Effects of solar ultraviolet radiations on Bacillus subtilis spores and T7 bacteriophage.

Spores of Bacillus subtilis HA 101 and the DNA polymerase I-defective mutant HA 101 (59) F were exposed to selected wavelengths of solar ultraviolet light and space vacuum during the return of Apollo 16. In addition, coliphage T7 suspensions were exposed to solar ultraviolet radiation as part of the Microbial Response to Space Environment Experiment. Optical filters were employed to provide different energy levels at wavelengths 254 nm and 280 nm. Dose-response curves for lethal and mutagenic effects were compared with ground-based data. A close parallel was observed between the results of solar radiation and ground tests with spores of the two strains. However, significantly greater inactivation of T7 bacteriophage was observed after exposure to solar ultraviolet radiation.