squares regression predicted a degradation rate of 0.83 h⁻¹ with a correlation coefficient (R²) of 0.922. The two rates were averaged to provide an estimated ampicillin degradation rate of 0.73 h⁻¹ for Kp1. The ampicillin degradation rates for Kp102M cultures (○) and the sterile control (▿) were not statistically different from zero (b).