Evelyn Witkin of Rutgers University on Discovering the SOS Response in Bacteria

Evelyn Witkin, working at Cold Spring Harbor, found that after UV irradiation of E. coli only 4 colonies survived per million bacteria, with resistance to UV and X-ray radiation raised roughly 100-fold. She proposed that UV activates at least 43 genes that stay silent in healthy cells and turn on when DNA is damaged, forming the SOS response, a DNA damage repair mechanism. The concept, named by Miroslav Radman, was built on repair pathways such as photoreactivation and excision repair, with RecA triggering repair genes when stalled replication forks expose single-strand DNA.