Correlation between survival, ability to rejoin DNA and stability of DNA after preirradiation inhibition of protein synthesis in a rec mutant of Escherichia coli K12.

A 90 min inhibition of protein synthesis induced by starvation for amino acids (AA-) or by treatment with chloramphenicol (CAP) prior to UV irradiation (2.5 Jm-2) increased the resistance of the strain Escherichia coli K12 SR19 to UV radiation more than ten-fold. Under these conditions, cultures in which protein synthesis was inhibited before the UV irradiation rejoin short regions of DNA synthesized after the irradiation to a normal-size molecule, whereas an exponentially growing culture does not rejoin DNA synthesized after UV irradiation to a molecule of a normal size. In the exponentially growing culture both the parental and the newly synthesized DNA are unstable after the irradiation. In cultures with inhibited protein synthesis only the parental DNA is somewhat unstable. In Escherichia coli K12 SR19 where protein synthesis was inhibited before the irradiation, a correlation between the survival of cells, the ability to rejoin short regions of DNA synthesized after UV irradiation and a higher stability of both parental and newly synthesized DNAs could be demonstrated.