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Preliminary description of biocidal (syringomycin) activity in fluorescent plant pathogenic Pseudomonas species
F P Hu1, J M Young, M J Fletcher
1Landcare Research, Auckland, New Zealand.
Abstract:
Strains representing the fluorescent plant pathogenic Pseudomonas spp., Ps. agarici, Ps. asplenii, Ps. avellanae, Ps. beteli, Ps. caricapapayae, Ps. cichorii, Ps. corrugata, Ps. ficuserectae, Ps. flectens, Ps. fuscovaginae, Ps. marginalis, Ps. meliae, Ps. savastanoi, Ps. syringae, Ps. tolaasii and Ps. viridiflava were tested for biocidal activity using Aspergillus niger as assay organism. Inhibitory behaviour was found in strains of Ps. asplenii, Ps. blatchfordae, Ps. cichorii, Ps. corrugata, Ps. fuscovaginae, Ps. marginalis, Ps. marginalis pv. pastinacea, Ps. syringae pv. syringae, Ps. syringae pv. aptata, Ps. syringae pv. atrofaciens, Ps. syringae pv. lapsa, Ps. tolaasii, and strains of a Pseudomonas sp. pathogenic to Actinidia, in the Ps. savastanoi genomic sp. Antifungal activity could be identified with the production of members of the syringomycin family of toxins by strains in Ps. syringae, Ps. asplenii and Ps. fuscovaginae. These toxin reactions support suggestions made elsewhere of the synonym of the latter two species. In a preliminary characterization using tests for stability to heat, protease, acid and alkaline treatments, unknown toxins consistent with syringomycin-like toxins the strains from Actinidia species. The toxins from Ps. cichorii and from Ps. corrugata differed in their reactions from all other agents. Pseudomonas tolaasii produces the antifungal compound tolaasin. The white line reaction with Ps. reactions, a test for tolaasin production by strains of Ps. tolaasii, was confirmed as specific for this compound. Some of these low molecular weight toxins may be produced by some of these plant pathogenic strains.
Insights
Certain Pseudomonas species exhibit antifungal properties by producing toxins like syringomycin and tolaasin. This study identifies specific strains with biocidal activity against Aspergillus niger, contributing to understanding plant pathogen interactions.
Area of Science:
- Microbiology
- Plant Pathology
- Biochemistry
Background:
- Plant pathogenic Pseudomonas species are a diverse group affecting various crops.
- Understanding their biocidal mechanisms is crucial for disease management.
- Previous research has hinted at toxin production by some Pseudomonas strains.
Purpose of the Study:
- To assess the biocidal activity of fluorescent plant pathogenic Pseudomonas species against Aspergillus niger.
- To identify specific Pseudomonas strains producing antifungal toxins.
- To characterize the nature of these toxins and their potential taxonomic implications.
Main Methods:
- Testing a range of fluorescent plant pathogenic Pseudomonas strains for inhibitory activity against Aspergillus niger.
- Identifying toxin production, specifically syringomycin family toxins and tolaasin.
- Preliminary characterization of toxin stability under various treatments (heat, protease, acid, alkaline).
Main Results:
- Inhibitory activity was observed in strains of Pseudomonas asplenii, Pseudomonas blatchfordae, Pseudomonas cichorii, Pseudomonas corrugata, Pseudomonas fuscovaginae, Pseudomonas marginalis, Pseudomonas tolaasii, and specific Pseudomonas syringae pathovars.
- Antifungal activity was linked to syringomycin-like toxins in Ps. syringae, Ps. asplenii, and Ps. fuscovaginae.
- Pseudomonas tolaasii was confirmed to produce the antifungal compound tolaasin, with the white line reaction being a specific test.
Conclusions:
- Several fluorescent plant pathogenic Pseudomonas species possess significant biocidal activity against Aspergillus niger.
- The production of syringomycin-like toxins by Ps. syringae, Ps. asplenii, and Ps. fuscovaginae supports their potential synonymy.
- Pseudomonas cichorii and Pseudomonas corrugata produce distinct toxins, while tolaasin is specific to Pseudomonas tolaasii.