Studies on antimicrobial activity of metabolites of symbiotic bacteria associated with entomopathogenic nematodes

Chinese. 嗜线虫致病杆菌Xenorhabdus nematophila YL001(简称YL001)和伯氏致病杆菌Xenorhabdus bovienii YL002(简称YL002)是分别从陕西杨凌土壤中筛选的2株昆虫病原线虫体内分离鉴定获得的共生菌。对这2株昆虫病原线虫共生菌发酵液及其无菌滤液的抑菌作用进行了研究。室内活性测定结果表明，2菌株对供试的14种植物病原真菌和5种病原细菌均有不同程度的抑制作用。其中，YL001发酵液对烟草赤星菌、番茄早疫菌、辣椒疫霉菌、南瓜枯萎菌、黄瓜炭疽菌和稻瘟菌，YL002发酵液对辣椒疫霉菌、黄瓜炭疽菌、稻瘟菌和小麦纹枯菌的抑制率均在75%～100%；无菌滤液仅对辣椒疫霉菌有较强的抑制作用，EC50分别为16.65和15.19 mL/L；YL001和YL002发酵液及其无菌滤液均对水稻白叶枯菌和金黄色葡萄球菌有较强的抑制作用，对大肠杆菌和沙门氏菌的抑制作用较弱。盆栽试验结果表明，辣椒种子用YL001和YL002发酵液处理后，对辣椒疫霉病的防治效果分别为60.6%和73.2%；100 mL/L发酵液处理土壤后，对辣椒疫霉病的防治效果分别为48.72%和74.34%。

English. Studies on antimicrobial activity of metabolites of X. nematophilus YL001 and X. bovienii YL002 show that both symbiotic bacteria had different antimicrobial activities against 14 species of plant pathogenic fungi and 5 species of bacteria. The plant pathogenic fungi were almostly inhibited by the fermented liquid, and the inhition rate was 75%-100%. Phytophthora capsici was only completely inhibited by cell-free aqueous filtrates of fermented liquid. After diluted 10 fold, the cell-free aqueous filtrates of fermented liquid had highly antimicrobial activity against Phytophthora capsici, and the EC50 was 16.65 and 15.19 mL/L respectively. When capsicum seeds were soaked into the cell-free aqueous filtrates of fermented liquid for 6 h prior to planting, the disease reduction reached 60.6% and 73.2% 12 days after planting. When disease soil treated with 100 mL/L the cell-free aqueous filtrates of fermented liquid and metalaxl, the disease reduction reached 48.72% and 74.34%. YL001 and YL002 had higher antibacterial activity against Xanthomonas campestris and Staphylococcus aureus, but lower antibacterial activity against E. coli. and Salmonella typhi.