山核桃干腐病拮抗细菌的鉴定及其抑菌效果

在山核桃干腐病病原菌的培养过程中,发现1株具有抑菌活性的生防细菌BS111,通过划线培养、形态学及分子生物学的方法进行了山核桃干腐病病原菌拮抗菌的分离纯化及鉴定,并采用平板对峙培养法研究了拮抗菌对山核桃干腐病病原菌的抑菌活性,分别测定了拮抗菌的生长曲线以及无菌滤液不同培养时间不同浓度的抑菌活性,同时对拮抗菌无菌滤液的抑菌活性稳定性进行了研究,并通过光学显微镜研究了其抑菌机理。鉴定结果表明,BS111为枯草芽孢杆菌(Bacillus subtilis)。对峙培养结果显示,该拮抗菌菌体对山核桃干腐病病原菌具有明显的抑制作用,抑菌圈直径为18 mm。对拮抗菌生长曲线以及抑菌活性随时间的变化的测定结果显示,拮抗菌BS111在12~24 h为对数期,24 h后进入稳定期,36 h后进入衰亡期,无菌滤液在前12 h抑菌率几乎为0,在24 h时抑菌率迅速增长至70.65%,在60~72 h,抑菌效果有明显提高,最高抑菌率为83.26%。对不同浓度无菌滤液抑菌活性的测定结果表明,抑菌活性随体积分数的降低而下降,EC50值为4.16%。抑菌活性稳定性研究结果表明,无菌滤液对温度不敏感,随p H的升高抑菌活性上升,经紫外光照射后抑菌活性有部分提高。通过光学显微镜观察,无菌滤液能使菌丝变粗,弯曲,有褶皱,部分原生质体消失,菌丝顶端膨大变粗等。

Identification and Antibacterial Effect of Antagonistic Bacteria of Carya cathayensis

In order to explore one kind of bio-control agent against canker disease of Carya cathayensis which was caused by Bot-ryosphaeria dothidea, the antagonistic bacteria strain BS111 was found, isolated and identified by the method of streak cul-tivation, morphology and molecular biology.The antibacterial activity of antagonistic bacterium against B.dothidea was studied by confronting incubation.The grow curve of antagonistic bacteria strain and the antibacterial activity of different in-cubation time and different concentration were measured.The antibacterial activity stability was studied.Primary antibacte-rial mechanism was studied by optical microscope.BS111 was identified as Bacillus subtil s.Confronting incubation showed that antagonistic bacteria BS111 thallus had significant inhibition effect against B.dothidea.The diameter of the inhibition zone was 18 mm.BS111 was in the logarithmic phase between 12 and 24 h.It went into the stable phase after 24 h, and in-to the decline phase after 36 h.The antibacterial rate of sterile culture filtrate was nearly 0 during the first 12 h.The anti-bacterial rate was increased to 70.65％rapidly during 24 h, and the antibacterial effect was improved significantly from 60 to 72 h with the highest antibacterial rate of 83.26％.With the decrease of the content, the bacteriostatic activity decreased and EC50 was 4.16％.The results of the stability of antibacterial activity showed that the sterile culture filtrate was not sen-sitive to temperature and the antibacterial activity increased with the increase of pH.After UV irradiation, antibacterial ac-tivity was improved partly.Analysis of the probable antifungal mechanism indicated that sterile culture filtrate could make hypha coarsen, bent and fold, it could also make part of the protoplast disappear, and the top of the hypha was enlarged and thickened.