Isolation and characterization of Bacillus amyloliquefaciens MQ01, a bifunctional biocontrol bacterium with antagonistic activity against Fusarium graminearum and biodegradation capacity of zearalenone

Fusarium graminearum is the predominant pathogen related to Fusarium head blight (FHB) which causes mycotoxin contamination of grains, mainly involving zearalenone (ZEN) and deoxynivalenol. The present work aimed to isolate a bacterium capable of antagonizing various phytopathogenic fungi and degrading ZEN effectively. Through co-culture with Fusarium graminearum, the bacterial strain MQ01 was isolated from wheat rhizosphere soil for its antifungal activity and identified as Bacillus amyloliquefaciens according to its morphological, physiological and biochemical characteristics and phylogenetic trees based on sequences of the 16 S rRNA and gyrB genes. B. amyloliquefaciens MQ01 showed broad-spectrum antifungal activity against eight phytopathogens, namely F. oxysporum, Sclerotinia sclerotiorum, F. proliferatum, F. verticillioides, Colletotrichum gloeosporioides, Microdochium nivale, F. equiseti and F. semitectum. The antifungal substances were extracted, separated by native-PAGE and identified through MALDI-TOF-MS. Protein homology analysis showed that the two antagonistic components were chitin-binding protein and subtilisin, respectively. In addition, MQ01 showed a prominent degradation capacity of ZEN both in liquid medium (94.1%) and in practical samples such as corn (27.9%) and distiller's dried grains with solubles (35.3%). One of the degradation product was identified as 1(3,5-dihydroxyphenyl)-6 '-hydroxy-l'-undecen-l0 '-one by TOF-MS/MS analysis. In conclusion, B. amyloliquefaciens MQ01 shows promising prospects for use as a biocontrol agent against FHB and for ZEN degradation under field conditions.