Purification and characterization of a novel antifungal protein from Bacillus subtilis strain B29

An antifungal protein was isolated from a culture of Bacillus subtilis strain B29. The isolation procedure comprised ion exchange chromatography on diethylaminoethyl （DEAE）-52 cellulose and gel filtration chromatography on Bio-Gel P-100. The protein was absorbed on DEAE-cellulose and Bio-Gel P-100. The purified antifungal fraction was designated as B29I, with a molecular mass of 42.3 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis （SDS-PAGE）, pl value 5.69 by isoelectric focusing （IEF）-PAGE, and 97.81% purity by high performance liquid chromatography （HPLC）. B291 exhibited inhibitory activity on mycelial growth in Fusarium oxysporum, Rhizoctonia solani, Fusarium moniliforme, and Sclerotinia sclerotiorum. The 50% inhibitory concentrations （IC50） of its antifungal activity toward Fusarium oxysporum and Rhizoctonia solani were 45 and 112 μmol/L, respectively. B29I also demonstrated an inhibitory effect on conidial spore germination of Fusariurn oxysporum and suppression of germ-tube elongation, and induced distortion, tumescence, and rupture of a portion of the germinated spores.

Insight into the antifungal mechanism of Neosartorya fischeri antifungal protein

Small, cysteine-rich, highly stable antifungal proteins secreted by filamentous Ascomycetes have great po- tential for the development of novel antifungal strate- gies. However, their practical application is still limited due to their not fully clarified mode of action. The aim of this work was to provide a deep insight into the anti-fungal mechanism of Neosartorya fischeri antifungal protein （NFAP）, a novel representative of this protein group. Within a short exposure time to NFAP, reduced cellular metabolism, apoptosis induction, changes in the actin distribution and chitin deposition at the hyphal tip were observed in NFAP-sensitive Aspergillus nidulans. NFAP did show neither a direct membrane disrupting- effect nor uptake by endocytosis. Investigation of A. nidulans signalling mutants revealed that NFAP acti- vates the cAMP/protein kinase A pathway via G-protein signalling which leads to apoptosis and inhibition of polar growth. In contrast, NFAP does not have any in- fluence on the cell wall integrity pathway, but an un- known cell wall integrity pathway-independent mitogen activated protein kinase A-activated target is assumed to be involved in the cell death induction. Taken to- gether, it was concluded that NFAP shows similarities, but also differences in its mode of antifungal action compared to two most investigated NFAP-related pro-teins from Aspergillus giganteus and Penicillium chrysogenum.

The Biocontrol Effects of the Bacillus licheniformis W10 Strain and Its Antifungal Protein Against Brown Rot in Peach

The biocontrol effects of Bacillus licheniformis W10 bacterial suspension and its antifungal protein on peach brown rot caused by Monilinia fructicola in storage peach fruits and the effects on fruit quality were investigated. The results showed that the fruit disease suppression of B. licheniformis W10 bacterial suspension and antifungal protein were significantly higher than that of the control. Inoculation of bacterial suspension and antifungal protein prior to M. fructicola gave a better biocontrol effect, and the higher concentrations of bacterial(1 × 1010 cfu · m L-1) and antifungal protein(3.0 mg · m L-1) performed better control effects. The environmental conditions, such as temperature and humidity, affected biocontrol effects of W10 bacterial suspension and antifungal protein. The influence of environment conditions on the activity of antifungal protein was less than that on bacterial suspension. Moreover, lower temperature(4 ℃) and relative humidity(RH 70%–75%) were favorable to prevent peach brown rot by W10 bacterial suspension and its antifungal protein. The W10 bacterial suspension and antifungal protein amended with calcium [0.1% Ca(NO3)2] could enhance the biocontrol effects, and obviously put off the occurrence of peach brown rot. In addition, the bacterial suspension and antifungal protein significantly reduced the natural decay rates of peach fruits during storage, and the effects were equal to carbendazim. Moreover, both W10 bacterial suspension and antifungal protein treatments did not have effects on external and internal fruit appearance, such as chromatic aberration parameter L* of flesh, flesh firmness, soluble solids content and weight loss. Therefore, the B. licheniformis W10 is a potential biocontrol factor for peach brown rot.