Transfer of the Colicin I Factor in Escherichia coli k12 and its Interaction with the F Fertility Factor

Abstract

A series of Escherichia coli K12 strains of various mating types was made resistant to colicin I (coll-r) and colicinogenic for this character (colr+). In the absence of the F sex factor, the number of "competent donors" of colI in broth cultures of colicinogenic strains was about 1%. Transfer of colI to non-coli-cinogenic strains reached about 7-10% within 2 hr of mixing, and between 50 and 100% after incubation overnight. Cells newly infected with colI transfer more efficiently, and can infect over 90% of a recipient strain with colI within 1 hr of mixing (high-frequency colicino-geny transfer, HFC). When the F factor was present in the colicinogenic donor strain of a mixture, colI transfer was reduced; when F was present the non-colicinogenic recipient, colI transfer was increased. The colicin I factor appeared to be transferred by a series of Hfr strains as an extrachromosomal element.