A comparison of chemically defined and complex media for the production of Bacillus subtilis spores having reproducible resistance and germination characteristics.

Spores of Bacillus subtilis were produced on five batches of Antibiotic Assay Medium No. 1 obtained from different suppliers, five batches obtained from a single supplier and five batches of a chemically defined liquid medium. The magnitude of the variation within each of the three groups was compared in terms of heat resistance, glutaraldehyde resistance, germination rate and sensitivity of germinated spores to neomycin. For all these parameters the degree of reproducibility achieved by using a chemically defined liquid medium was substantially better than that using batches of complex medium from a single supplier. Even larger variations in these parameters resulted when different suppliers were used. The value of defined media for the production of spore inocula to be used in sterilization control and similar procedures is discussed.