Cell division in Escherichia coli: evidence for regulation of septation by effector molecules

Evidence regarding the regulation of cell division has been obtained from the study of septation in a mutant of Escherichia coli. The mutant, MX74T2 ts52, gradually stops dividing when transferred from 30 to 41°C in rich medium, but forms long filaments and continues to synthesize DNA and protein. These filaments serve as test objects for the investigation of the regulation of septation. A synchronous cell division of the filaments is induced after 15 minutes, even at 41°C, by the addition of chloramphenicol (100 μg/ml.), rifampicin (200 μg/ml.), or by transfer to minimal medium. Blocking of protein formation with puromycin (500 μg/ml.) or amino-acid analogues does not permit septation. Thus, septation appears to be coupled to inhibition of peptide bond formation rather than protein synthesis. A model for the control of cell division is proposed in which a small effector molecule that is related to peptide bond formation is needed for septation.