FIG 3.

Growth inhibition by different concentrations of acetate and different pH levels. Experiments like those shown in Fig. 2 were carried out for different concentrations of acetate at pH 7.4 (blue dots) and pH 6.4 (red dots). Each data point shows the mean growth rate from three or four independent experiments, as well as an error bar equal to twice the standard errors of the means. An exponential function with baseline of 0.3 h⁻¹ was fit to the data (blue and red curves). The baseline approaches the growth rate in minimal medium with 128 mM acetate as the sole carbon source (green line). For reference, the growth rate on 3 g liter⁻¹ of acetate, corresponding to 50 mM, is also shown (green dot). Notice that for some measurements the error bar is so small that it coincides with the measurement dot.