Transfer of colE1 and colE2 During High-Frequency Transmission of colI in Salmonella typhimurium

SUMMARY: In stock cultures of Salmonella typhimurium strain lt2 carrying the factor determining the production of colicine I, colI, together with other colicine factors, colE1 or colE2, most of the small minority of bacteria competent to act as donors of colI also transmit their E factor. Most noncolicinogenic bacteria which acquire an E factor at the same time as colI become competent to transmit both factors. Similarly, bacteria carrying factors colE1 and/or colE2 accept colI normally and then usually become competent to transmit both colI and the E factor(s) they already carry. In experiments on the kinetics of colicine factor transmission by lt2 (colE1) (colE2) newly infected with colI, most acceptor bacteria that acquire any colicine factor acquire all three factors, within 5–20 min. for most pairs, but within 1 min. for a very few. When conjugation is interrupted within 5 min. of mixing, fewer acceptor bacteria acquire all three factors; all single-factor and two-factor classes are then represented, so the order of transfer of the three factors must differ in different pairs. Bacteria carrying colE2 do not transfer this factor to donor bacteria from whom they acquire colI; but they become able to transmit colE2 (and presumably colI also) within 15–20 min. of acquiring colI. Other observations support the hypothesis that in most competent donors carrying colE1 and/or colE2, these factors multiply autonomously, as does colI.