Flavobacterium meningosepticum produced a peroxidase coordinately with a H2O2-forming nucleoside oxidase under culture conditions where the bacterium inducibly produced the nucleoside oxidase. The nucleoside oxidase and peroxidase both required Fe2+ or Fe3+ for their production, and Cu2+ enhanced the production of both enzymes. The addition of nucleoside analogs to the medium also enhanced the production of both enzymes. The time course of peroxidase production coincided with that of the nucleoside oxidase production. These results suggest that the peroxidase has a specific function related to the nucleoside oxidase reaction, in breaking down the H2O2 formed, which would otherwise cause oxidative cell damage. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.