Positive selection for loss of tetracycline resistance

Abstract

A simple technique was devised that allows direct plate selection of tetracycline-sensitive clones from a predominantly tetracycline-resistant [Escherichia coli and Salmonella typhimurium] population. The technique is especially useful in genetic methodologies based on the use of tetracycline resistance transposons, such as Tn10. Potential uses of the method include selection of deletion mutants, fine-structure mapping, generalized mapping, construction of multiply marked strains, elimination of tetracycline resistance transposons and plasmids, and cloning. The technique is based on the finding that tetracycline-resistant cells are hypersensitive to lipophilic chelating agents, such as fusaric acid. Apparently certain metal ions critically facilitate tetracycline uptake. Possible molecular mechanisms for tetracycline resistance are suggested.