Studies on the Radioresistance of Bacillus Spores

Radioresistance of the spores of 46 strains of Bacillus was determined based on their dose-survival curves. The spores were produced on three kinds of sporulating medium.

The variations in the radioresistance among species and strains were found, and also the radioresistance of spores depended upon the sporulating medium. The shapes of dose-survival curves are closely associated with the taxonomical groups of the genus Bacillus.

Radioresistance of the spores showed no apparent correlation to their contents of dipicolinic acid, calcium and magnesium, but a slight correlation was observed between radioresistance and the molar ratio of Ca to DPA or Mg to Ca. Radioresistance of the spores in some groups correlated to their GC content, but no correlation was found in the other species. There was no correlation between heat resistance and radioresistance.