title: Facilitated transport of calcium by cells and subcellular membranes of Bacillus subtilis and Escherichia coli.
abstract: The level of calcium in growing cells is lower than that in the growth medium. Non-energy-dependent uptake of 45-Ca by log-phase cells of Bacillus subtilis occurs under two conditions: at 0 C or in the presence of m-chlorophenyl carbonylcyanide hydrazone. Similar uptake, but quantitatively less, occurs with Escherichia coli cells under the same conditions. Membrane vesicles prepared from B. subtilis or E. coli accumulate 45-Ca by a process that does not depend on added energy sources and is not inhibited by the respiratory poison cyanide. The properties of calcium transport in all cases is consistent with carrier-mediated, facilitated transport with specificity Ca-2+ greater than Sr-2+ greater than Mn-2+ greater than Mg-2+. Upon transfer of cells from 0 C to 20 C, pre-accumulated 45-Ca is released. Heat-killed cells do not accumulate 45-Ca and calcium is released by cells upon addition of toluene (under conditions that do not cause visible lysis). These results suggest that the facilitated uptake of calcium may be utilizing a transport system that normally is responsible for the energy-dependent excretion of calcium from the cells.
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism; D001412:Bacillus subtilis / Q000378:metabolism*; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002250:Carbon Radioisotopes; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008773:Methylphenazonium Methosulfate / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology*; D011392:Proline / Q000378:metabolism; D013324:Strontium / Q000494:pharmacology; D013347:Subcellular Fractions / Q000378:metabolism; D013696:Temperature
chemical_list: D002250:Carbon Radioisotopes; D009570:Nitriles; D008773:Methylphenazonium Methosulfate; D008345:Manganese; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D011392:Proline; D008274:Magnesium; D001205:Ascorbic Acid; D002118:Calcium; D013324:Strontium