Summary
Cell division and incorporation of 3H-thymidine into acid-insoluble fraction were investigated for three uvrA recA double mutants of E. coli K12 irradiated with UV at 1.5 ergs/mm2, producing about ten pyrimidine dimers per genome (about 0.01% survival). Cell division was measured both in M9 medium and in the same medium which was made very viscous by the addition of Metlose (the same product as Methocel used by Lin et al., 1971). It was found that a major fraction of irradiated bacteria continues to divide once or twice and stops thereafter. Incorporation of 3H-thymidine proceeded at a considerable rate for a short period following irradiation and then stopped. During subsequent incubation, the incorporation gradually decreased and after 4 h incubation most of the early incorporated radioactivity disappeared from the acid-insoluble fraction. These results indicate that cell division occurs after irradiation without parallel DNA synthesis as in a recA thy mutant of E. coli K12 deprived of thymine (Inouye, 1971). These results suggest that UV irradiation increases lethal sectoring due to the “reckless” cell division without parallel DNA synthesis. Since DNA synthesis took place only for a short period after irradiation, it may be assumed that the recA gene normally has at least a dual function; 1. elimination of damage induced by UV to support elongation or initiation of DNA, and 2. maintenance of coordination between DNA synthesis and cell division.
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Suzuki, K. Cell division and DNA synthesis in uvrA recA double mutants of E. coli K12. Molec. Gen. Genet. 129, 249–258 (1974). https://doi.org/10.1007/BF00267917
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DOI: https://doi.org/10.1007/BF00267917