Role of post-replication and excision repair mechanism in the induction of Trp+ revertants of UV-irradiated Escherichia coli.

Both the post-replication and the excision repair mechanism participate in the induction of Trp+ revertants in Escherichia coli B/r Hcr+ thy trp after a UV-irradiation. At low radiation doses (surviving cell fraction greater than 10(-1) most Trp+ reversions are due to post-replication repair mechanism while at high doses (surviving cell fraction less than 10(-1)) the Trp+ reversions arise probably as the result of an inaccurate excision repair. The absolute accuracy of repair processes decreases with increasing radiation dose.