Aflatoxigenic Aspergillus Modulates Aflatoxin-B1 Levels through an Antioxidative Mechanism

Area of Science:

• Mycology
• Plant Pathology
• Biochemistry

Background:

• Aflatoxins (AFs) produced by Aspergillus section Flavi have proposed roles in fungal biology, including antioxidation and insect deterrence.
• Atoxigenic strains of Flavi are known to degrade aflatoxin B1 (B1), but the purpose of this degradation remains unclear.

Purpose of the Study:

• To investigate the role of aflatoxin degradation, specifically B1 and G1 (G1), in the antioxidative capacity of Flavi.
• To determine the impact of selenium (Se), an antioxidant, on aflatoxin levels and the fitness of toxigenic versus atoxigenic Flavi strains.

Main Methods:

• Toxigenic and atoxigenic Flavi isolates were incubated with artificial B1 and G1, with or without selenium.
• Aflatoxin levels were quantified using High-Performance Liquid Chromatography (HPLC).
• Fungal fitness was assessed by spore counts after exposure to varying concentrations of Se on 3%-sucrose cornmeal agar (3gCMA).

Main Results:

• Atoxigenic Flavi reduced B1 levels, while G1 levels remained unchanged without Se.
• Selenium treatment led to reduced B1 digestion by toxigenic Flavi and increased G1 levels.
• Selenium did not affect B1 digestion in atoxigenic Flavi or G1 levels in either strain type.
• Atoxigenic strains exhibited significantly higher fitness than toxigenic strains at 0.86 µg/g Se.

Conclusions:

• Toxigenic Flavi modulate B1 levels via an antioxidative mechanism, preferring B1 over G1 for this role.
• Atoxigenic Flavi actively degrade B1.
• The enhanced fitness of atoxigenic strains under selenium stress suggests their potential utility in biocontrol strategies against toxigenic Flavi.