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Volatile-Mediated Inhibitory Activity of Rhizobacteria as a Result of Multiple Factors Interaction: The Case of Lysobacter capsici AZ78.

ABSTRACT: Plant beneficial rhizobacteria may antagonize soilborne plant pathogens by producing a vast array of volatile organic compounds (VOCs). The production of these compounds depends on the medium composition used for bacterial cell growth. Accordingly, Lysobacter capsici AZ78 (AZ78) grown on a protein-rich medium was previously found to emit volatile pyrazines with toxic activity against soilborne phypathogenic fungi and oomycetes. However, the discrepancy between the quantity of pyrazines in the gaseous phase and the minimum quantity needed to achieve inhibition of plant pathogens observed, lead us to further investigate the volatile-mediated inhibitory activity of AZ78. Here, we show that, besides VOCs, AZ78 cells produce ammonia in increased amounts when a protein-rich medium is used for bacterial growth. The production of this volatile compound caused the alkalinization of the physically separated culture medium where Rhizoctonia solani was inoculated subsequently. Results achieved in this work clearly demonstrate that VOC, ammonia and the growth medium alkalinization contribute to the overall inhibitory activity of AZ78 against R. solani. Thus, our findings suggest that the volatile-mediated inhibitory activity of rhizobacteria in protein-rich substrates can be regarded as a result of multiple factors interaction, rather than exclusively VOCs production.

SUBMITTER: Vlassi A

PROVIDER: S-EPMC7695267 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Volatile-Mediated Inhibitory Activity of Rhizobacteria as a Result of Multiple Factors Interaction: The Case of <i>Lysobacter capsici</i> AZ78.

Vlassi Anthi A Nesler Andrea A Parich Alexandra A Puopolo Gerardo G Schuhmacher Rainer R

Microorganisms 20201109 11

Plant beneficial rhizobacteria may antagonize soilborne plant pathogens by producing a vast array of volatile organic compounds (VOCs). The production of these compounds depends on the medium composition used for bacterial cell growth. Accordingly, <i>Lysobacter capsici</i> AZ78 (AZ78) grown on a protein-rich medium was previously found to emit volatile pyrazines with toxic activity against soilborne phypathogenic fungi and oomycetes. However, the discrepancy between the quantity of pyrazines in ...[more]

PMID: 33182371

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Project description:Determining the mode of action of microbial biocontrol agents plays a key role in their development and registration as commercial biopesticides. The biocontrol rhizobacterium Lysobacter capsici AZ78 (AZ78) is able to inhibit a vast array of plant pathogenic oomycetes and Gram-positive bacteria due to the release of antimicrobial secondary metabolites. A combination of MALDI-qTOF-MSI and UHPLC-HRMS/M was applied to finely dissect the AZ78 metabolome and identify the main secondary metabolites involved in the inhibition of plant pathogenic microorganisms. Under nutritionally limited conditions, MALDI-qTOF-MSI revealed that AZ78 is able to release a relevant number of antimicrobial secondary metabolites belonging to the families of 2,5-diketopiperazines, cyclic lipodepsipeptides, macrolactones and macrolides. In vitro tests confirmed the presence of secondary metabolites toxic against Pythium ultimum and Rhodococcus fascians in AZ78 cell-free extracts. Subsequently, UHPLC-HRMS/MS was used to confirm the results achieved with MALDI-qTOF-MSI and investigate for further putative antimicrobial secondary metabolites known to be produced by Lysobacter spp. This technique confirmed the presence of several 2,5-diketopiperazines in AZ78 cell-free extracts and provided the first evidence of the production of the cyclic depsipeptide WAP-8294A2 in a member of L. capsici species. Moreover, UHPLC-HRMS/MS confirmed the presence of dihydromaltophilin/Heat Stable Antifungal Factor (HSAF) in AZ78 cell-free extracts. Due to the production of HSAF by AZ78, cell-free supernatants were effective in controlling Plasmopara viticola on grapevine leaf disks after exposure to high temperatures. Overall, our work determined the main secondary metabolites involved in the biocontrol activity of AZ78 against plant pathogenic oomycetes and Gram-positive bacteria. These results might be useful for the future development of this bacterial strain as the active ingredient of a microbial biopesticide that might contribute to a reduction in the chemical input in agriculture.

Dataset Information

Volatile-Mediated Inhibitory Activity of Rhizobacteria as a Result of Multiple Factors Interaction: The Case of Lysobacter capsici AZ78.

Publications

Volatile-Mediated Inhibitory Activity of Rhizobacteria as a Result of Multiple Factors Interaction: The Case of <i>Lysobacter capsici</i> AZ78.

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