Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2003
Publication Date: 5/20/2003
Citation: Cuero, R., Ouellet, T., Yu, J., Mogongwa, N. 2003. Metal Ion Enhancement on Fungal Growth, Gene Expression and Aflatoxin Synthesis in Aspergillus flavus: RT-PCR Characterization. Journal of Applied Microbiology. 94:953-961. Interpretive Summary: Aflatoxins are toxic and extremely carcinogenic compounds produced by the two common fungi, Aspergillus flavus and A. parasiticus. These toxins contaminate agricultural commodities such as corn, cotton, peanuts, and tree nuts resulting in significant economic losses or food safety problems. The effects of metal ions on fungal growth and aflatoxin production in the liquid culture have been studied. This will help us to better understand the trace element factors that affect fungal growth and aflatoxin formation. This information may provide insight into the regulation of aflatoxin synthesis and help in devising strategies for reduction or elimination of aflatoxin contamination in foods and feeds.
Technical Abstract: The influence of metal ions (Zn**+2 , Cu**+2 and Fe**+2 ), as single or in mixed treatments, on enhancement of fungal growth, total RNA, mRNA of representative aflatoxin pathway gene (omt A), as well as the synthesis of aflatoxin and its precursor, O-methylsterigmatocystin, were studied in submerged cultures of toxigenic Aspergillus flavus. The direct effects of metal ions on fungal growth and aflatoxin synthesis varied according to the type of metal ion and combination of ion mixture. All mixed metal ions treatments boosted total RNA synthesis, enhanced expression of aflatoxin pathway gene (omtA), increased fungal biomass, and synthesis of aflatoxin. Triple metal ion mixtures (zinc, copper, and iron) produced the highest enhancement of the parameters, followed by the duplex mixture of zinc and copper, with the least effect induced by single zinc treatments compared with the no metal ion control. Both copper and zinc as single treatments did not affect fungal growth markedly, but they increased toxin and its precursor synthesis, and also stimulated fungal total RNA and aflatoxin pathway genes expression. The aggregate results suggest a role by metal ions both at the cellular and molecular levels. The marked effects of mixed metal ions on fungal genetic and cellular changes, reflect the actual mixed state of the metal ions in nature.