Phenotypic variation in Azospirillum brasilense exposed to starvation

Authors

  • Anat Lerner,

    1. Department of Plant Pathology and Microbiology, and The Otto Warburg Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
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  • Angel Valverde,

    1. Department of Plant Pathology and Microbiology, and The Otto Warburg Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
    2. Instituto de Recursos Naturales y Agrobiología de Salamanca, Consejo Superior de Investigaciones Científicas (IRNASA-CSIC), Salamanca, Spain.
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  • Susana Castro-Sowinski,

    1. Department of Plant Pathology and Microbiology, and The Otto Warburg Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
    2. Sección Bioquímica, Facultad de Ciencias, Universidad de la República y Unidad de Microbiología Molecular, Instituto Clemente Estable, Av. Igua 4225, Montevideo, Uruguay.
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  • Hadas Lerner,

    1. Department of Plant Pathology and Microbiology, and The Otto Warburg Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
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  • Yaacov Okon,

    1. Department of Plant Pathology and Microbiology, and The Otto Warburg Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
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  • Saul Burdman

    Corresponding author
    1. Department of Plant Pathology and Microbiology, and The Otto Warburg Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
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E-mail saulb@agri.huji.ac.il; Tel. (+972) 8 9489369; Fax (+972) 8 9466794.

Summary

Bacteria have developed mechanisms that allow them maintaining cell viability during starvation and resuming growth when nutrients become available. Among these mechanisms are adaptive mutations and phase variation, which are often associated with DNA rearrangements. Azospirillum brasilense is a Gram-negative, nitrogen-fixing, plant growth-promoting rhizobacterium. Here we report phenotypic variants of A. brasilense that were collected after exposure to prolonged starvation or after re-isolation from maize roots. The variants differed in several features from the parental strains, including pigmentation, aggregation ability, EPS amount and composition and LPS structure. One of the phenotypic variants, overproducing EPS and showing an altered LPS structure, was further characterized and showed differential response to several stresses and antibiotics relative to its parental strain. Characterization of the variants by repetitive-PCR revealed that phenotypic variation was often associated with DNA rearrangements.

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