The osmotic stress induced protein (OsmC) and organic hydroperoxide resistance protein (Ohr) were two antioxidant enzymes which play an important role in bacteria defensing organic or inorganic peroxidation. The osmC gene (DR_1538) and ohr gene (DR_1857) of Deinococcus radiodurans (D. radiodurans R1) encoded the two antioxidant enzymes in the OsmC superfamily. Fusion PCR of three sections in vitro and linear transformation method were used to firstly construct the spectinomycin-resistant mutant

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... stain (ΔosmC) and the kanamycin-resistant mutant strain (Δohr). The ΔosmC, Δohr mutants strain and wild-type strain were treated with CHP (cumene hydroperoxide), H 2 O 2 and NaCl stress treatments. The result showed that ΔosmC mutant is extremely sensitive to H 2 O 2 compared with the wild type, while Δohr mutant is more sensitive to CHP and the two mutant strains had no changes after NaCl stress. QRT-PCR results displayed that the osmC gene of the wild-type strain were up-regulated in both H 2 O 2 and NaCl stress treatments, and the osmC gene in H 2 O 2 stress levels was significantly upregulated. The ohr genes in wild-type strain after CHP and NaCl stress treatments upregulated approximately 2-folds. From above, it was presumed that there may be different at the preference of two peroxidases in OsmC superfamily selecting substrates and the mode of those interacting with their substrate; OsmC proteins may mainly use inorganic peroxide as its substrate and Ohr protein may be primarily based on the organic peroxide as its substrate.