Mutagenesis of Bacillus subtilis spores under simulated space environment

Abstract

Bacterial spores can survive in extreme environments and potential agents of interplanetary dispersal. In the preflight project of EXPOSE, various microorganisms are exposed to stresses to be encountered during the flight, and we are studying the survival and mutagenesis of Bacillus subtilis spores. In the first simulation experiment, dry spores are exposed to high vacuum (about 10⁻⁴ Pa) for 100 minutes or 7 days and UV radiation. Induction of rifampicin-resistant mutants was observed with UV and longtime exposure to vacuum. We have analyzed sequence changes in rpoB gene of the mutants, and found that about a half of those obtained from vacuum exposure carried tandem-double base substitutions, the majority of which belonged to a single allele (r201) of CA to TT change. This demonstrates that the exposure to high vacuum causes forced dehydration in the vicinity of DNA, resulting in unique base-substitution mutations. [J Radiat Res 44:417 (2003)]