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Evaluation of the aflatoxin biosynthetic genes for identification of the Aspergillus section Flavi
Hitomi Nakamura1, Takashi Narihiro, Naoki Tsuruoka
1International Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
Abstract:
Several fungi in the Aspergillus section Flavi have been widely used for fermentative food production, while some related species in the section are known to produce mycotoxin(s) that causes mycotic diseases. Common evolutionary markers, such as rRNA gene sequences and their internal transcribed spacers, cannot differentiate these non-aflatoxin-producing species from aflatoxin producers. Multilocus sequence analysis (MLSA) based on four aflatoxin biosynthetic genes encoding aflR, aflT, norA, and vbs, which are more variable nucleotide sequences than rRNA genes, can distinguish safe koji molds, A. oryzae and A. sojae, from aflatoxin-producing strains, A. flavus, A. toxicarius and A. parasiticus.
Insights
Differentiating safe food-grade Aspergillus fungi from toxic, mycotoxin-producing strains is crucial. Multilocus sequence analysis using aflatoxin biosynthetic genes accurately distinguishes Aspergillus oryzae and Aspergillus sojae from aflatoxin producers.
Area of Science:
- Mycology
- Food Microbiology
- Molecular Biology
Background:
- Aspergillus section Flavi includes fungi vital for food fermentation (e.g., Aspergillus oryzae, Aspergillus sojae) but also contains mycotoxin-producing species.
- Traditional markers like rRNA genes fail to distinguish safe Aspergillus strains from aflatoxin-producing ones, posing food safety risks.
Purpose of the Study:
- To develop a reliable molecular method for differentiating safe Aspergillus species used in food production from aflatoxin-producing strains.
- To identify specific genetic markers for distinguishing between non-aflatoxin-producing and aflatoxin-producing Aspergillus fungi.
Main Methods:
- Multilocus sequence analysis (MLSA) was employed.
- Four aflatoxin biosynthetic genes (aflR, aflT, norA, vbs) were targeted for sequence analysis.
- Nucleotide sequences of these genes were compared to traditional rRNA gene markers.
Main Results:
- MLSA based on aflatoxin biosynthetic genes provided clear differentiation between species.
- Safe koji molds (Aspergillus oryzae, Aspergillus sojae) were distinguished from aflatoxin-producing strains (Aspergillus flavus, Aspergillus toxicarius, Aspergillus parasiticus).
- Aflatoxin biosynthetic genes showed higher variability than rRNA genes, enhancing discriminatory power.
Conclusions:
- Multilocus sequence analysis using aflatoxin biosynthetic genes is a robust method for distinguishing safe Aspergillus food fungi from mycotoxin producers.
- This molecular approach enhances food safety by enabling accurate identification of Aspergillus strains.
- The findings support the use of specific gene sequences for fungal strain identification in food applications.
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