Premium
7‐hydroxytropolone is the main metabolite responsible for the fungal antagonism of Pseudomonas donghuensis strain SVBP6
Author(s) -
Muzio Federico M.,
Agaras Betina C.,
Masi Marco,
Tuzi Angela,
Evidente Antonio,
Valverde Claudio
Publication year - 2020
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.14925
Subject(s) - biology , antagonism , metabolite , secondary metabolite , ethyl acetate , macrophomina phaseolina , strain (injury) , pseudomonas , microbiology and biotechnology , fungus , siderophore , bacteria , gene , botany , biochemistry , genetics , anatomy , receptor
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 Tn 5 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.