EFFECTS OF HEATING DRY BACTERIA AND SPORES ON THEIR PHENOTYPE AND GENOTYPE

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Abstract
Vegetative cells (Escherichia coli) or spores (Bacillus subtilis) in the dried state in vacuum were heated to 135[degree]C to 155[degree]C for 16 min. Under these conditions, the vegetative cells of E. coli were almost as resistant to heat as the spores of B. subtilis: however, the former differed from the latter by exhibiting the phenomenon of pseudoauxotrophy. Sufficient survival for determination of mutants was obtained; the mutant frequencies were 1 to 10% (lactose-; auxotrophs). Both stable and unstable mutants were obtained. The mutants of B. subtilis could be transformed by deoxyribonucleic acid from the wild strain. The implications of these findings have been discussed.