Glycogen phosphorylase is involved in stress endurance and biofilm formation in Azospirillum brasilense Sp7

Authors

  • Anat Lerner,

    1. Department of Plant Pathology and Microbiology, The Otto Warburg Minerva Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
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  • Susana Castro-Sowinski,

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

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

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

    1. Department of Plant Pathology and Microbiology, The Otto Warburg Minerva Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
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  • Editor: Juan Imperial

Correspondence: Saul Burdman, Department of Plant Pathology and Microbiology, The Otto Warburg Minerva Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel. Tel.: +972 8 948 9369; fax: +972 8 946 6794; e-mail: saulb@agri.huji.ac.il

Abstract

Here we report the identification of a glycogen phosphorylase (glgP) gene in the plant growth-promoting rhizobacterium Azospirillum brasilense, Sp7, and the characterization of a glgP marker exchange mutant of this strain. The glgP mutant showed a twofold reduction of glycogen phosphorylase activity and an increased glycogen accumulation as compared with wild-type Sp7, indicating that the identified gene indeed encodes a protein with glycogen phosphorylase activity. Interestingly, the glgP mutant had higher survival rates than the wild type after exposure to starvation, desiccation and osmotic pressure. The mutant was shown to be compromised in its biofilm formation ability. Analysis of the exopolysaccharide sugar composition of the glgP mutant revealed a decrease in the amount of glucose, accompanied by increases in rhamnose, fucose and ribose, as compared with the Sp7 exopolysaccharide. To the best of our knowledge, this is the first study that demonstrates GlgP activity in A. brasilense, and shows that glycogen accumulation may play an important role in the stress endurance of this bacterium.

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