Genetic studies with two prophages naturally resident in Serratia marcescens HY

Summary Serratia marcescens HY was cured of two native prophages, and y. Curing occurred after infection with temperate phage , but the cured strains did not become -lysogenic. One of them has been simultaneously cured of both and y. Recognition of cured colonies was based on their loss of immunity towards the respective phage. Whereas plates on the singly cured strains, it does not plate on the doubly cured strain. However, infection of it with leads to a limited phage multiplication, the average burst size being low and only part of the infected cells producing phage at all. The ability of the strain to serve as indicator for can be restored by relysogenization with either or y. In addition, some further relations between , , and y are reported in this paper.Abbreviations moi multiplicity of infection - A absorbance (optical density) - NB nutrient broth - BS buffered saline - EMB eosine methylene blue - thy thymine - leu leucine This work was supported by the Deutsche Forschungsgemeinschaft. The technical help of Miss A. Varela and Mrs. I. Steiger in some experiments is appreciated.