Purification and heterologous expression of a novel antifungal protein from Bacillus subtilis strain Z-14

Abstract

Background: Wheat sheath blight, a soil borne fungal disease caused by Rhizoctonia cerealis, is considered as one of the most serious threats to wheat worldwide. Bacillus subtilis Z-14 was isolated from soil sampled from a wheat rhizosphere and has been confirmed to have strong antifungal activity against R. cerealis. Results: An antifungal protein, termed F2, was isolated from the culture supernatant of Z-14 strain using precipitation with ammonium sulfate, anion exchange chromatography, and reverse phase chromatography. Purified F2 had a molecular mass of approximately 9 kDa, as assessed using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Edman degradation was used to determine the amino acid sequence of the N-terminus, which was NH2-ASGGTVGIYGANMRS. This sequence is identical to a hypothetical protein RBAM_004680 (YP_001420098.1) synthesized by B. amyloliquefaciens FZB42. The recombinant F2 protein (rF2) was heterologously expressed in the yeast host Pichia pastoris, purified using Ni‑affinity column, and demonstrated significant antifungal activity against R. cerealis. The purified rF2 was thermostable, retaining 91.5% of its activity when incubated for 30 min at 100 °C. rF2 maintained its activity under treatment by proteinase K and trypsin.Conclusions: A novel antifungal protein F2 was purified from biocontrol Bacillus subtilis Z-14 strain fermentation supernatant and heterologously expressed in Pichia pastoris to certificate the antifungal activity against R. cerealis and the validity of gene sequence of protein F2. Considering its significant antifungal activity and stable characteristics, protein F2 presents an alternative compound to deal with fungal infections caused by R. cerealis.

Graphene-enabled active terahertz focusing with wide tuning range

“…Since the chemical potential of graphene can be changed by applying various bias gate voltages [27], the modulation of the metasurface to the wavefront can be dynamically adjusted. So far, some tunable metalenses composed of metallic antennas and monolayer graphene have been proposed [28][29][30][31]. However, the focal tuning of these devices can only achieve a few wavelengths, because the phase change introduced by graphene is relatively small.…”