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Mucoid Mutants of the Biocontrol Strain Pseudomonas fluorescens CHA0 Show Increased Ability in Biofilm Formation on Mycorrhizal and Nonmycorrhizal Carrot Roots

February 2001 , Volume 14 , Number  2
Pages  255 - 260

Valeria Bianciotto , 1 Silvia Andreotti , 2 Raffaella Balestrini , 1 Paola Bonfante , 1 , 2 and Silvia Perotto 1

1Centro di Studio sulla Micologia del Terreno-C.N.R.; 2Dipartimento di Biologia Vegetale dell'Università, V.le Mattioli 25, 10125 Torino, Italy

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Accepted 25 October 2000.

Extracellular polysaccharides play an important role in the formation of bacterial biofilms. We tested the biofilmforming ability of two mutant strains with increased production of acidic extracellular polysaccharides compared with the wild-type biocontrol strain Pseudomonas fluorescens CHA0. The anchoring of bacteria to axenic nonmycorrhizal and mycorrhizal roots as well as on extraradical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices was investigated. The nonmucoid wild-type strain P. fluorescens CHA0 adhered very little on all surfaces, whereas both mucoid strains formed a dense and patchy bacterial layer on the roots and fungal structures. Increased adhesive properties of plant-growth-promoting bacteria may lead to more stable interactions in mixed inocula and the rhizosphere.

Additional keywords: alginate, PGPRs, pseudomonads, surface polysaccharides.

© 2001 The American Phytopathological Society