嗜线虫致病杆菌的抑菌物质及抑菌活性

Identification and Activity of Antibacterial Substance from Xenorhabdus nematophila var.Pekingense

嗜线虫致病杆菌北京变种（Xenorhabdus nematophila var．pekingense）是从北京地区采集的小卷蛾斯氏线虫（Steinernema carpocapsae）肠道内分离的共生细菌，具有自主知识产权，分离纯化出其发酵代谢物中的抗菌物质，进行抗菌活性测定，对研究该菌的抑菌机理以及开发利用具有重要意义。本文从该菌株代谢物中分离获得的抗菌物质经紫外光谱、红外光谱、核磁共振、高分辨质谱以及理化性质分析，鉴定为Xenocoumacin 1。用平板含毒培养基法测定了该物质对12种植物病原真菌的抑菌活性。研究表明，分离的活性物质具有较强的抑制活性，浓度在10μg／mL时，对黄瓜疫霉病菌、苎麻疫霉病菌、辣椒疫霉病菌，西葫芦灰霉病菌，苹果斑点落叶病菌的菌丝抑制率为100％。对草莓疫病病菌、苹果腐烂病菌、苹果褐斑病菌、着茄灰霉病菌、苹果轮纹病菌抑制率分别为86.8％、79．4％、79．5％、62．6％、53．6％；对其中6种真菌的EC50为0．25-4．17 μg／mL，该物质对疫霉属真菌抑制作用最强，并能引起番茄晚疫病菌的菌丝生长畸形，原生质外溢。本文对开发新型生物杀菌剂的研究奠定了基础。

Xenorhabdus nematophilus vat. pekingensis CB6 strain is symbiotic bacteria with Steinernema carpocapsaea and is carried in the intestine of the infective juvenile （IJ） stage of the emtomopathogenic nematode. It is significant to identify and bioassay antibacterial substance from metabolites of Xenorhabdus nematophila vat. pekingense. The antibacterial substance was identified as Xenocoumacin 1 by ^1H NMR, ^13C NMR, mass spectrum, infrared and ultraviolet absorption spectrum. The substance inhibited broad-spectrum plant pathogenic fungi. The mycelial growth of Phytophthora boehmeriae, P. melonis, P. infestance P. capsici, P. cactorum Botrytis cirterea and Alterinaria alternata was completely inhibited at 10 μg/mL concentration. Tile EC50 of 6 fungi species was 0.25 - 4.17 μg/mL.The inhibitory activity to Phytophthora spp.was the highest among tested 12 fungi species. The antibacterial substance could result in abnormal branching increasement, liyphae tip inflation and cytoplasm leak of P. infestance. The research will establish a base for development of novel biofungieide.