The Relationship between Filaments, Killing and Restoration in Irradiated Escherichia coli Strain B

SUMMARY: The morphology of normal and 5-bromouracil (5-BU) containing Escherichia coli strain b was examined after exposure of the bacteria to X-rays (under aerobic and anoxic conditions) and to ultraviolet light (u.v.). The majority of filaments which developed after irradiation either originated a microcolony or disintegrated. Post-irradiation incubation with chloramphenicol (CMP) restored the ability of some of the bacteria to originate viable colonies by suppressing filament formation, particularly in the case of normal thymine-containing bacteria. CMP also prevented the disintegration of filaments, provided it was applied before they reached a critical length. This was particularly evident in 5-BU-containing bacteria. It is suggested that incubation with CMP may allow wall synthesis to proceed in the absence of protein synthesis, thereby enabling thickening of the wall to take place, so that normal division can resume on removal of the CMP.