Host range alteration of nocardiophage phiC following lysogenization of Nocardia erythropolis

Lysogens of the Mat Ce3 mating type strain of Nocardia erythropolis were isolated from infections by nocardiophage phiC. U.v. irradiation induced phage production in about 37% of the treated population. Phage produced from spontaneously induced populations appeared to undergo host controlled alteration(s) which allowed it to propagate in the normally resistant Mat cE2 mating type strains. A growth experiment performed with the infected Mat cE2 cells showed that the phage progeny failed to inherit the capacity to propagate in Mat cE2 strains. However, phage obtained from the Mat Ce3 lysogens could be propagated in Mat Ce3 hosts and still retain their ability to infect the Mat cE2 strains. The observations may represent a new type of host controlled phenotypic alteration of nocardiophage which acts on prophage.