Transmission of Colicinogeny between Strains of Salmonella typhimurium Grown Together

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Abstract
Ability to produce colicines I, El, E2, K or B was transferred to Salmonella typhimurium strain LT2 by growth in broth with suitable colicinogenic strains of Escherichia colt or Shlgella sonnet When LT2 (coll), i.e. carrying the coliclne I factor, or LT2 (colB) were grown overnight in broth with LT2 col- (non-colicinogenic), c. 50% of the latter became coliclnogenlc; LT2 (colE2) and LT2 (colK) did not transmit; LT2 (colE1) transmitted to only c.0.1% of the acceptor population. But LT2 carrying either coll or colB in addition to colE2, colK or colE1, transmitted both factors. When overnight broth cultures of LT2 (coll) and LT2 col- were mixed and incubated c.40% of the latter acquired coll by 20 hr. (when the viable count had doubled); but only c.0.02% acquired coll in 3 hr. The low initial transfer results from the fact that in a stock culture of LT2 (coll) only c. 1/5000 bacteria are ''competent donors'', able to transmit coll. The later large increase in the proportion of colicinogenic bacteria probably results from ''epidemic spread'' of the coll 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 coll become competent donors. In a doubly coliclnogenlc strain most competent donors transmit both collcine factors. Aeration by shaking during incubation interfered with transmission of coliclnogeny, probably by abolishing the prolonged phase of slow growth of unaerated cultures. Growth in the presence of acriflavlne did not ''cure'' LT2 (coll) (colE2) of coliclnogeny, nor of ability to transmit LT2 (colEl) and LT2 (colE2) supported the epidemic spread of coll or colB about as well as did LT2 col-; but in LT2 (colK) the spread of coll was greatly reduced and that of colB somewhat reduced. The prior presence in an acceptor strain of one of the readily transmissible factors, coll or colB did not interfere with the epidemic spread of the other. But LT2 (coll) did not become a competent donor on accepting colE2 and, by inference, coll from LT2 (coll) (colE2).

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