INVOLVEMENT OF 2 GENES OF SUPERINFECTING PHAGE KAPPA IN CURING AND INDUCTION OF PROPHAGE PSI IN SERRATIA-MARCESCENS HY

Prophage psi carried along with prophage y by Serratia marcescens HY i s subject of moderate curing at heteroimmune superinfection of cells f rom stationary phase with phage kappa. Curing becomes considerably mor e frequent when the bacteria are non-lysogenic for y. Both psi,y-doubl e-lysogenic and psi-single-lysogenic cells with a mutation in the ink gene are very efficiently cured of psi if infected by kappatay, althou gh this mutant was characterized as being deficient in transactivation of certain genes in prophage y. On the other hand to get efficiently cured after kappa wild-type infection these cells too must be devoid o f a y prophage. Thus a y function turned on by tay+ seems to counterac t the elimination of psi. However, interestingly enough psi curing is boosted by a further y function under special circumstances. Efficient curing depends on an intact kappatap gene, a gene reported to cause t ransactivation of certain psi genes. Curing at kappatay infection is s pecifically accompanied by induction of the psi prophage in a part of the infected cells. However, there is no such induction at kappa wild- type infection, either in the absence or presence of a y prophage. An explanation of these findings is suggested which includes an antirepre ssive effect exerted on psi and a hypothetical interaction between the products of genes tap and tay.