Photolyase repairs UV-induced lesions in DNA using light energy which is the principle for photoreactivation. Active photolyase contains the two-electron-reduced flavin cofactor. It was observed that photoreactivation of Escherichia coli was impaired at growth temperature ≥37℃, as were the decreased protein levels of photolyase in the cells. But levels of the phr transcripts (encoding photolyase) were almost unchanged at various growth temperatures.