Photochemical evidence for conformation changes in DNA during germination of bacterial spores.

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Abstract
Germinating spores exhibit brief periods of extreme resistance to UV radiation. In these experiments, a maximum of 55% of the population of Bacillus megaterium spores survived a dose which permitted the survival of only 0.25% of the dormant spores. These experiments correlated this resistance with a decrease in production of thymine-containing photo-products. At 3 min., the time of peak resistance and thymine photo-product production was nearly an order of magnitude less than that found in cells or dormant spores. These experiments suggest that the DNA in spores, germinating spores and vegetative cells exist in different environments which would lead to different types and amounts of photoproducts produced and thus to differences in survival after UV.