Regulation of λ rex Expression After Infection of Escherichia coli K by Lambda Bacteriophage

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Abstract
The ability of Escherichia coli K to support bacteriophage T4rII replication starts to decline at 3 to 6 min after infection by λ. This inhibition appears to depend on expression of the λ rex + gene, since little inhibition was observed following infection by a λ rex mutant or by a hybrid bacteriophage λi 434 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 cI- rex operon because they are also known to be required for repressor (cI product) synthesis. Functional cIII, O, P genes are not necessary for ample rex product synthesis. We also observed full rex expression after infection by λ sus cI mutants, suggesting that rex and repressor are separate gene products and that repressor is not required for inhibition of T4rII replication. We also report experiments with a rex mutant that is not leaky when in a lysogen but is sufficiently leaky shortly after infection to cause inhibition of T4rII replication.