Molecular Mechanism of Radiation Resistance and Recovery of Bacterial Spores.
Final rept. 1 Apr 75-31 Mar 78,
ILLINOIS INST OF TECH CHICAGO
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Direct rejoining of DNA by ligase occurs in dormant spores in a radiation resistant strain but not in a radiation sensitive strain. The ability to rejoin DNA seems to be responsible for the extensive shoulder in the radiation survival curves, as well as for salt tolerance of a particular strain. Calcium form spores have increased resistance as well as increased water binding capacity. This seems to be due to the ability of calcium to convert weak cationic exchange groups in the spore such as R-COO- into strong anionic exchange groups such as R-COO-Ca 5H2O. Freeze-thawing causes DNA breakage in E. coli this seems to be the mechanism of cell death if breaks are not repaired. Mild heat triggers DNA breakage in E. coli the enzyme apurinic acid endonuclease in the E. coli cell is implicated in producing the breaks. These breaks may or may not be reversed by DNA ligase, thus resulting in survival or death of the cells, respectively. Author