Resistance of Bacillus Subtilis Spores Lacking Either Nucleotide Excision Repair or Spore Photoproduct Lyase to Ultraviolet (UV) Radiation from Artificial or Natural Sources

Xue, Yaming, Resistance of Bacillus subtilis spores lacking either nucleotide excision repair or spore photoproduct lyase to ultraviolet (UV) radiation from artificial or natural sources. Master of Science (Biomedical Sciences), June 1996, pp., 4 tables, 12 illustrations, references, 38 titles. Exposure of bacterial spores to UV radiation causes the accumulation of a unique pyrimidine dimer in the DNA, “spore photoproduct” (SP). In Bacillus subtilis, two distinct DNA repair pathways are used for removal of SP: general nucleotide excision repair (the uvr parthway), or the SP-specific enzyme SP lyase (the spl pathway). Spores of four strains of Bacillus subtilis differing in their repair capabilities were irradiated under either artificial or solar UV. To determine the biologically-relevant cumulative UV dose under each irradiation condition, a sporocidal dosimeter was constructed. The results showed: (i) Both uvr and spl pathways contributed to the survival of spores under all tested conditions. The spl pathway was more efficient than uvr pathway in repairing the DNA damage caused by UV-C and solar UV-A, but no significant difference was noted in repairing DNA damage caused by UV-B or full-spectrum solar UV. (ii) Exposure of spores to solar UV can cause cellular lethal damage which is reparable by neither repair pathway.