The Relationship of Sulfhydryl and Disulfide Constituents of Bacillus cereus to Radioresistance

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Abstract
Sulfhydryl (SH) and disulf ide (SS) levels in vegetative cells and spores of B. cereus were studied to explain the biochemical basis for increased radioresistance of mature spores. Insight has been gained by the use of an organic sulfur-requiring auxotrophic mutant. The determination of SH and SS was carried out on intact organisms polarographically by estimation of unreacted MeHgI, a reagent specific for SH groups. This reagent was made accessible to cells by treating them for 24 hours in the presence of 8 [image] urea. Results of various analyses of the wild-type strains agreed with published findings,, that radio-resistance increased with progressive spore maturity, and that spores had extremely low, or no, SH content Mutant spores did not reflect a progressive radioresistance with maturation. In addition, it was noted that, when the mutant was grown on 3 different levels of cystine or cysteine, spores with greatest radioresistance were formed on highest amino acid concentration. However, this work failed to establish a direct relationship between disulfide content and radioresistance. Instead it was found that an increased SS/SH ratio accompanied the development of radioresistance in any cell sample.