Evaluation of the role hydroxyl radicals and iron play in hydrogen peroxide killing of Xanthomonas campestris pv. phaseoli

Hydroxyl radical, a product of H2O2 metabolism in the Fenton reaction, is a major reactive oxygen species involved in H2O2 killing of Xanthomonas camp estris pv. phaseoii (Xp). Compounds which absorbed hydroxyl radicals protec ted Xanthomonas from H2O2 killing, but not from killing by a superoxide gen erator or an organic peroxide. Addition of iron potentiated H2O2 killing. O n the other hand, pre-treatment of Xp with an iron chelator showed no prote ctive effects and H2O2 killing was actually enhanced. Unexpectedly, resuspe nsion of Xp in either water or phosphate buffer induced high-level resistan ce to H2O2 killing. The unknown protection mechanism was independent of new protein synthesis. (C) 1998 Federation of European Microbiological Societi es. Published by Elsevier Science B.V. All rights reserved.