Ecological diversification in the Bacillus cereus Group

Authors

  • Marie-Hélène Guinebretière,

    Corresponding author
    1. Institut National de la Recherche Agronomique, UMR A408 Sécurité et Qualité des Produits d'Origine Végétale, INRA, Domaine Saint-Paul, Site Agroparc, F-84914 Avignon Cedex 9, France.
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  • Fabiano L. Thompson,

    1. Laboratory for Microbiology, and BCCM/LMG Bacteria Collection, Ghent University, Ghent 9000, Belgium.
    2. Federal University of Rio de Janeiro, Institute of Biology, Department of Genetics, Ilha do fundão, Caixa postal 68011, CEP 21944-970, Rio de Janeiro, Brazil.
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  • Alexei Sorokin,

    1. Institut National de la Recherche Agronomique, Laboratoire de Génétique Microbienne, Centre de Recherche de Jouy-en-Josas, 78352 Jouy-en-Josas cedex, France.
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  • Philippe Normand,

    1. Université Lyon 1, CNRS, UMR 5557, Ecologie Microbienne, Lyon, F-69003 Villeurbanne, France.
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  • Peter Dawyndt,

    1. Laboratory for Microbiology, and BCCM/LMG Bacteria Collection, Ghent University, Ghent 9000, Belgium.
    2. Department of Applied Mathematics and Computer Science, Ghent University, Krijgslaan 281, S9 B-9000 Ghent, Belgium.
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  • Monika Ehling-Schulz,

    1. Lehrstuhl für Mikrobielle Ökologie, Department für Grundlagen der Biowissenschaften, Technische Universität München, Weihenstephaner Berg 3, D-85354 Freising, Germany.
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  • Birgitta Svensson,

    1. Swedish Dairy Association, Scheelevaegen 18, 223 63 Lund, Sweden.
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  • Vincent Sanchis,

    1. Institut National de la Recherche Agronomique, Unité Génétique Microbienne et Environnement, INRA, La Minière, 78285 Guyancourt, Cedex, France.
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  • Christophe Nguyen-The,

    1. Institut National de la Recherche Agronomique, UMR A408 Sécurité et Qualité des Produits d'Origine Végétale, INRA, Domaine Saint-Paul, Site Agroparc, F-84914 Avignon Cedex 9, France.
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  • Marc Heyndrickx,

    1. Ministry of the Flemish Community, Center for Agricultural Research, Department of Animal Product Quality, Brusselsesteenweg 370, B-9090 Melle, Belgium.
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  • Paul De Vos

    1. Laboratory for Microbiology, and BCCM/LMG Bacteria Collection, Ghent University, Ghent 9000, Belgium.
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*E-mail guinebre@avignon.inra.fr; Tel. (+33) 432 7225 24; Fax (+33) 432 72 24 92.

Summary

The Bacillus cereus Group comprises organisms that are widely distributed in the environment and are of health and economic interest. We demonstrate an ‘ecotypic’ structure of populations in the B. cereus Group using (i) molecular data from Fluorescent Amplified Fragment Length Polymorphism patterns, ribosomal gene sequences, partial panC gene sequences, ‘psychrotolerant’ DNA sequence signatures and (ii) phenotypic and descriptive data from range of growth temperature, psychrotolerance and thermal niches. Seven major phylogenetic groups (I to VII) were thus identified, with ecological differences that provide evidence for a multiemergence of psychrotolerance in the B. cereus Group. A moderate thermotolerant group (VII) was basal to the mesophilic group I, from which in turn distinct thermal lineages have emerged, comprising two mesophilic groups (III, IV), an intermediate group (V) and two psychrotolerant groups (VI, II). This stepwise evolutionary transition toward psychrotolerance was particularly well illustrated by the relative abundance of the ‘psychrotolerant’rrs signature (as defined by Pruss et al.) copies accumulated in strains that varied according to the phylogenetic group. The ‘psychrotolerant’cspA signature (as defined by Francis et al.) was specific to group VI and provided a useful way to differentiate it from the psychrotolerant group II. This study illustrates how adaptation to novel environments by the modification of temperature tolerance limits has shaped historical patterns of global ecological diversification in the B. cereus Group. The implications for the taxonomy of this Group and for the human health risk are discussed.

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