Direct selection of tetracycline-sensitive Escherichia coli cells using nickel salts.

In this report, a new method for the selection of tetracycline-sensitive Escherichia coli cells from a mixed population is described. This method is simpler and more effective than previous methods, does not utilize toxic reagents, and allows selection in liquid as well as solid media. This method should be of considerable aid in molecular cloning procedures involving inactivation of the tetracycline-resistance genes encoding the energy-dependent efflux of the antibiotic, as well as in the study of the function of tetracycline-resistance elements such as transposons and integrons.