The chemotaxis-like Che1 pathway has an indirect role in adhesive cell properties of Azospirillum brasilense

Authors

  • Piro Siuti,

    1. Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
    2. Graduate School of Genome Science and Technology, Oak Ridge National Laboratory, University of Tennessee, Knoxville, TN, USA
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  • Calvin Green,

    1. Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, USA
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  • Amanda Nicole Edwards,

    1. Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
    2. Graduate School of Genome Science and Technology, Oak Ridge National Laboratory, University of Tennessee, Knoxville, TN, USA
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  • Mitchel J. Doktycz,

    1. Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
    2. Graduate School of Genome Science and Technology, Oak Ridge National Laboratory, University of Tennessee, Knoxville, TN, USA
    3. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA
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  • Gladys Alexandre

    Corresponding author
    1. Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, USA
    • Graduate School of Genome Science and Technology, Oak Ridge National Laboratory, University of Tennessee, Knoxville, TN, USA
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Correspondence: Gladys Alexandre, Department of Biochemistry, Cellular and Molecular Biology, F425 Walters Life Sciences Building, 1414 W. Cumberland Avenue, Knoxville, TN 37996, USA. Tel.: +1 865 974 0866; fax: +1 865 974 6306; e-mail: galexan2@utk.edu

Abstract

The Azospirillum brasilense chemotaxis-like Che1 signal transduction pathway was recently shown to modulate changes in adhesive cell surface properties that, in turn, affect cell-to-cell aggregation and flocculation behaviors rather than flagellar-mediated chemotaxis. Attachment to surfaces and root colonization may be functions related to flocculation. Here, the conditions under which A. brasilense wild-type Sp7 and che1 mutant strains attach to abiotic and biotic surfaces were examined using in vitro attachment and biofilm assays combined with atomic force microscopy and confocal microscopy. The nitrogen source available for growth is found to be a major modulator of surface attachment by A. brasilense and could be promoted in vitro by lectins, suggesting that it depends on interaction with surface-exposed residues within the extracellular matrix of cells. However, Che1-dependent signaling is shown to contribute indirectly to surface attachment, indicating that distinct mechanisms are likely underlying flocculation and attachment to surfaces in A. brasilense.

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