Dose-response plot of Y. pestis growth as a function of FR900098 concentration.

Fractional growth is calculated as the ratio of cell density (OD₆₀₀) in the presence of inhibitor to cell density in the absence of inhibitor. Nonlinear regression fitting was performed, resulting in an IC₅₀ of 29 µM (6.4 µg/mL). The goodness-of-fit (R²) value is indicated. For comparison, the IC₅₀ of ampicillin is 10.8 µM (3.8 µg/mL; see Figure S1).