Abstract
Recent studies have shown that a range of spore and non-spore forming bacteria can be isolated from the stratosphere. The aim of the work reported here was to determine some of the factors which may increase the rate of survival of Bacillus simplex and Staphyloccus pasteuri in this UV-rich environment. The results show that, while both UV-B and UV-C are lethal to both B.simplex and S.pasteuri, "shading" by particulates, similar to those likely to present in the stratosphere, as well as the presence of low temperature and nutrient limitation are likely to increase the ability of bacteria to survive in the UV-rich stratosphere. Although the degree of protection to UV by the factors tested here afforded is relatively small, any degree of increased survival is likely to provide a selective advantage, allowing bacteria to survive in the stratosphere or perhaps deeper in space.