The ability of Escherichia coli K to support bacteriophage T4rIL replication starts to decline at 3 to 6 min after infection by X. This inhibition appears to depend 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 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.

Cadaverine was found in bacteriophage T4 when the host cells of Escherichia coli K-12 were grown in complex media and aerated by agitation. Only traces of cadaverine were found if the host was grown and agitated in synthetic medium or was aerated by vigorous bubbling in a complex medium. When the host cells were grown anaerobically in a complex medium, cadaverine became the major polyamine in the progeny phage. The polyamine content comprised 80% cadaverine, 14% spermidine (or its recently discovered homologue, N-3-aminopropyl-1, 5-diaminopentane), and the remainder putrescine. The conditions that favored appearance of cadaverine are known to be required for induction of lysine decarboxylase. It was shown that lysine was the sole source of bacterial cadaverine.