Phage Multiplication on Two Hosts. Isolation and Activity of Variants of Staphylococcus Phage P 1 ∗

Abstract

Summary

Analysis of phage activity by titration on two hosts has revealed the presence of variants hitherto undetected in stock phage P₁. One isolate, Phage 14, exhibits great changes in titration ratio on passage through the two hosts K₁ and WF 145. Produced on K₁ cells, the ratio of free phage assayed on two hosts is 1.3, whereas made on 145 cells, the free phage titrates in a ratio 145/K₁ of ca 40. This occurs regardless of the host employed in previous passage and is reproduced in the very first burst from infected cells. Attempts to isolate different strains from this phage by usual plaque isolation technics were not successful. The high ratio obtained with free phage made on 145 cells could not be explained on the basis of differences in adsorption onto or latent periods in the two hosts. The difference was traced to the production of a large number of particles from host 145 which adsorbed on K₁ but formed no plaques. No evidence was found for an inhibitor of K₁ activity associated with phage 14 production on 145 cells. Heat inactivation destroyed phage activity for K₁ cells much more rapidly than for 145 cells. There was no interaction of heat killed and active phage on exposure to 59°C.

Evidence has been accumulated which indicates that the phage P₁₄ is altered on passage through host 145. The fact that phage particles surviving a heat treatment which destroyed all activity for K₁ cells produce on strain 145 a mixture of two phages (one active on K₁ and one—or both—active on strain 145) points to an unusual host effect on virus reproduction.