Nitrous acid induced damage in T7 DNA and phage.

T7 phage was exposed to 56 mM nitrous acid at pH 4.6 causing a 90% decrease in survival for each 10 min duration of exposure. The survival of phage made by encapsulating nitrous acid treated DNA into empty phage heads was nearly the same as the survival of phage exposed to nitrous acid in vivo. In contrast to previous reports, growth of SOS-induced wild-type E.coli showed no increase in survival. The survival of nitrous acid treated phage was not lowered when grown on E.coli strains deficient in DNA polymerase I, exonuclease III, and the uvrA component of the nucleotide excision-repair endonuclease. Therefore, these enzymes are not vital for repair of nitrous acid induced damage in bacteriophage T7.