Phage Multiplication on Two Hosts. Isolation and Activity of Variants of Staphylococcus Phage P1

Abstract

Analysis of phage activity by titration on 2 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 2 hosts, K1 and WF 145. Produced on K1 cells, the ratio of free phage assayed on 2 hosts is 1.3, whereas made on WF 145 cells, the free phage titrates in a ratio WF 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 WF 145 cells could not be explained on the basis of differences in adsorption onto or latent periods in the 2 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 WF 145 cells. Heat inactivation destroyed phage activity for K1 cells much more rapidly than for WF 145 cells. There was no interaction of heat killed and active phage on exposure to 59[degree]C. Evide..ce that the phage P14 is altered on passage through host WF 145 has been accumulated. The fact that phage particles surviving a heat treatment which destroyed all activity for K1 cells produce on strain WF 145 a mixture of 2 phages (one active on K1 and one[long dash]or both[long dash]active on strain WF 145) points to an unusual host effect on virus reproduction.