Culture Condition-Dependent Acylation Patterns of Trichothecenes in a T-2 Toxin-Producing Strain of Fusarium sporotrichioides NBRC 9955

TL;DR

This study shows how the production of toxic trichothecene compounds by a fungus varies depending on the culture conditions, which can affect toxin monitoring.

Contribution

The study reveals culture condition-dependent acylation patterns of trichothecenes in a T-2 toxin-producing Fusarium strain.

Findings

Deacetylated trichothecenes accumulate in yeast extract-rich media during late growth stages.

3-O-acetylation of T-2 toxin increases in micronutrient-poor synthetic medium at late stages.

Toxin mixtures on brown rice flour include T-2 toxin, neosolaniol, HT-2 toxin, and their acetylated forms.

Abstract

Fusarium sporotrichioides strain M-1-1, originally deposited as Fusarium solani IFO 9955 in 1974 and later moved to NBRC, is known for producing T-2 toxin. In addition to NRRL 3299, which was used in the United States to study T-2 toxin biosynthesis, NBRC 9955 has been extensively used for trichothecene research in Japan. To facilitate and accurately document studies on trichothecene biosynthesis using NBRC 9955, its phylogenetic classification and trichothecene metabolite profiles were determined. As anticipated, NBRC 9955 was classified as F. sporotrichioides, which exhibited a more distant phylogenetic relationship to other strains within the same species. Time-course TLC analyses demonstrated the accumulation of various deacetylated trichothecenes in yeast extract-rich liquid media during the late growth stages. Conversely, an increase in 3-O-acetylation of T-2 toxin was observed at late stages when cultivated in micronutrient-poor synthetic liquid medium. Northern blot analysis revealed that Tri8 expression halted in cultures with the synthetic medium, which accounts for the growth stage-dependent 3-O-acetylation observed. On a brown rice flour solid medium, the fungal strain produced mixtures of T-2 toxin, neosolaniol, HT-2 toxin, and their 3-O-acetyl derivatives. These results highlight the risk of underestimating the levels of toxic trichothecene metabolites when using the standard contamination monitoring protocols.

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