The Regulation of Colicin Synthesis and Colicin Factor Transfer in Escherichia coli K 12

Summary: Cells of Escherichia coli, newly infected with the colicin I factor (colI), showed an enhanced efficiency of transfer of this factor (HFC), and were also more likely to undergo lethal colicin synthesis, than were stably colicinogenic cells. Up to 20% of the cells of stably colI + strains were induced to produce colicin by ultraviolet irradiation, and from such irradiated cultures transfer of the colI factor occurred more efficiently. To account for these results, it is proposed that the colI factor exists as an autonomous non-chromosomal genetic element which sets up its own system of self-regulation within cells of stably colicinogenic strains.