Nocardioides sp. strain WSN05-2, isolated from a wheat field, degrades deoxynivalenol, producing the novel intermediate 3-epi-deoxynivalenol

Abstract

The mycotoxin deoxynivalenol (DON) causes serious problems worldwide in the production of crops such as wheat and barley because of its toxicity toward humans and livestock. A bacterial culture capable of degrading DON was obtained from soil samples collected in wheat fields using an enrichment culture procedure. The isolated bacterium, designated strain WSN05-2, completely removed 1,000 μg/mL of DON from the culture medium after incubation for 10 days. On the basis of phylogenetic studies, WSN05-2 was classified as a bacterium belonging to the genus Nocardioides. WSN05-2 showed significant growth in culture medium with DON as the sole carbon source. High-performance liquid chromatography analysis indicated the presence of a major initial metabolite of DON in the culture supernatant. The metabolite was identified as 3-epi-deoxynivalenol (3-epi-DON) by mass spectrometry and (1)H and (13)C nuclear magnetic resonance analysis. The amount of DON on wheat grain was reduced by about 90% at 7 days after inoculation with WSN05-2. This is the first report of a Nocardioides sp. strain able to degrade DON and of the yet unknown 3-epi-DON as an intermediate in the degradation of DON by a microorganism.

Fig. 1

Structure of deoxynivalenol (3α,7α,15-trihydroxy-12,13-epoxytrichothec-9-en-8-one)

Fig. 2

Phylogenetic tree based on 16S rRNA gene sequences of the strain WSN05-2 (AB282680) and related microorganisms. The bar indicates 1% sequence divergence

Fig. 3

Degradation of DON by the strain WSN05-2 in MM containing DON at 1,000 μg/mL (filled circle, open circle), 100 μg/mL (filled triangle, open triangle), or 10 μg/mL (filled square, open square) and growth of the strain in these media. Filled symbols DON concentration, Open symbols growth of WSN05-2

Fig. 4

HPLC elution profile of extracted DON-degrading culture medium. The strain WSN05-2 was grown for 50 h in MM containing 1,000 μg/mL DON

Fig. 5

COSY and selective NOESY correlations of DON (a) and compound A, a DON metabolite (3-epi-DON) (b)

Fig. 6

Degradation of DON by WSN05-2 in MM containing 1,000 μg/mL of DON. Filled circle peak area of DON, Triangle peak area of compound A, Square peak area of compound B, Open circle growth of WSN05-2

Fig. 7

Decrease of DON on DON-inoculated wheat grains by strain WSN05-2. The amount of DON was analyzed by HPLC after 0, 3, and 7 days. Different letters indicate significant differences (p = 0.05), as determined by a Tukey test