Identification and characterization of a novel Bacillus subtilis strain with potent antifungal activity of a flagellin-like protein.

The filamentous fungus Botrytis cinerea is an important agricultural pathogen affecting a wide range of cultivated plants. Since World War II, chemical fungicides have been the go-to method for agricultural pathogen control. However, the potential adverse environmental and health effects of these chemicals have led to an increasing demand for alternative methods of pathogen control, including biological control agents. In this study, we identified a bacterial isolate with strong antagonistic activity against B. cinerea. An analysis of the 16S rRNA gene sequence for this isolate identified it as a novel strain of Bacillus subtilis. Culture media from this isolate were harvested and fractionated using ion exchange and gel filtration chromatography. The fraction exhibiting the highest level of antifungal activity was identified, and its sequence determined by electrospray tandem mass spectrometry had significant similarity to flagellin. This flagellin-like protein was exogenously expressed in Escherichia coli, and screened for antifungal activity against B. cinerea. This flagellin-like protein demonstrated clear antifungal activity of inhibiting B. cinerea growth.