Escherichia coli mutants lacking exonuclease III (xthA) are exceptionally sensitive to hydrogen peroxide. They are killed by H2O2 at 20 times the rate of wild-type bacteria and at 3 to 4 times the rate of recA cells. This is the first clear phenotypic sensitivity reported for xth- E. coli and should aid in clarifying peroxide-induced lethality and the in vivo role of exonuclease III.
