Characterization of a temperature-sensitive DNA replication mutant of Staphylococcus aureus

A temperature-sensitive DNA replication mutant of Staphylococcus aureus NCTC 8325 has been isolated and characterized. After transfer to the non-permissive-temperature (42 degrees C), DNA synthesis continued for 30 min and the mean DNA content increased by 56%. The amount of residual DNA synthesis was not reduced when the non-permissive temperature was raised, nor when chloramphenicol was added at the time of the temperature shift. During incubation at 42 degrees C, mutant bacteria accumulated the capacity to synthesize DNA after return to the permissive temperature (30 degrees C) in the presence of chloramphenicol. This capacity was lost when chloramphenicol was present at 42 degrees C. The properties of the mutant are consistent with a defect in the initiation of DNA replication at 42 degrees C.