On the process of cellular division in Escherichia coli: replication of the bacterial chromosome under control of prophage P2.

The temperature-sensitive mutant CRT46 of Escherichia coli K12 is unable to initiate new rounds of DNA replication at 42 degrees C. Mutants of bacteriophage P2 have been isolated, which, in the prophage state, allow mutant CRT46 to grow at 42 degrees C. The lysogenic bacteria that grow at 42 degrees C are apparently replicating under the control of prophage P2, which substitutes for the bacterial initiation system. The ability of prophage P2 cause this suppression phenomenon depends on the position of the prophage on the bacterial chromosome. Those lysogenic strains that are able to grow at 42 degrees C all carry the prophage close to metE. The P2 mutants that allow CRT46 to grow at 42 degrees C have insertions in the early region of the P2 genome. The suppression requires the cis-acting protein formed by gene A of P2.