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Study on the Anti-Fungal Mechanism of Bacillus Amyloliquefaciens WH1

Author: ZhuFaYin
Tutor: ZhaoXiuYun；QiGaoFu
School: Huazhong Agricultural University
Course: Microbiology
Keywords: Bacillus amyloliquefaciens Lipopeptide Fungi Apoptosis
CLC: S476
Type: Master's thesis
Year: 2010
Downloads: 87
Quote: 2
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Abstract


The research shows that a variety of Bacillus can produce the the cyclic lipopeptide substance to inhibit the growth of plant pathogenic fungi. One with a wider antibacterial spectrum of this study was isolated from the roots of rice, which can produce a lipopeptide amyloliquefaciens Bacillus WH1, and through a two-step extraction, gel filtration chromatography, etc. to the purified fermentation broth from the WH1 which generates lipopeptide. After thin-layer chromatography, IR spectra, electrospray ionization mass spectrometry analysis found a the surfactin class of lipopeptide, named WH1fungin. This study also on WH1fungin antibacterial mechanism. Found in antibacterial test fungi make fungal necrosis with 100μg/ml of WH1fungin processing also detected nuclear condensation, DNA fragmentation, accumulation of reactive oxygen species (ROS), phosphatidyl serine (PS) of valgus, caspase activity increased characteristics of apoptosis. The study shows that the ROS in fungal apoptosis play a very important role in the experiment with proline, ascorbic acid or glutathione, and other reactive oxygen scavenger to the decrease in the accumulation of reactive oxygen species is detected after treatment, but the eversion of phosphatidylserine not showed a corresponding decrease, indicating WH1fungin induced apoptosis is not entirely dependent upon the accumulation of reactive oxygen species. The experiment found that fungal glucan synthase activity decreased significantly after WH1fungin processing. Reduced glucan synthase activity will cause a decrease in the amount of callose synthesis, the newly formed cells not sufficient callose synthesized cell walls, the cell walls intact cells more prone to apoptosis. Experiments using affinity chromatography to peptide fingerprint analysis with WH1fungin interacting proteins, mitochondrial F-ATPase also verified in the subsequent detection a the treatment after WH1fungin ATPase of the fungal cell activity decreased. After treating cells with FITC WH1fungin able to detect its binding to the mitochondrial membrane, and verified WH1fungin capable of acting on the mitochondria. The oligomycin mitochondrial FoF1-ATPase inhibitor added oligomycin, WH1fungin treatment of fungal cell the apoptosis phenomenon is more significant, further verify WH1fungin through role to play a role in apoptosis promote fungal mitochondrial ATPase. In summary WH1 lipopeptide generated at low concentrations can exhibit antifungal activity, by way of induction of apoptosis, apoptosis may be by inhibition of glucan synthase activity and effect in the mitochondrial ATPase completed. Lipopeptide produced by Bacillus in natural ecosystems is not sufficient to lead to perforation of the cell membrane, but can induce apoptosis, to infer induced apoptosis WH1fungin amyloliquefaciens Bacillus fungal antagonism from important role.

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CLC: > Agricultural Sciences > Plant Protection > A variety of control methods > Biological control
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