DNA bipyrimidine photoproduct repair and transcriptional response of UV-C irradiated Bacillus subtilis.

Vegetative wild-type and DNA repair-deficient (homologous recombination, recA and nucleotide excision repair, uvrB) Bacillus subtilis cells were exposed to UV-C radiation. Colony formation, DNA bipyrimidine photoproducts and gene expression were measured during cell recovery. Gene expression was measured after 60 min cell recovery where 50% (wild-type), 30% (recA) and 8% (uvrB), respectively, of the UV-C induced DNA photoproducts were repaired. We examined changes in the gene expression following UV exposure in wild-type and both repair-deficient strains. A set of known and unknown genes were found to be significantly up-regulated in wild-type B. subtilis cells, whereas no or lower gene induction was determined for both mutant strains. In addition, the possible roles of newly identified UV-responsive genes are discussed with respect to cellular recovery following exposure to UV irradiation.