Microbial studies in the Biostack experiment of the Apollo 16 mission: germination and outgrowth of single Bacillus subtilis spores hit by cosmic HZE particles.

Bacillus subtilis spores were flown in the Biostack experiment aboard the Apollo 16 command module. The spores embedded in plastic foils were stacked between physical track detectors. The energy loss spectrum of the heavy particles of cosmic radiation was determined. Biological studies were restricted to the high-energy loss component of these particles. Spores that had received single hits whose positions were determined with a typical accuracy of +/- 1 micrometers, were investigated for radiation effects on germination and outgrowth. It was found that germination was not influenced by a hit by an HZE particle, but outgrowth was reduced significantly.