Mutual interaction of the entomopathogenic and endophytic fungus Metarhizium anisopliae with zearalenone as a native component of crude Fusarium extract

Abstract

The present study revealed the consequences of the interaction of a widely used bioinsecticide and endophyte Metarhizium anisopliae with the hazardous mycotoxin zearalenone (ZEN) as a pure substance and with ZEN as a native component of a crude Fusarium extract. In the environment, microorganisms encounter a mixture of metabolites secreted by other organisms living in the same area, not single substances. The obtained results suggest that M. anisopliae, exposed to a variety of active substances produced by Fusarium graminearum, is able to eliminate ZEN. Within 14 days, M. anisopliae biotransformed 90.8% and 85.8% of ZEN as a pure substance and ZEN as a native component of the F. graminearum extract from Rice Medium (E-Fg-RM), respectively, through reduction predominantly to α-epimers of zearalenols and zearalanols, considered more estrogenic than ZEN, which can raise concerns. Compared to pure ZEN, E-Fg-RM significantly affected the production of Metarhizium secondary metabolites by increasing the destruxins amount by approximately 20-25% and reducing the swainsonine content by 96.2%. All these findings provide a possible picture of the interaction of M. anisopliae with ZEN in the wild, mainly as a result of the use of crude extract from Fusarium, which contained a mixture of different metabolites.

Keywords: Fusarium mycotoxins; Metarhizium; Biotransformation; Secondary metabolites; Zearalenone.

Fig. 1

Growth of M. anisopliae in the cultures treated with pure zearalenone (ZEN), the extract of F. graminearum on Rice Medium (E-Fg-RM) and Potato Dextrose Broth (E-Fg-PDB), and the extract of F. culmorum on Rice Medium (E-Fc-RM) at ZEN concentrations of 1, 0.5, 0.25, and 0.1 mg L⁻¹ after 24 h of incubation. Statistically significant differences within the type of treatment (ZEN, E-Fg-RM, E-Fg-PDB, E-Fc-RM) were determined between the untreated culture (biotic control) and the culture treated with pure ZEN or the obtained extract containing ZEN at concentrations of 1, 0.5, 0.25, and 0.1 mg L⁻¹ and were marked as follows—* (p < 0.05).

Fig. 2

The elimination of zearalenone (ZEN) at the initial concentration of 1 mg L⁻¹ by M. anisopliae in the cultures treated with pure ZEN (A) and crude extract of F. graminearum from Rice Medium (E-Fg-RM) (B). SSD within the time point between ZEN and E-Fg-RM samples—* (p < 0.05).

Fig. 3

The concentration of α-zearalenol (α-ZEL) (A), β-zearalenol (β-ZEL) (B), α-zearalanol (α-ZAL) (C) and β-zearalanol (β-ZAL) (D) during biotransformation of 1 mg L⁻¹ of zearalenone (ZEN) by M. anisopliae in the cultures treated with pure ZEN and crude extract of F. graminearum from Rice Medium (E-Fg-RM). Statistically significant differences (SSD) were marked as follows: SSD for a type of sample (ZEN or E-Fg-RM) referring to the previous time point—* (p < 0.05); SSD within the time point between ZEN and E-Fg-RM samples—a (p < 0.05).

Fig. 4

Metarhizium anisopliae metabolic activity (A) and cell membrane permeability (B) after 1, 2, and 7 days of incubation in the cultures treated with pure zearalenone (ZEN) and crude extract of F. graminearum from Rice Medium (E-Fg-RM). Statistically significant differences (SSD) were marked as follows: SSD for a type of sample (ZEN or E-Fg-RM) referring to the biotic control within the time point—* (p < 0.05), ** (p < 0.001); SSD within the time point between ZEN and E-Fg-RM samples—# (p < 0.05); SSD for a type of sample (ZEN or E-Fg-RM) between the time points: 1 d and 2 d–a; 1 d and 7 d–b; 2 d and 7 d–c (p < 0.05).

Fig. 5

The concentration of destruxin A (dtxA) and destruxin B (dtxB) in the M. anisopliae mycelium after 1 d (A), 2 d (B), and 7 d (C) of incubation and in the culture medium after 1 d (D), 2 d (E), and 7 d (F) of incubation in the cultures treated with pure zearalenone (ZEN) and crude extract of F. graminearum from Rice Medium (E-Fg-RM). Statistically significant differences (SSD) were marked as follows: SSD for a type of sample (ZEN or E-Fg-RM) referring to the biotic control within the time point—* (p < 0.05); SSD within the time point between ZEN and E-Fg-RM samples—a (p < 0.05).