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 ⁵⁴ Mn²⁺ to measure Mn²⁺ influx, and the use of surrogate radioisotopes when the primary radioisotope is not available, e.g., use of ⁶³ Ni²⁺ or ⁵⁷ Co²⁺ in place of ²⁸ Mg²⁺ to measure Mg²⁺ influx. Both vacuum filtration and centrifugation assays are described. In addition, the use and misuse of chelating agents is discussed.