How Fungi and Bacteria Communicate and Break Down Toxins

Jenn Hoskins
25th May, 2024

How Fungi and Bacteria Communicate and Break Down Toxins

This fungus, Penicillium expansum, causes apple rot by producing the mycotoxin patulin, a key virulence factor that the study found can be neutralized by a bacterial lactonase enzyme.

Photo adapted from: Judy Dobles / CC BY (Source)

Key Findings

  • The study by the Migal-Galilee Research Institute explored how bacterial enzymes interact with fungal pathogens in apples
  • The enzyme EaAiiA from Erwinia bacteria can break down patulin, a toxic compound produced by the fungus Penicillium expansum
  • This degradation of patulin by EaAiiA reduces apple disease and lowers patulin production, improving fruit health and quality
The study conducted by the Migal-Galilee Research Institute[1] focuses on the interaction between bacterial enzymes and fungal pathogens in apples, specifically how bacterial lactonases can degrade harmful compounds produced by fungi. This research is particularly relevant given the significant role that microbial communities play in fruit health and postharvest quality. Erwinia spp., a type of bacteria found in the native apple microbiome, and Erwinia amylovora, a known fruit tree pathogen, were used as model organisms to explore this interaction. The researchers discovered that both types of Erwinia are inhibited by patulin, a toxic compound produced by the fungus Penicillium expansum. At concentrations that inhibited the growth of E. amylovora, the expression of a lactonase enzyme encoded by the gene EaaiiA was increased. This enzyme not only degrades quorum sensing molecules (AHLs) but also breaks down patulin, reducing its toxic effects. The ability of EaAiiA to degrade patulin was demonstrated both in vitro (in a controlled laboratory environment) and in vivo (within living apple tissues). This degradation led to reduced apple disease and lower patulin production by P. expansum. In co-cultures of fungi and bacteria, a strain of E. amylovora lacking the eaaiia gene failed to protect apples from P. expansum infections, underscoring the enzyme's crucial role in mitigating fungal pathogenicity. Previous studies provide a broader context for these findings. For instance, research has shown that apples harbor distinct bacterial communities in their various tissues, with the fruit pulp and seeds being hotspots for bacterial colonization[2]. These bacterial communities are influenced by factors such as organic versus conventional farming practices, which affect their diversity and evenness but not their overall abundance. This background information is essential to understanding how the bacterial enzyme EaAiiA might interact with fungal pathogens within the apple microbiome. Another relevant study examined the impact of postharvest treatments on the microbiome of apples, revealing that washing, waxing, and low-temperature storage significantly alter bacterial and fungal communities[3]. These changes are tissue-specific, with the peel being most affected. This study highlights the dynamic nature of the apple microbiome and the potential for postharvest practices to influence microbial interactions, including those involving patulin degradation. Furthermore, a study on the apple resistome (the collection of all antimicrobial resistance genes) found that apples harbor various antibiotic resistance genes, some of which are clinically relevant[4]. This resistome is influenced by postharvest storage and transport, which can increase the abundance of certain bacterial orders like Enterobacteriales and diversify the pool of resistance genes. This finding underscores the importance of monitoring microbial communities and their resistance profiles in food products, as they can impact food safety and disease management. The current study builds on these previous findings by demonstrating a specific mechanism through which bacterial enzymes can mitigate fungal pathogenicity in apples. By degrading patulin, the lactonase enzyme EaAiiA not only reduces fungal toxicity but also enhances the overall health and quality of the fruit. This research suggests that leveraging bacterial enzymes could be a viable strategy for controlling postharvest diseases in apples, potentially reducing reliance on chemical treatments and improving food safety. In conclusion, the study conducted by the Migal-Galilee Research Institute provides valuable insights into the complex interactions between bacterial and fungal pathogens in apples. By elucidating the role of bacterial lactonases in degrading harmful fungal compounds, this research offers a promising avenue for enhancing postharvest disease management and ensuring the safety and quality of apple produce.

GeneticsBiochemMycology

References

Main Study

1) Bacterial-fungal crosstalk is defined by a fungal lactone mycotoxin and its degradation by a bacterial lactonase.

Published 24th May, 2024

https://doi.org/10.1128/aem.00299-24

Related Studies

2) An Apple a Day: Which Bacteria Do We Eat With Organic and Conventional Apples?

https://doi.org/10.3389/fmicb.2019.01629

3) Effect of Washing, Waxing and Low-Temperature Storage on the Postharvest Microbiome of Apple.

https://doi.org/10.3390/microorganisms8060944

4) The microbiome and resistome of apple fruits alter in the post-harvest period.

https://doi.org/10.1186/s40793-022-00402-8


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