Streptomyces-Aspergillus flavus interactions: impact on aflatoxin B accumulation
C Verheecke1, T Liboz, P Anson
1a Laboratoire de Génie Chimique , Université de Toulouse , Castanet-Tolosan , France.
Summary
Certain Streptomyces species show potential as biocontrol agents, significantly reducing aflatoxins in maize by inhibiting fungal gene expression. These microbes offer a complementary approach to existing biocontrol strategies.
Area of Science:
- Agricultural Microbiology
- Mycotoxicology
- Biotechnology
Background:
- Aflatoxins, produced by Aspergillus flavus, pose a significant threat to maize safety and global trade.
- Current biocontrol methods, like Afla-guard®, exist, but complementary strategies are needed.
- Previous research identified Streptomyces species with antagonistic activity against A. flavus.
Purpose of the Study:
- To investigate the efficacy of Streptomyces species as biocontrol agents against aflatoxins in maize.
- To explore the mechanisms underlying aflatoxin reduction by selected Streptomyces strains.
- To assess the impact of Streptomyces on A. flavus gene expression related to aflatoxin biosynthesis.
Main Methods:
- Screening of Streptomyces species for antagonism against A. flavus and aflatoxin reduction.
- Selection of six promising strains for further mechanistic studies.
- Quantitative real-time PCR (RT-qPCR) to monitor the expression of aflatoxin biosynthesis genes (aflD, aflM, aflP, aflR, aflS) in A. flavus upon interaction with Streptomyces.
Main Results:
- All tested Streptomyces strains reduced aflatoxin B1 concentrations significantly (0.2-24.0% residual).
- Strains S35 and S38 significantly repressed specific aflatoxin biosynthesis genes (S35 repressed aflM; S38 repressed aflR, aflM, and aflP).
- Strain S6 demonstrated substantial aflatoxin reduction (2.3% residual) and modulated gene expression (repressed aflS, aflM; enhanced aflR), with no observed adsorption mechanism.
Conclusions:
- Streptomyces species effectively prevent aflatoxin accumulation in vitro through mechanisms involving the downregulation of aflatoxin biosynthesis gene expression.
- Specific strains, like S35, S38, and S6, exhibit distinct modes of action in controlling aflatoxins.
- These findings highlight the potential of Streptomyces as a sustainable biocontrol strategy for managing aflatoxin contamination in agricultural products.
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