Evidence for the active role of bacteriophage in the conversion of nontoxigenic Corynebacterium diphtheriae to toxin production.

In a previous report (Groman, 1953a) it was concluded that toxigenic Corynebacterium diphtheriae which are recovered following exposure of a nontoxigenic strain to specific bacteriophage result from a direct conversion to toxigenicity' rather than from selection of toxigenic mutants. This conclusion was supported and strengthened by the work of Barksdale and Pappenheimer (1954) in their study of the same phage-host system. It has been proposed as a working hypothesis (Groman, 1953a) that conversion to toxigenicity is a direct consequence of the establishment of the lysogenic state. This proposal was based primarily on the one-to-one relationship existing between toxigenicity and lysogenicity under all conditions including those in which selection by phage was inoperative. This fact, together with the stability of the converting principle in the presence of desoxyribonuclease (Groman, 1953b), made it appear unlikely that a single principle acting independently of phage was involved in the conversion process. In the present work additional observations bearing on the conversion process are presented, and possible mechanisms for the phenomenon are examined in the light of these data.