Pseudomonas orientalis F9 pyoverdine, safracin and phenazine mutants remain effective antagonists against Erwinia amylovora in apple flowers.

Pseudomonas orientalis F9 pyoverdine, safracin and phenazine mutants remain effective antagonists against Erwinia amylovora in apple flowers. Appl Environ Microbiol. 2020 Feb 07;: Authors: Santos Kron A, Zengerer V, Bieri M, Dreyfuss V, Sostizzo T, Schmid M, Lutz M, Remus-Emsermann MNP, Pelludat C Abstract The recently characterized strain Pseudomonas orientalis F9, an isolate from apple flowers in a Swiss orchard, exhibits antagonistic traits against phytopathogens. At high colonisation densities, it exhibits phytotoxicity against apple flowers. P orientalis F9 harbours biosynthesis genes for the siderophore pyoverdine as well as for the antibiotics safracin and phenazine. To elucidate the role of the three compounds in biocontrol we screened a large random knockout library of P. orientalis F9 for lack of pyoverdine production or in vitro antagonism. Transposon mutants that lacked the ability for fluorescence carried transposons in pyoverdine production genes. Mutants unable to antagonise E. amylovora in an in vitro double layer assay, carried transposon insertions in the safracin gene cluster. As no phenazine transposon mutant could be identified using the chosen selection criteria we constructed a site directed deletion mutant. Pyoverdine-, safracin-, and phenazine mutants were tested for their ability to counteract the fire blight pathogen Erwinia amylovora ex vivo on apple flowers or the soil-borne pathogen Pythium ultimum in vi...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research