Inheritance of nocardiophage phi EC in matings of nocardial lysogens

Lysogens of Nocardia erythropolis were mated with nonlysogenic strains to study the inheritance of the phi EC prophage. Crosses between lysogenic strains of the Mat-Ce mating type and nonlysogenic Mat-cE strains produced Mat-cE lysogens at a recovery rate of 17%, whereas recombination frequencies between chromosomal traits were about 2.3 x 10(-5). Crosses of lysogenic Mat-cE mating types with nonlysogenic Mat-Ce produced Mat-Ce lysogens at a recovery rate of 19%, whereas recombinants for chromosomal traits were recovered at only 1.8 x 10(-5). Crosses of homologous mating types, lysogenic Mat-Ce with nonlysogenic Mat-Ce or lysogenic Mat-cE with nonlysogenic Mat-cE, failed to transfer the prophage. It was concluded that the phi EC prophage exists as a plasmid and can be transferred at high frequencies with patterns of transfer controlled like typical nocardial fertility. Evidence that the prophage may also exist as an integrated element was observed from recombination analyses.