Effect of Temperature on the Photobiology and Photochemistry of Bacterial Spores

Abstract

IN 1910, Becquerel¹ observed a fifteen-fold increase in the resistance of Bacillus anthracis spores to ultraviolet light when the irradiations were performed at liquid air temperature instead of at room temperature. More recently, Ashwood-Smith and others^2,3 found that Bacillus subtilis spores were 2.5 times more sensitive to ultraviolet light at −79° C than at 25° C. We show here that the very pronounced dependence of ultraviolet sensitivity on temperature of Bacillus megaterium spores is largely interpretable in terms of the temperature dependence of the production of the thymine-containing spore photoproducts called b and c^4–8. These products are not the cyclobutane pyrimidine dimers formed in vegetative cells. The experimental techniques have been described previously^6,8.