可可链霉菌182-2活性代谢产物对烟草赤星病菌的作用

摘要

[目的]明确可可链霉菌（Streptomyces cacaoi）182-2的活性代谢产物--KA08对烟草赤星病菌（Alternariaalternata）的抑菌活性及其机理，为后续农用抗生素产品开发和应用提供科学依据。[方法]采用菌丝湿重法和培养皿中萌发法，测定KA08对烟草赤星病菌菌丝生长和孢子萌发的抑制作用；采用电导率法和紫外吸收法测定其对细胞膜渗透性、麦角甾醇含量、脂质过氧化程度、可溶性蛋白含量的影响。[结果]KA08对烟草赤星病菌菌丝生长和孢子萌发均有强烈的抑制作用，同时，还可造成菌丝节间缩短、扭曲，芽管顶端膨大，并产生大量囊状膨大物。处理24 h时，对孢子萌发的抑菌中浓度为177.53µg·mL-1。抑菌机理研究发现KA08能导致菌丝体内电解质泄漏，细胞膜上麦角甾醇含量显著降低，脂质过氧化产物-丙二醛含量明显升高，并显著抑制菌丝体内蛋白质含量。[结论]农抗KA08对烟草赤星病菌具有显著抑制作用，主要通过抑制菌丝细胞膜上麦角甾醇合成，引发细胞膜脂质过氧化而使病菌细胞膜受损、通透性增加，从而导致菌丝生长受阻。细胞膜是KA08的主要作用位点之一。%[Objective] The objective of this study is to understand the antifungal activity and mechanism of KA08 produced by Streptomyces cacaoi strain 182-2 against Alternaria alternata so as to provide a scientific basis for further product development and application.[Method]Estimation of mycelia wet weight and spore germination in petri dish method were used to test the inhibitory effect of KA08 on mycelia growth and spore germination. Electrical conductivity method was used to test the permeability of pathogen plasma membrane, and the ultraviolet absorption method was employed to detect the content of ergosterol, MDA and soluble protein.[Result]KA08 had a remarkable inhibition effect on mycelia growth and spore germination. It caused shorter and twisted nodes, abnormal tubes with tips expanded or deformed, or saclike expansions. Twenty-four hours after treatment, the EC 50 of KA08 against conidial germination of A. alternata was 177.53 µg·mL-1. Studies on the action mechanism of KA08 found out that the electrical conductivity of the cultural filtrate increased obviously after the pathogen was treated with KA08, indicating the leakage of protoplasm from the mycelia. The ergosterol content in the cell membrane of mycelia decreased, remarkably. The content of MDA in the mycelia and the cultural filtrate increased notably, and the protein content in the mycelia reduced greatly.[Conclusion]KA08, the active metabolite of strain 182-2, has obvious inhibitory activities against A. alternata. Its bioactivity lies in its doing damage to the pathogen cell membrane and increasing the permeability of plasma membrane through inhibiting the synthesis of ergosterol in the cell membrane and causing lipid peroxidation of the cell membrane, which resulted in the poor and abnormal mycelia growth. These results suggest that cell membrane is one of the main action sites of KA08.