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7‐hydroxytropolone is the main metabolite responsible for the fungal antagonism of Pseudomonas donghuensis strain SVBP6.

Authors :
Muzio, Federico M.
Agaras, Betina C.
Masi, Marco
Tuzi, Angela
Evidente, Antonio
Valverde, Claudio
Source :
Environmental Microbiology; Jul2020, Vol. 22 Issue 7, p2550-2563, 14p
Publication Year :
2020

Abstract

Summary: Pseudomonas donghuensis strain SVBP6, an isolate from an agricultural plot in Argentina, displays a broad‐spectrum and diffusible antifungal activity, which requires a functional gacS gene but could not be ascribed yet to known secondary metabolites typical of Pseudomonas biocontrol species. Here, we report that Tn5 mutagenesis allowed the identification of a gene cluster involved in both the fungal antagonism and the production of a soluble tropolonoid compound. The ethyl acetate extract from culture supernatant showed a dose‐dependent inhibitory effect against the phytopathogenic fungus Macrophomina phaseolina. The main compound present in the organic extract was identified by spectroscopic and X‐ray analyses as 7‐hydroxytropolone (7HT). Its structure and tautomerism was confirmed by preparing the two key derivatives 2,3‐dimethoxy‐ and 2,7‐dimethoxy‐tropone. 7HT, but not 2,3‐ or 2,7‐dimethoxy‐tropone, mimicked the fungal inhibitory activity of the ethyl acetate extract from culture supernatant. The activity of 7HT, as well as its production, was barely affected by the presence of up to 50 μM added iron (Fe+2). To summarize, P. donghuensis SVBP6 produces 7HT under the positive control of the Gac‐Rsm cascade and is the main active metabolite responsible for the broad‐spectrum inhibition of different phytopathogenic fungi. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
14622912
Volume :
22
Issue :
7
Database :
Complementary Index
Journal :
Environmental Microbiology
Publication Type :
Academic Journal
Accession number :
144543907
Full Text :
https://doi.org/10.1111/1462-2920.14925