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• The BNP PARIBAS Foundation

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We thank Claude Lebos, Gérard Prensier and, most of all, Brigitte Arbeille for their skillfull preparation of SEM and TEM micrographs of bacterial biofilms at  Laboratoire de Biologie Cellulaire et Microscopie Electronique, UFR Médecine, 37032 TOURS cedex, France