Role of single-strand DNA 3'-5' exonuclease ExoI and nuclease SbcCD in stationary-phase mutation in Escherichia coli K-12.

In RecBCD(+) cells, a mutated single-strand DNA 3'-5' exonuclease ExoI (SbcB15) induced an increase in stationary-phase mutation. In sbcB15 cells, as in wild-type cells, these mutations partially required RecA, RecB, RecF, and expression of the LexA regulon. The absence of nuclease SbcCD in sbcB15 cells decreased stationary-phase mutation and induced an increase in the number of cell filaments. The absence of ExoI (Deltaxon) in wild-type or sbcC cells did not change significantly the stationary-phase mutation. Differences between the sbcB15 and DeltaxonA cells suggest a correlation between level of SOS induction and the generation of stationary-phase mutations.