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.

Manganese is growth inhibitory for Escherichia coli. The manganese concentration required for inhibition is dependent upon the magnesium concentration of the medium. Mutants have been isolated which are partially resistant to manganese inhibition in both liquid and solid media. From conjugation experiments, the genetic locus for manganese-resistance, mng, appears to be between 34 and 37 min on the E. coli genetic map. Experiments with radioactive 28Mg on August 1, 2020 by guest