RESUMEN
PURPOSE: This study aimed to identify the antagonistic bacteria from the rhizosphere of healthy bananas that can effectively suppress the Fusarium wilt of banana, and to further investigate the inhibitory mechanism. METHOD: The primary and secondary screening techniques were implemented using the double-plate and fermentation antagonism methods. The strain was identified based on physiological and biochemical tests, 16S rRNA gene sequencing, and specific gene amplification. The effects of crude extract on the protein content, lipid peroxidation, and pectinase activity of mycelia were determined from the identified isolates. RESULTS: Two antagonistic bacteria, JF-4 and JF-5, were screened and initially identified as Bacillus subtilis (GenBank: OR125631) and B. amylum (GenBank: OR125632). The greenhouse experiment showed that the biological control efficiency of the two antagonists against the Fusarium wilt of banana was 48.3% and 40.3%, respectively. The catalase content produced by lipid peroxidation increased significantly after treatment with the crude extracts of JF-4 and JF-5 at concentrations of 0.69 µmol/L and 0.59 µmol/L, respectively. The protein and ergosterol content and pectinase activity decreased significantly. The two antagonistic bacteria might inhibit the growth of pathogens by enhancing lipid peroxidation and decreasing the synthesis of cell metabolites. Twenty compounds were identified by gas chromatography-mass spectrometry (GC-MS). B. subtilis JF-4 was further sequenced and assembled to obtain a complete circular chromosome genome of 681,804,824 bp. The genome consisted of a 4,310,825-bp-long scaffold. CONCLUSION: The findings of this study may help elucidate the mechanism behind this biocontrol isolate.
RESUMEN
A novel nanocomposite consisting of α-Fe2O3, Mn3O4 and reduced graphene oxide (r-GO) has been facilely synthesized through a two-step method: solvothermal reaction for Mn3O4-modified α-Fe2O3 (α-Fe2O3/Mn3O4) and self-assembly process for combining α-Fe2O3/Mn3O4 with r-GO (α-Fe2O3/Mn3O4/r-GO). The morphology and structure of the nanocomposite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that rod-like hematite was modified by Mn3O4 and dispersed on the surface of r-GO. Raman and Fourier transform infrared spectra (FTIR) showed superior interfacial contacts between α-Fe2O3/Mn3O4 and r-GO. Ultraviolet-visible diffuse reflectance spectroscopy (DRS) and photoelectrochemical characterization revealed a high light-harvesting efficiency, a lowered overpotential for water oxidation and an excellent charge transfer performance of α-Fe2O3/Mn3O4/r-GO nanocomposite with heterostructures. The photocatalytic oxygen evolution from the optimized photocatalyst was up to 1406.2 µmol g(-1) in 10 h of UV-vis light irradiation and the quantum yield was ca. 4.35% at 365 nm. Our investigation suggests that constructing a catalyst with heterostructures is a promising method to enhance photocatalytic activity.
RESUMEN
A novel composite composed of TiSi(2), graphene and RuO(2) nanoparticles was fabricated by a one-pot deposition method using reduced graphene oxide (RGO) as a supporting matrix and RuCl(3) as the RuO(2) precursor. The resulting RuO(2)/TiSi(2)/RGO composite was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectra, photoelectrical response and electrochemical impedance spectra. The results indicated that the three components in the composite were effectively contacted, thus facilitating the photogenerated charges transfer and separation through multiple routes. By using the composite as a photocatalyst for visible-light water splitting the average hydrogen production rate could reach 97.5 µmol h(-1) g(-1), which is higher than that from RuO(2)/TiSi(2) and pure TiSi(2) systems under the same conditions.