[Expression of the resistance genes of plasmid RP4 in Escherichia coli cells grown by continuous cultivation].

The resistance to tetracycline decreased in Escherichia coli C600 cells containing plasmid RP4 and grown under the conditions of continuous cultivation. The population of cells containing plasmid RP4 is heterogeneous in the trait of tetracycline resistance, and most cells cannot grow in a selective medium with tetracycline at a concentration of 20 micrograms/ml. The decreased resistance to tetracycline was most pronounced for a glucose-limited chemostat culture and also in the presence of two plasmids, RP4 and pBS94 , in the cells. No decrease was found in the resistance to other drugs determined by plasmid genes.