Modulation of peroxide stress response by thiol reagents and the role of aredox sensor-transcription regulator, OxyR in mediating the response in Xanthomonas

Pretreatment of Xanthomonas campestris pv. phaseoli with low inducing conce ntrations of thiol reagents such as N-ethylmaleimide (NEM) and diamide indu ced resistance to H2O2 killing. In addition, these compounds were moderate inducers of peroxide detoxification enzymes such as catalase and alkyl hydr operoxide reductase. For both cases, thiol reagent induced responses requir ed a functional redox sensor/transcription activator oxyR and were absent i n an oxyR mutant. By contrast, NEM pretreatment enhanced the killing effect s of organic peroxide. The observed Xanthomonas physiological responses to thiol reagent pretreatment, and subsequent challenge with peroxide stress, differed from other bacteria. (C) 1999 Federation of European Microbiologic al Societies. Published by Elsevier Science B.V. All rights reserved.