STUDIES ON THE COBALT-RESISTANCE IN ESCHERICHIA COLI

I. STUDIES ON THE PERMEABILITY OF CELL WALL OF COBALT RESISTANT AND SENSITIVE ESCHERICHIA COLI TO COBALT ION

Abstract

The studies on the cobalt-ion-permeability in the cobalt-resistant mutantof Escherichia coli K-12 isolated in our laboratory confirmed that:
(1) the cobalt penetrates cobalt-resistant cells much more readily than it does sensitive cells;
(2) the cobalt-resistant cells grown in synthetic culture media can fix about twice as much cobalt ion as the sensitive parent cells;
(3) when grown in a synthetic medium containing radioactive cobalt ions, the resistant cell can proliferate as well as in a non-radioactive cobalt-containing medium and fix cobalt ion about 1.5 to 2 times higher than the extracellular concentration of radioactive cobalt;
(4) when grown in nutrient broth, the amount of cobalt which permeates into bacterial cells is higher than in the case of synthetic medium cultivated cells, and no marked difference was found between the cobalt-resistant and-sensitive cells.
This study further suggests that the mechanism of cobalt-resistance in this mutant cell was not due to the cobalt-permeability barrier, and that the resistant cell has more affinity for cobalt ion than the sensitive cell, particularly those cells which were grown in a synthetic medium.