[Mutants of ColE1 plasmid with altered expression of the colicin E1 immunity gene]

Mutagenesis with Tn1 transposon was used to isolate mutants of ColE1 plasmid with inactivated gene responsible for immunity to colicin E1. Cells containing such mutants synthesized active colicin E1 and were sensitive to its action. Spontaneous and UV-induced colicin synthesis was strongly changed in the mutants, as compared to the control. Mutations occurring outside the immunity gene, including those within the structural gene for colicin E1, could also affect the immunity gene expression.