Microbial Response to Spaceflight Conditions

Abstract

Space radiation, including Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE), represents a major hazard for biological systems beyond Earth. Spores of Bacillus subtilis have been shown to be suitable dosimeters for probing extreme terrestrial and extraterrestrial environmental conditions in astrobiological and environmental studies. During dormancy spores are metabolically inactive; thus substantial DNA, protein, tRNA and ribosome damage can accumulate while the spores are incapable of repairing and/or degrading damaged DNA and proteins. We used different genotypes of B. subtilis to study the effects of extraterrestrial conditions in both space and ground-based experiments. Spore survival was strongly dependent on the functionality of all of the structural components, with small acid-soluble spore proteins, coat layers, and dipicolinic acid (DPA) and the interaction of several DNA repair mechanisms. I will present results from physiological and genetic studies regarding spore resistance to spaceflight conditions as well as data from the transcriptome analyses of germinating B. subtilis spores. Our ultimate goal is to obtain a complete model describing spore persistence and longevity in high radiation-exposed environments, with implications for future life detection missions and human spaceflight.