Unusual extracellular appendages deployed by the model strain Pseudomonas fluorescens C7R12

Dorian Bergeau (1) , Sylvie Mazurier (2) , Corinne Barbey (1) , Annabelle Mérieau (1) , Andrea Chane (1) , Didier Goux (3) , Sophie Bernard (4, 5) , Azeddine Driouich (4) , Philippe Lemanceau (2) , Maïté Vicré (4) , Xavier Latour (1)

1 LMSM - Laboratoire de Microbiologie Signaux et Microenvironnement
2 Agroécologie [Dijon]
3 ICORE - Interactions Cellules Organismes Environnement
4 Glyco-MEV - Laboratoire de Glycobiologie et Matrice Extracellulaire Végétale
5 PRIMACEN - Plate-Forme de Recherche en Imagerie Cellulaire de Haute-Normandie

Pseudomonas fluorescens is considered to be a typical plant-associated saprophytic bacterium with no pathogenic potential. Indeed, some P. fluorescens strains are well-known rhizo-bacteria that promote plant growth by direct stimulation, by preventing the deleterious effects of pathogens, or both. Pseudomonas fluorescens C7R12 is a rhizosphere-competent strain that is effective as a biocontrol agent and promotes plant growth and arbuscular mycorrhization. This strain has been studied in detail, but no visual evidence has ever been obtained for extracellular structures potentially involved in its remarkable fitness and biocon-trol performances. On transmission electron microscopy of negatively stained C7R12 cells, we observed the following appendages: multiple polar flagella, an inducible putative type three secretion system typical of phytopathogenic Pseudomonas syringae strains and densely bundled fimbria-like appendages forming a broad fractal-like dendritic network around single cells and microcolonies. The deployment of one or other of these elements on the bacterial surface depends on the composition and affinity for the water of the microenvi-ronment. The existence, within this single strain, of machineries known to be involved in motility, chemotaxis, hypersensitive response, cellular adhesion and biofilm formation, may partly explain the strong interactions of strain C7R12 with plants and associated microflora in addition to the type three secretion system previously shown to be implied in mycorrhizae promotion.

Keywords: syringae pv. tomato; hrp pilus; nonspecific adherence; biological-control; gene-expression; fe-pyoverdine

Keywords: iii secretion system; actinobacillus-actinomycetemcomitans; population-dynamics; iron acquisition

Domains: Life Sciences [q-bio]; Vegetal Biology; Life Sciences [q-bio]; Biotechnology; Life Sciences [q-bio]; Vegetal Biology; Phytopathology and phytopharmacy; Life Sciences [q-bio]; Vegetal Biology; Plant breeding; Life Sciences [q-bio]; Biochemistry, Molecular Biology; Molecular biology; Life Sciences [q-bio]; Cellular Biology; Life Sciences [q-bio]; Biochemistry, Molecular Biology; Biochemistry [q-bio.BM]; Life Sciences [q-bio]; Development Biology; Life Sciences [q-bio]; Cellular Biology; Cell Behavior [q-bio.CB]; Life Sciences [q-bio]; Cellular Biology; Subcellular Processes [q-bio.SC]; Life Sciences [q-bio]; Biochemistry, Molecular Biology; Genomics [q-bio.GN]

Dorian Bergeau, Sylvie Mazurier, Corinne Barbey, Annabelle Mérieau, Andrea Chane, et al.. Unusual extracellular appendages deployed by the model strain Pseudomonas fluorescens C7R12. PLoS ONE, 2019, 14 (8), pp.e0221025. ⟨10.1371/journal.pone.0221025⟩. ⟨hal-02276826⟩