Magnesium, manganese, and divalent cation transport assays in intact cells

Protocols are described for the measurement of radioisotopic cation influx and efflux in bacteria using Salmonella as a model system. Methods are discussed for both the use of primary radioisotopes for measurement, e.g., using 54Mn2+ to measure Mn2+ influx, and the use of surrogate radioisotopes when the primary radioisotope is not available, e.g., use of 63Ni2+ or 57Co2+ in place of 28Mg2+ to measure Mg2+ influx. Both vacuum filtration and centrifugation assays are described. In addition, the use and misuse of chelating agents is discussed.