Studies on calcium transport during growth and sporulation.

Experiments have been carried out to determine whether the active uptake of Ca2+ by sporulating Bacillus megaterium cells is driven by the pH gradient across the plasma membrane or by the membrane potential delta psi. Results from experiments using the ionophores nigericin and valinomycin which respectively dissipate the delta pH and the membrane potential, suggest that Ca2+ uptake during sporulation is driven by delta psi. It is further suggested that calcium is transported across the membrane via an antiport system in exchange for one or more protons. Arsenate and an inhibitor reported to be specific for membrane-bound ATPase, efrapeptin, have been used in other experiments to probe the role of ATP generation in calcium transport.