Chloramphenicol releases a block in initiation of chromosome replication in a dnaA strain of Escherichia coli K12.

DNA-DNA hybridisation experiments show that chloramphenicol induces a burst of initiation from the oriC region of a dnaA46 mutant of Escherichia coli at 36.5 degrees C but not from the isogenic dnaA+ strain. Following this stimulation of initiation is in parallel with the induced stimulation of RNA synthesis caused by chloramphenicol in the same strain. This is consistent with the hypothesis that the stimulation of initiation in the dnaA mutant is the result of the stimulation of the synthesis of an RNA species.