The DNA synthesis of bacteriophage phiX174 in Escherichia coli HF470S, a mutant temperature sensitive in the initiation of DNA replication (dnaHts), has been examined. In HF4704S cells, phiX174 can grow normally at 27 degree C whereas the phage cannot grow after the cessation of DNA synthesis of the host cells at 42 degrees C. Upon infection, phiX174 DNA can be injected into the host cell and the parental replicative form can be formed, but the progency replicative form cannot be synthesized at 43 degrees C in the absence of host DNA synthesis. The progency replicative form cannot be synthesized at 27 degrees C in the presence of 30 mug chloramphenicol/ml in the host cell which has been incubated for 74 min at 43 degrees C followed by transfer to 27 degrees C in the presence of 30 mug chloramphenicol/ml. When 30 mug chloramphenicol/ml is added later than 5 min after the temperature shift-down to 27 degrees C, the progency replicative form synthesis is not inhibited. Thus, the host cell function, for which the gene dnaH is responsible, has been shown to be essential to the progency replicative form production.
Chloramphenicol Coliphages