Verification of the SWITCH Test for Determination of Cyto- and Genotoxicity by Simulated Space Radiation Qualities.

Before humans embark on long term space missions, it is very important to understand hazards posed by space radiations. Radiations above a certain level can lead to death or have long term effects including cancer. This study is based on the bacterial SWITCH test which has the capability to report on genotoxicity as well as cytotoxicity of space quality radiations (as well as on toxicity of chemicals and other agents) and has been developed by the Radiation Biology group at German Aerospace Center (DLR). The test was used in this study to obtain data on genotoxicity and cytotoxicity of different qualities of X-rays as well as of accelerated heavy ions, the latter representing a very important component of space radiation. It was shown that toxicity of radiations varies with its quality. Radiation energy (dose) is only one factor contributing to the genotoxicity and cytotoxicity of radiations, another important factor is the linear energy transfer (LET). Another important outcome was that cytotoxicity and genotoxicity are independent factors and are not correlated. An effort was also done to understand the structure of SWITCH plasmid present in these bacteria by using restriction analysis to analyze SWITCH and its precursor plasmids