Manganese Active Transport in Escherichia coli

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 54 Mn was used, manganese transport showed saturation kinetics with a K m of 2 × 10 −7 m and a V max of 1 to 4 nmoles/min per 10 12 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 54 Mn uptake, but only when added at concentrations 100 times higher than the K m for manganese. Active transport of manganese is temperature- and energy-dependent: uptake of 54 Mn 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.