Crucial traits ensuring survival and activity of the biocontrol agent Pseudomonas fluorescens CHA0

• Unité de recherche: COST
• Numéro de projet: C99.0032
• Titre du projet anglais: Crucial traits ensuring survival and activity of the biocontrol agent Pseudomonas fluorescens CHA0

Mots-clé (Anglais)

Pseudomonas; environmental stress; sigma factors; survival; soil; formulation; biocontrol; antifungal compound; plant diseases

Programme de recherche (Anglais)

COST-Action 830 - Microbial inoculants in agriculture and the environment

Description succincte (Anglais)

See abstract

Autres indications (Anglais)

Full name of research-institution/enterprise: Université de Lausanne Institut de Microbiologie Fondamentale

Partenaires et organisations internationales (Anglais)

B, DK, FIN, F, D, GR, H, I, NL, N, PL, P, E, S, CH, GB

Résumé des résultats (Abstract) (Anglais)

The root-colonising bacterium Pseudomonas fluorescens can be used to control root diseases of crops caused by soilborne pathogenic fungi. Numerous environmental stress conditions such as hyperosmolarity and desiccation affect the persistence and biological activity of this plant-beneficial microorganism after formulation and addition to soil. In a first part of our project, we have focused on the relative contributions of the alternative sigma factors AlgU (= RpoE), RpoS, and RpoN to the regulation of stress response and biocontrol activity in P. fluorescens. AlgU was found to be essential for adaptation to dry stress, whereas all three sigma factors were required for tolerance to osmotic stress induced by high salt or sugar concentrations. In addition, RpoN and RpoS were key regulatory elements controlling expression levels of antifungal compounds and biocontrol activity in P. fluorescens. Somewhat unexpectedly, overexpression of either sigma factor in P. fluorescens did not result in enhanced stress tolerance or biocontrol ability. For instance, enhanced exopolysaccharide production induced by AlgU overexpression did not improve the capacity of P. fluorescens to withstand adverse environmental conditions and even reduced its biocontrol efficacy. Our future experiments will aim at a better understanding of the crosstalk between RpoN, RpoS and AlgU to see how changes in the balance among these sigma factors affect stress response and biocontrol activity in P. fluorescens. In a second part of the project, a number of molecular approaches have been taken to enhance the biocontrol activity of P. fluorescens by overexpressing the potent antifungal compound dihydroaeruginoate. Further work will be necessary to achieve stable high-level production of this compound.

Références bases de données (Anglais)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C99.0032