Regulation of xrex Expression After Infection of Escherichia coli K by Lambda Bacteriophage LAZARUS

on expression of the Xrex+ gene, since little inhibition was observed following infection by a Xrex mutant or by a hybrid bacteriophage Xii44 which lacks a functional rex gene. For promotion of the synthesis of rex product, cII+ and N+ genes are required and can act trans, whereas cY+, also required, must be cis to a rex+ gene. These genes presumably play a role in the transcription of the cd-rex operon because they are also known to be required for repressor (cI product) synthesis. Functional ciiI, 0, P genes are not necessary for ample rex product synthesis. We also observed full rex expression after infection by XsuscI mutants, suggesting that rex and