Vacuum-induced Mutations In Bacillus Subtilis Spores
Abstract
During irradiation experiments with vacuum-UV radiation using synchrotron sources, we made unexpected observation that Bacillus subtilis spores of several recombination-deficient strains lost colony-forming ability by the exposure to high vacuum alone. Since this suggested the possible injury in spore DNA, we looked for mutation induction using the spores of strains HA101 (wild-type repair capability) and TKJ6312 (excision and spore repair deficient) that did not lose survivability. It was found that the frequency of nalidixic-acid resistant mutation increased several times in both of these strains by the exposure to high vacuum (10e-4 Pa after 24 hours). The analysis of sequence changes in gyrA gene showed that the majority of mutations carried a unique allele (gyrA12) of tandem double-base substitutions from CA to TT. The observation has been extended to rifampicin resistant mutations, the majority of that carried substitutions from CA to TT or AT in rpoB gene. On the other hand, when the spores of strains PS578 and PS2319 (obtained from P. Setlow) that are defective in a group of small acidic proteins (alpha/beta-type SASP) were similarly treated, none of the mutants analyzed carried such changes. This suggests that the unique mutations might be induced by the interaction of small acidic proteins with spore DNA under forced dehydration. The results indicate that extreme vacuum causes severe damage in spore DNA, and provide additional constraint to the long-term survival of bacterial spores in the space environment.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.2047M