SUMMARY: Ability to produce colicines I, E1, E2, K or B was transferred to strain LT2 by growth in broth with suitable colicinogenic strains of or When LT2 (), i.e. carrying the colicine I factor, or LT2 () were grown overnight in broth with LT2 (non-colicinogenic), 50 % of the latter became colicinogenic; LT2 () and LT2 () did not transmit; LT2 () transmitted to only 0.1 % of the acceptor population. But LT2 carrying either or in addition to or transmitted both factors.

When overnight broth cultures of LT2 () and LT2 were mixed and incubated 40 % of the latter acquired by 20 hr. (when the viable count had doubled); but only 0.02 % acquired in 3 hr. The low initial transfer results from the fact that in a stock culture of LT2 () only 1/5000 bacteria are ‘competent donors’, able to transmit The later large increase in the proportion of colicinogenic bacteria probably results from ‘epidemic spread’ of the factor amongst the acceptor population, initiated by the few acceptor bacteria which originally receive it. It is supposed that most bacteria which have just acquired become competent donors. In a doubly colicinogenic strain most competent donors transmit both colicine factors.

Aeration by shaking during incubation interfered with transmission of colicinogeny, probably by abolishing the prolonged phase of slow growth of unaerated cultures. Growth in the presence of acriflavine did not ‘cure’ LT2 () or LT2 () () of colicinogeny, nor of ability to transmit.

LT2 () and LT2 () supported the epidemic spread of or about as well as did LT2 ; but in LT2 () the spread of was greatly reduced and that of somewhat reduced. The prior presence in an acceptor strain of one of the readily transmissible factors, or did not interfere with the epidemic spread of the other. But LT2 () did not become a competent donor on accepting and, by inference, from LT2 () ().


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