Abrogation of SOS mutagenesis by the <i>E. coli</i> OxyR oxidative stress response

Many microorganisms such as pathogenic bacteria that attempt to invade a host will encounter a series of host-produced challenges that try to thwart their entry into and establishment within the host. As a countermeasure, the invading organisms have evolutionarily developed a range of stress responses that will help them to counter such challenges. The current study explores what happens in the bacterium <i>E. coli</i> when two such systems are induced simultaneously. We show that, remarkably, the strong increase in the mutation rate upon SOS induction (provoked by DNA replication stress) is nearly completely abolished by OxyR oxidative stress response. This study may serve as a paradigm for studies that might reveal novel regulatory features in cells subjected to multiple stressors.