Bacteriophage Mu sites and functions involved in the inhibition of λ:: Mini-Mu growth

To better understand the nature of the mini-Mu-directed process which results in inhibition of λ:: mini-Mu growth we characterized spontaneous deletion mutants of the λ:: mini-Mu phage. On the basis of analysis of the deletion endpoints, mini-Mu replication functions, and integration and inhibition properties, the λ:: mini-Mu deletion mutants were divided into five classes which define the Mu sites and functions involved in λ::mini-Mu growth inhibition. Class 1 mutants, which still exhibit λ::mini-Mu growth inhibition, collectively delete all the Mu late functions encoded by the mini-Mu. Class 2 and 5 mutants, which show cis-dominant defects in inhibition and integration, delete the right and left mini-Mu attachment sites, respectively. Phages of Classes 3 and 4, which delete the Mu B or A and B genes, respectively, show recessive defects in growth inhibition. The properties of these mutants define the Mu replication functions, A and B, and the Mu attachment sites as essential for the inhibition of λ:: mini-Mu growth. The observation that the sites and functions essential for Mu replication also have requisite roles in the inhibition of λ:: mini-Mu growth suggests that inhibition results from mini-Mu-promoted replicative interference of λ::mini-Mu development.