A Neisseria gonorrhoeae catalase mutant is more sensitive to hydrogen peroxide and paraquat, an inducer of toxic oxygen radicals

Catalase is hypothesized to be critical in the protection of Neisseria gonorrhoeae from H₂O₂ produced during aerobic respiration and by phagocytes during infection. Here we cloned the catalase (kat) gene of gonococcal strain FA1090 and constructed a genetically defined N. gonorrhoeae kat mutant to assess the role of catalase in defense against oxidative stress. The gonococcal kat gene conferred increased H₂O₂ resistance to a catalase-deficient Escherichia coli strain. Mutation of the kat gene in strain FA1090 via an in-frame deletion resulted in increased sensitivity to H₂O₂ and paraquat, an inducer of toxic oxygen radicals. Expression of catalase in trans from a shuttle vector restored catalase activity and paraquat resistance to the kat mutant, but not resistance to H₂O₂. The inability to fully complement the mutant was perhaps due to a modification in the catalase, as evidenced by altered mobility of the recombinant catalase on activity gels when expressed from the shuttle vector in N. gonorrhoeae. Additionally, we showed a 262 base pair region upstream of the kat gene is required for expression in E. coli and a putative fumarate-nitrate regulator (FNR) binding site is located in this region.