Generation of reactive oxygen species by lethal attacks from competing microbes

Significance How microbes respond to lethal attacks from competing species is not fully understood. Here, we investigated the response of Escherichia coli to attacks from the type VI secretion system (T6SS), bacteriophage P1 vir , and polymyxin B. We report that generation of reactive oxygen species (ROS) is a general outcome of potentially lethal activities mediated by contact-dependent or contact-independent interactions of aggressive competing bacterial species and phage. An ROS response gene, soxS , is highly induced in response to all sources of attacks tested. This discovery will likely prompt other investigations into why evolution has selected expression of this gene as a “first responder” to potentially lethal interspecies competition.