In a new study appearing in PNAS this week, Brandeis Molecular and Cell Biology graduate student Houra Merrikh and co-workers from the Lovett lab identified the E.coli gene iraD as a regulator of the response to oxidative DNA damage in exponentially growing bacteria. Interestingly, the mechanism seems to involve the alternative RNA polymerase sigma factor RpoS, previously characterized as a regulator of expression during the “stationary phase”. Merrikh et al. argue that this response works in parallel with the previously characterized SOS response in protecting growing bacteria from DNA damage.