Cationic uptake and exchange in Salmonella enteritidis

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Abstract
The use of inorganic cations in cells and purified cell walls of Salmonella enteritidis was investigated. Both the uptake and exchange of radioactive cations were energy-dependent and influenced by pH, by dialysis time and temperature, and by the ionic content of the surrounding medium. Cell walls bound 47Ca2+ to the greatest extent, followed in order by 65Zn2+, 54Mn2+, and 59Fe3+. Another determining factor for cationic exchange was valency, with divalent cations exchanging to the greatest extent, followed by trivalent and monovalent cations, respectively. The greatest amount of exchange occurred between a radioisotope and a stable isotope of the same species. All losses of radioactivity were dialyzable indicating that this exchange involves very small moieties, perhaps the cation alone. Both 2,4-dinitrophenol (DNP) and N,N′-dicyclohexylcarbodiimide (DCCD) significantly decreased autologous exchange, cationic exchange, and cationic uptake in either cells or cell walls. It was postulated that these two compounds either inhibited ATP hydrolysis or reacted with membrane sites such that the membrane could no longer undergo configurational changes associated with cationic transport or exchange.

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