Manganese Active Transport in Escherichia coli

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Abstract
Manganese was accumulated by cells of Escherichia coli by means of an active transport system quite independent of the magnesium transport system. When the radioisotope 54Mn was used, manganese transport showed saturation kinetics with a Km of 2 × 10−7m and a Vmax of 1 to 4 nmoles/min per 1012 cells at 25 C. The manganese transport system is highly specific; magnesium and calcium did not stimulate, inhibit, or compete with manganese for cellular uptake. Cobalt and iron specifically interfered with 54Mn uptake, but only when added at concentrations 100 times higher than the Km for manganese. Active transport of manganese is temperature- and energy-dependent: uptake of 54Mn was inhibited by cyanide, dinitrophenol, and m-chlorophenyl carbonylcyanide hydrazone (CCCP). Furthermore, the turnover or exit of manganese from intact cells was inhibited by energy poisons such as dinitrophenol and CCCP.