KCS

Ultraviolet (UV) radiation is well known to cause DNA damages such as single strand breaks, and double strand breaks due to pyrimidine dimer. Interestingly, some species of bacteria have radiation resistance such as deinococcus radioduran. Recently, Harris et al developed four kinds of UV-resistant E. coli strains mutated from K-12 MG1655 strain. To characterize what makes these strain UV endurable, they used Pulse Field Gel Electrophoresis (PFGE) and sequencing. They reported recovery of UV-induced damage and they interpreted their result that UV-resistance is due to enhanced DNA repair mechanism. However, we suspect that DNA itself may have the characteristic of UV-resistance. Thus, here we performed single DNA molecule experiment to identify the resistance mechanism whether DNA itself is resistant or not by observing single-stranded breaks on the genomic DNA.