The ability of the human intestinal pathogen Campylobacter jejuni to respond to oxidative stress is central to bacterial survival both in vivo during
infection and in the environment. Re-annotation of the C. jejuni NCTC11168 genome revealed the presence of two MarR-type transcriptional regulators Cj1546 and Cj1556, originally annotated as hypothetical
proteins, which we have designated RrpA and RrpB (regulator of response to
peroxide) respectively. Previously we demonstrated a role for RrpB in both oxidative and aerobic (O2) stress and that RrpB was
a DNA binding protein with auto-regulatory activity, typical of MarR-type transcriptional regulators. In this study, we show that RrpA is also
a DNA binding protein and that a rrpA mutant in strain 11168H exhibits increased sensitivity to
hydrogen peroxide oxidative stress. Mutation of either rrpA or rrpB reduces
catalase (KatA) expression. However, a rrpAB double mutant exhibits higher levels of resistance to
hydrogen peroxide oxidative stress, with levels of KatA expression similar to the wild-type strain. Mutation of either rrpA or rrpB also results in a reduction in the level of katA expression, but this reduction was not observed in the rrpAB double mutant. Neither the rrpA nor rrpB mutant exhibits any significant difference in sensitivity to either
cumene hydroperoxide or
menadione oxidative stresses, but both mutants exhibit a reduced ability to survive aerobic (O2) stress, enhanced biofilm formation and reduced virulence in the Galleria mellonella
infection model. The rrpAB double mutant exhibits wild-type levels of biofilm formation and wild-type levels of virulence in the G mellonella
infection model. Together these data indicate a role for both RrpA and RrpB in the C. jejuni
peroxide oxidative and aerobic (O2) stress responses, enhancing bacterial survival in vivo and in the environment.