Effect of pH on acetate- and MCA- uptake. MBA4 was grown in minimal medium containing acetate or MCA, harvested and resuspended in potassium phosphate buffers of various pH values. Uptakes of 50 μM of [2-14C] labelled acetate or MCA were assayed for a period of 1 min. Squares represent acetate uptake of acetate-grown cells, circles represent acetate uptake of MCA-grown cells, and triangles represent MCA uptake of MCA-grown cells. Data shown are the means of three independent experiments, and the error bars represent the standard deviations.