Lethal interaction between ultraviolet-violet radiations and methyl methane sulphonate in repair proficient and repair deficient strains of Escherichia coli

The lethal interaction between monochromatic radiation at various wavelengths and methyl methane sulphonate was tested in strains of Escherichia coli proficient and deficient in DNA repair. In the repair proficient wild-type strain K 12 AB 1157, the efficiency of sensitization to MMS as a function of dose (at 334nm, 365 nm and 405 nm) was found to be directly correlated with the dose necessary to remove the shoulder from the survival curve at the wavelength employed. The 365 nm:MMS interaction was also observed in other repair proficient E. coli strains (W3110 and B/r) but was absent in a recA and a polA strain. Pre-treatment of AB 1157 with MMS leads to a much larger interaction than pre-irradiation with 365 nm. It is concluded that dose-dependent damage to DNA repair by near-UV radiation is involved in the interaction and possibly that MMS causes irreversible damage to repair enzymes. (author)