OxyR is required for oxidative stress resistance of the entomopathogenic bacterium and has a minor role during the bacterial interaction with its hosts.

is a Gram-negative bacterium, mutualistically associated with the soil nematode , and this nemato-bacterial complex is parasitic for a broad spectrum of insects. The transcriptional regulator OxyR is widely conserved in bacteria and activates the transcription of a set of genes that influence cellular defence against oxidative stress. It is also involved in the virulence of several bacterial pathogens. The aim of this study was to identify the OxyR regulon and investigate its role in the bacterial life cycle. An mutant was constructed in and phenotypically characterized and after reassociation with its nematode partner. OxyR plays a major role during the resistance to oxidative stress . Transcriptome analysis allowed the identification of 59 genes differentially regulated in the mutant compared to the parental strain. , the mutant was able to reassociate with the nematode as efficiently as the control strain. These nemato-bacterial complexes harbouring the mutant symbiont were able to rapidly kill the insect larvae in less than 48 h after infestation, suggesting that factors other than OxyR could also allow to cope with oxidative stress encountered during this phase of infection in insect. The significantly increased number of offspring of the nemato-bacterial complex when reassociated with the mutant compared to the control strain revealed a potential role of OxyR during this symbiotic stage of the bacterial life cycle.