贝莱斯芽孢杆菌K3抗尖孢镰孢菌的特征及其作用机理

Antagonistic characteristics and mechanism of Bacillus velezensis K3 against Fusarium oxysporum

摘要:

目的 尖孢镰孢菌(Fusarium oxysporum)是一种能引起植物枯萎病的真菌病原菌，严重危害植物生长，因此采用合适且绿色的生物方法进行防治十分必要。方法 利用点菌法从红树林土壤中筛选出对尖孢镰孢菌有拮抗作用的海洋芽孢杆菌，并通过生理生化特性和16S rRNA基因序列分析对该芽孢杆菌进行鉴定。提取并探究其抑菌物质对尖孢镰孢菌的体外生物防治活性及作用机制。结果 从红树林土壤中筛选出一株对尖孢镰孢菌具有强拮抗活性的芽孢杆菌K3。通过生理生化特性和16S rRNA基因序列分析鉴定该菌株为贝莱斯芽孢杆菌(Bacillus velezensis)。菌株K3分泌的抗真菌物质具有广谱抗菌特性，对细菌和真菌均有效，该物质可能为蛋白或多肽类，具有良好的热稳定性，对尖孢镰孢菌的最小抑菌浓度(minimal inhibitory concentration, MIC)为1 mg/mL，能够显著抑制孢子萌发，可导致尖孢镰孢菌胞内的电解质、核酸和蛋白外泄。在3×MIC浓度下处理尖孢镰孢菌孢子10 h后，孢子萌发抑制率为49.85%。经处理的尖孢镰孢菌菌丝细胞完整性受损，细胞膜稳态失衡，丙二醛(malondialdehyde, MDA)含量增加，膜内超氧化物歧化酶(superoxide dismutase, SOD)、过氧化物酶(peroxidase, POD)和过氧化氢酶(catalase, CAT)活性提升。结论 从海洋源红树林筛选出的贝莱斯芽孢杆菌K3产生的抗真菌物质抑菌谱广，对尖孢镰孢菌有较强抑制活性，具有潜在的商业应用价值。

关键词:抗真菌;芽孢杆菌;作用机理;抑菌活性;尖孢镰孢菌

Abstract:

Objective Fusarium oxysporum is a fungal pathogen that causes plant wilt, severely affecting plant growth. Therefore, it is necessary to use appropriate and environmentally friendly biological methods for control of this pathogen.Methods We employed the point inoculation method to isolate a marine Bacillus strain antagonistic to Fusarium oxysporum from mangrove soil. The Bacillus strain was identified based on physiological and biochemical characteristics and 16S rRNA gene sequence. The antifungal substance was extracted from the fermentation supernatant, and the inhibitory activity and mechanism of the substance against Fusarium oxysporum were evaluated in vitro.Results A Bacillus strain with strong antagonistic activity against Fusarium oxysporum was isolated from mangrove soil and identified as Bacillus velezensis. The antifungal substance secreted by strain K3 exhibited broad-spectrum antimicrobial properties, being effective against both bacteria and fungi. This substance was likely a protein or peptide and had good thermal stability. It showed the minimum inhibitory concentration (MIC) of 1 mg/mL against Fusarium oxysporum, significantly inhibiting spore germination and causing leakage of electrolytes, nucleic acids, and proteins. The treatment with 3×MIC of the antifungal substance for 10 h showed the inhibition rate of 49.85% on the germination of Fusarium oxysporum spores. Moreover, the treated Fusarium oxysporum hyphal cells showed compromised cell integrity, disrupted membrane homeostasis, increased malondialdehyde content, and enhanced activities of superoxide dismutase, peroxidase, and catalase in the membrane.Conclusion The antifungal substance produced by B. velezensis K3 isolated from mangrove soil of marine origin exhibits a broad antimicrobial spectrum and strong inhibitory activity against Fusarium oxysporum, with potential commercial application value.

Key words:antifungal;Bacillus;mechanism;antimicrobial activity;Fusarium oxysporum