Unexpected chemoreceptors mediate energy taxis towards electron acceptors in Shewanella oneidensis

Authors

  • Claudine Baraquet,

    1. Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
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  • Laurence Théraulaz,

    1. Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
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  • Chantal Iobbi-Nivol,

    1. Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
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  • Vincent Méjean,

    1. Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
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  • Cécile Jourlin-Castelli

    Corresponding authorSearch for more papers by this author

*E-mail jourlin@ifr88.cnrs-mrs.fr; Tel. (+33) 4 91 16 40 32; Fax (+33) 4 91 71 89 14.

Summary

Shewanella oneidensis uses a wide range of terminal electron acceptors for respiration. In this study, we show that the chemotactic response of S. oneidensis to anaerobic electron acceptors requires functional electron transport systems. Deletion of the genes encoding dimethyl sulphoxide and trimethylamine N-oxide reductases, or inactivation of these molybdoenzymes as well as nitrate reductase by addition of tungstate, abolished electron acceptor taxis. Moreover, addition of nigericin prevented taxis towards trimethylamine N-oxide, dimethyl sulphoxide, nitrite, nitrate and fumarate, showing that this process depends on the ΔpH component of the proton motive force. These data, together with those concerning response to metals (Bencharit and Ward, 2005), support the idea that, in S. oneidensis, taxis towards electron acceptors is governed by an energy taxis mechanism. Surprisingly, energy taxis in S. oneidensis is not mediated by the PAS-containing chemoreceptors but rather by a chemoreceptor (SO2240) containing a Cache domain. Four other chemoreceptors also play a minor role in this process. These results indicate that energy taxis can be mediated by new types of chemoreceptors.

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