In order to select a cyanide-resistant and anti peach crown gall biocontrol bacterium.Antagonistic Actinomycetes were isolated by the different concentrations of KCN in culture medium and screened by punching assay.Cyanide-resistant and antagonistic Actinomycetes strain G-19 was screened for the bioactivity using Agrobacterium tumefaciens (At) as a target strain through the plating confrontation culture method.The fermentation broth of G-19 had a high inhibitory effect on At with an inhibition ring at 21.66 mm in diameter.The bacteriostatic action mainly shown in follow aspects:the crude extract reduced the growth logarithmic phase of At,and maintained the mycelium density in a low level.Moreover,the cell wall was curving,wizening,followed by the structure rupture,cytoplasm condensate to the margin,the center etherealized,even formed a cavity;the membrane permeability increased and cause cellular inner substance of At to release;no damage however on DNA of pathogenic bacteria was seen.Therefore,it can be adjudged that the inhibitory effect mechanism of G-19 against At was to destroy the structure of cell wall and to increase the permeability of cell membrane.%为了筛选耐氰并抗桃根癌病的微生物菌株,以不同浓度的KCN培养基作为选择培养基,以根癌农杆菌为靶标菌,通过平板对峙培养的方法,筛选出了耐氰放线菌G-19,其发酵液代谢产物对根癌农杆菌有明显的抑制作用,抑菌圈直径为21.66 mm.其抑菌作用主要表现在3个方面:使得病原菌的生长对数期缩短,菌体浓度处于低水平状态；使病原菌的细胞壁弯曲、皱缩,继之结构发生破裂,细胞质向边缘凝聚,中心变得稀薄,甚至形成空腔；使细胞膜的通透性增加,导致病原菌的细胞质液外泄；但未见到病原菌DNA的损伤.因此,认为G-19菌株抑菌的作用机理是使根癌病原菌的细胞壁结构破坏和膜透性增加.
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