FIG. 1.

(A) Effect of external pH on specific growth rate of Bacillus sp. strain TA2.A1 grown in pH-controlled batch culture at the pH indicated. The growth rate (h⁻¹) was determined in the exponential phase of growth. The effect of external pH on (B) internal pH, (C) Δψ (▪) and ZΔpH (○), and (D) proton motive force (▴) was determined. Exponentially growing cells were taken from pH-controlled batch culture at the pH indicated, and measurements were made as described in Materials and Methods. The values reported are the means of three independent experiments, and the standard error associated with these determinations is shown.