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Abstract
Dps is a DNA-binding protein that plays a critical role in protecting Escherichia coli cells from many types of environmental stresses, such as UV radiation, gamma radiation, oxidative stress, thermal stress, and acid/base shock. It is the most abundant protein during stationary phase, during which it binds to bacterial DNA in a non-specific manner, forming a biocrystal. It has also been implicated in other important protective processes, such as the genetic regulation of key enzymes involved in DNA repair. In this study, we examined the ability of Dps to protect the sequence integrity of DNA against UV-induced mutations + during stationary phase by using E.coli K-12 strains ZK126, a wild-type Dps control, and ZK1146, an isogenic dps mutant. Specific mutations in the quinolone resistancedetermining regions (QRDR) of gyrA and gyrB are known to confer resistance to nalidixic acid. After UV irradiation, a significantly higher level of survival of the ZK1146 strain was observed in the presence of nalidixic acid, compared to the ZK126 strain. This confirms that Dps confers protection against UV-induced mutations. Furthermore, our results suggest that Dps acts to regulate the frequency of mutation in E. coli during stationary phase.