Helper bacteria halt and disarm mushroom pathogens by linearizing structurally diverse cyclolipopeptides

The bacterial pathogen Pseudomonas tolaasii severely damages white button mushrooms by secretion of the pore-forming toxin tolaasin, the main virulence factor of brown blotch disease. Yet, fungus-associated helper bacteria of the genus Mycetocola (Mycetocola tolaasinivorans and Mycetocola lacteus) m...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2020-09, Vol.117 (38), p.23802-23806
Main Authors: Hermenau, Ron, Kugel, Susann, Komor, Anna J., Hertweck, Christian
Format: Article
Language:English
Subjects:
Bacteria
Bioassays
Biological Sciences
Brown blotch
Cleavage
Deactivation
Detoxification
Fractionation
Fungi
Inactivation
Ionization
Ions
Mass spectrometry
Mass spectroscopy
Mushrooms
Pathogens
Pore formation
Proteomes
Swarming
Toxins
Virulence
Virulence factors
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Summary:The bacterial pathogen Pseudomonas tolaasii severely damages white button mushrooms by secretion of the pore-forming toxin tolaasin, the main virulence factor of brown blotch disease. Yet, fungus-associated helper bacteria of the genus Mycetocola (Mycetocola tolaasinivorans and Mycetocola lacteus) may protect their host by an unknown detoxification mechanism. By a combination of metabolic profiling, imaging mass spectrometry, structure elucidation, and bioassays, we found that the helper bacteria inactivate tolaasin by linearizing the lipocyclopeptide. Furthermore, we found that Mycetocola spp. impair the dissemination of the pathogen by cleavage of the lactone ring of pseudodesmin. The role of pseudodesmin as a major swarming factor was corroborated by identification and inactivation of the corresponding biosynthetic gene cluster. Activity-guided fractionation of the Mycetocola proteome, matrix-assisted laser desorption/ionization (MALDI) analyses, and heterologous enzyme production identified the lactonase responsible for toxin cleavage. We revealed an antivirulence strategy in the context of a tripartite interaction that has high ecological and agricultural relevance.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2006109117