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Mol Microbiol. 2009 Jul;73(2):278-90. doi: 10.1111/j.1365-2958.2009.06770.x. Epub 2009 Jun 23.

Unexpected chemoreceptors mediate energy taxis towards electron acceptors in Shewanella oneidensis.

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1
Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique, 13402 Marseille Cedex 20, France.

Abstract

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 DeltapH 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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