Genetic and functional basis of the reduction effect in bacteriophage (10X174

The (10X174 reduction effect describes a plasmid-based inhibitory phenomenon that mimics the superinfection inhibition found in wild phage populations. In this effect, when a portion of the (10X174 genome - the 3 ' end of the pilot protein gene (H), the 5' end of the replication gene (A), and the H-A intergenic region - is present on a plasmid in the host cell, almost complete protection from phage infection occurs. Here we demonstrate that only the phage pilot protein H portion of the plasmid is sufficient for the observed inhibition, that protein synthesis is necessary for inhibition to occur, that inserting the entire H gene in the plasmid may also impart a blocking effect, and that partial to complete recovery from this inhibition is possible with minimal viral evolution.