CA2+ uptake in an asporogenous mutant strain of Bacillus megaterium.

Some properties of Ca2+ accumulation were examined in Bacillus megaterium mutant 3-12 which cannot sporulate owing to a lack of dipicolinic acid. The steady-state intracellular content of Ca2+ was half-saturated at 0.06 mM. Ca2+ was accumulated up to its plateau in 30 min. There were two classes of Ca2+ accumulation, high-affinity and low-affinity, both of which were mostly energy-dependent, and there was a small amount of energy independent Ca2+ binding. Exchange of Ca2+ accumulated in the cells for the external Ca2+ in the medium was observed. The highest rates of exchange were evident in the cells harvested when Ca2+ accumulation reached its peak.