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Title: Copper chloride induces antioxidant gene expression but reduces ability to mediate H<inf>2</inf>O<inf>2</inf> toxicity in Xanthomonas campestris
Authors: Phornphan Sornchuer
Poommaree Namchaiw
Jarunee Kerdwong
Nisanart Charoenlap
Skorn Mongkolsuk
Paiboon Vattanaviboon
Environmental Health
Chulabhorn Research Institute
Mahidol University
Center of Excellence on Environmental Health and Toxicology
Keywords: Immunology and Microbiology
Issue Date: 1-Feb-2014
Citation: Microbiology (United Kingdom). Vol.160, No.PART 2 (2014), 458-466
Abstract: Copper (Cu)-based biocides are currently used as control measures for both fungal and bacterial diseases in agricultural fields. In this communication, we show that exposure of the bacterial plant pathogen Xanthomonas campestris to nonlethal concentrations of Cu2+ ions (75 μM) enhanced expression of genes in OxyR, OhrR and IscR regulons. High levels of catalase, Ohr peroxidase and superoxide dismutase diminished Cu2+-induced gene expression, suggesting that the production of hydrogen peroxide (H2O2) and organic hydroperoxides is responsible for Cu2+-induced gene expression. Despite high expression of antioxidant genes, the CuCl2-treated cells were more susceptible to H2O2 killing treatment than the uninduced cells. This phenotype arose from lowered catalase activity in the CuCl2-pretreated cells. Thus, exposure to a nonlethal dose of Cu2+ renders X. campestris vulnerable to H2O2, even when various genes for peroxide-metabolizing enzymes are highly expressed. Moreover, CuCl2-pretreated cells are sensitive to treatment with the redox cycling drug, menadione. No physiological cross-protection response was observed in CuCl2-treated cells in a subsequent challenge with killing concentrations of an organic hydroperoxide. As H2O2 production is an important initial plant immune response, defects in H2O2 protection are likely to reduce bacterial survival in plant hosts and enhance the usefulness of copper biocides in controlling bacterial pathogens. © 2014 SGM.
ISSN: 14652080
Appears in Collections:Scopus 2011-2015

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