Bacterial spores are remarkable in their resistance to chemical and physical stresses, including exposure to UV radiation. The unusual UV resistance of bacterial spores is a result of the unique photochemistry of spore DNA coupled with the efficient repair of accumulated damage. Exposure of bacterial spores to UV radiation results in the formation of a methylene-bridged thymine dimer, 5-thyminyl-5,6-dihydrothymine, a spore photoproduct, or SP, as the primary photoproduct. SP accumulates in UV-irradiated spores, however it is rapidly repaired upon germination, thus giving rise to the extraordinary UV resistance of bacterial spores. The repair of SP is catalyzed by the enzyme spore photoproduct lyase (SPL), and involves the direct reversal of SP to two thymines without base excision.

1: Structural insights into recognition and repair of UV-DNA damage by Spore Photoproduct Lyase, a radical SAM enzyme. Benjdia A, Heil K, Barends TR, Carell T, Schlichting I; Nucleic Acids Res. 2012;40:9308-9318. PMID:22761404

2: A radical transfer pathway in spore photoproduct lyase. Yang L, Nelson RS, Benjdia A, Lin G, Telser J, Stoll S, Schlichting I, Li L; Biochemistry. 2013;52:3041-3050. PMID:23607538

3: Rescuing DNA repair activity by rewiring the H-atom transfer pathway in the radical SAM enzyme, spore photoproduct lyase. Benjdia A, Heil K, Winkler A, Carell T, Schlichting I; Chem Commun (Camb). 2014;50:14201-14204. PMID:25285338