Study of the implication of reactive oxygen species in Caulobacter crescentus copper-induced negative chemotaxis system

  • Thomas Lamot

    Student thesis: Master typesMaster in biochemistry and molecular and cell biology Research focus


    Copper is a heavy metal which is well-known to be toxic at high doses for most organisms. Recently, an original defense strategy has been described in the dimorphic bacteria Caulobacter crescentus when exposed to copper stress. Whereas the stalked cells expel copper from their cytoplasm, the swarmer cells accumulate copper and engage readily a flight response to find a copper-free environment. This flight response is likely mediated by a chemotaxis system. However, as copper is known to induce oxidative stress in vitro, it is not clear whether the cues sensed by the chemoreceptors are either copper or copper-induced reactive oxygen species.
    The first part of this study aimed to determine whether copper is able to impact the redox balance of C. crescentus by generating reactive oxygen species. Using a redox-sensitive YFP as a reporter of the in vivo glutathione redox state, fluorometry analysis and fluorescence microscopy showed that copper is able to shift the normal oxidized/reduced glutathione equilibrium toward oxidized glutathione.
    On the second part, chemotaxis of KO mutants of candidate genes for copper sensing was tested toward H2O2 and paraquat dichloride. Interestingly, some candidates for O2 sensing were also described. Finally, a KO mutant of yaaA, a protein thought to be involved in H2O2 resistance, was found to display an increased H2O2 flight.
    Date of Award17 Jan 2019
    Original languageEnglish
    Awarding Institution
    • University of Namur
    SupervisorJean-Yves Matroule (Jury)

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