Repair of the double-strand breaks produced by 125I disintegrations in the DNA of Micrococcus radiodurans.

Abstract

Wild-type M. radiodurans and two radiosensitive mutants were used to study the lethal effects of 125I disintegrations in their DNA. The relative sensitivities of these three strains to inactivation by gamma-radiation were reflected in their relative sensitivities to inactivation by 125I decay. The number of double-strand (ds) breaks in the DNA appeared to be similar at levels of gamma-radiation and of 125I decay that reduced survival to 10%. All three strains of M. radiodurans rapidly repaired ds breaks produced in their DNA by either gamma-radiation or 125I disintegrations. If one ds break per is a lethal event [Kirsch et al., 1975], cells of the three strains tested would die only when they had left unrepaired one ds break out of an initial 45,600 or 1800 ds breaks per single cell.