FIG. 4.

Na⁺ dependence of ATP synthesis coupled to hydrogen-dependent caffeate reduction. Cell suspensions of A. woodii (1.33 mg of protein/ml) were incubated in buffer in the absence of supplemental Na⁺ (•) or in the presence of 10 mM Na⁺ (○). Caffeate was added to a final concentration of 10 mM at the time indicated by the arrow. At time points indicated, samples were withdrawn and analyzed for cellular ATP content as described in Materials and Methods.