Diphtheria-phage inhibitor produced by treating the host bacterium with oleic acid.

In work previously carried out in this laboratory it was shown that the nonionic surface active agent polyoxyethylene sorbitan monooleate (Tween 80) inhibited the adsorption of a Corynebacterium diphtheriae phage to its host cell (Groman and Bobb, 1955). During this investigation oleic acid, a known contaminant of Tween 80, was also tested for its ability to inhibit phage adsorption. In contrast to Tween 80, oleic acid appeared to enhance adsorption at a concentration of 20 ,g/ml while causing no direct inactivation of phage in the control. In subsequent studies with the same phage-host system, oleic acid was tested for its effect on lysis in broth, and at 15 to 20 ,ag/ml prevented lysis while causing no apparent inhibition of bacterial growth. The conclusion suggested by these findings, namely that oleic acid inhibited phage reproduction subsequent to adsorption, prompted further investigation of the phenomenon. As a result of the experiments to be reported in this paper it is now clear that oleic acid plays a role in the release and activation of a phage inhibitor from the bacterial host. Thus the apparent effects of oleic acid on phage adsorption and reproduction can be explained by rapid extracellular inactivation of phage by the inhibitor.