Ohr plays a central role in bacterial responses against fatty acid hydroperoxides and peroxynitrite

Significance Hydroperoxides play central roles in cell signaling. Hydroperoxides of arachidonic acid are mediators of inflammatory processes in mammals, whereas hydroperoxides of linoleic acid play equivalent roles in plants. Peroxynitrite is also involved in host–pathogen interactions, and hydroperoxide levels must therefore be strictly controlled by host-derived thiol-dependent peroxidases. Organic hydroperoxide resistance (Ohr) enzymes, which are present in many bacteria, display unique biochemical properties, reducing fatty acid hydroperoxides and peroxynitrite with extraordinary efficiency. Furthermore, Ohr (but not other thiol-dependent peroxidases) is involved in the Pseudomonas aeruginosa response to fatty acid hydroperoxides and to peroxynitrite, although the latter is more complex, probably depending on other enzymes. Therefore, Ohr plays central roles in the bacterial response to two hydroperoxides that are at the host–pathogen interface.