A Study of the Mechanism of Inhibition of Bacteriophage Multiplication by Chymotrypsin

SUMMARY: When 0·01% chymotrypsin is added to mixtures of rhizobium bacteriophage and bacteria in liquid cultures, the multiplication of phage is prevented and the phage gradually becomes inactive. The rate and extent to which phage and bacteria combine are unaffected by the chymotrypsin whose effect seems directed against an early stage in the interaction between the two. This stage persists, on average, for less than 1 min. from the moment of combination. A phage particle combined with a bacterium becomes inactive and the bacterium is thus protected against lysis and remains able to multiply. Chymotrypsin does not interfere with combination between phage and bacteria killed by ultraviolet radiation: the combination leads to loss of phage activity irrespective of the presence of chymotrypsin. The multiplication of the phage is unaffected by previous incubation of either the phage or of the host bacteria separately with 0·01% chymotrypsin.

Chymotrypsin has no effect on phage-host interaction in an agar medium.