Aer is a bidirectional redox sensor mediating negative chemotaxis to antibiotic-induced ROS in <i>Escherichia coli</i>

Motile bacteria rely on aerotaxis to seek environments that maximize energy production. We show that in <i>Escherichia coli</i>, Aer mediates not only positive chemotaxis toward favorable redox conditions but also negative chemotaxis in response to unfavorable ones, actively moving away from oxidizing environments, including reactive oxygen species (ROS)-generating antibiotics, a previously unrecognized behavioral mechanism for bacterial survival under oxidative stress. The ability of Aer to detect both oxidizing and reducing cellular environments reveals an unexpected sensory versatility, shared to varying degrees by other <i>E. coli</i> chemoreceptors.