具杀线虫活性植物内生细菌的筛选和活性产物

【目的】植物寄生线虫是危害植物的重要病原物,为了筛选到能在植物体内稳定定殖并且对植物寄生线虫具有较高杀线虫活性的植物内生细菌生防菌。【方法】以松材线虫为靶标,用直接触杀法进行筛选。对高活性菌株采用正交实验优化发酵条件,测定发酵液杀线虫活性的稳定性,并对菌株进行鉴定。【结果】从6种植物中分离筛选出13株对松材线虫具有较高杀线虫活性的植物内生细菌菌株,这些菌株的发酵上清液对松材线虫处理24h杀线虫率均达到了100%;其中BCM2、SZ5、CCM7和DP1这4个菌株的杀线虫活性较高,发酵上清液稀释3倍处理24h杀线虫率均达到95%以上,DP1和SZ5菌株达到了100%;并发现部分菌株发酵液能使线虫虫体发生渗漏或消解。发酵条件优化后能使发酵液杀线虫效果提高4倍。4株高活性菌株产生的杀线虫物质均对蛋白酶稳定、耐热不耐酸碱且长时间保藏活性不下降。经过鉴定DP1和CCM7是枯草芽孢杆菌(Bacillus subtilis),BCM2和SZ5是蜡样芽孢杆菌(Bacillus cereus)。【结论】经济作物体内存在一定数量的能产生杀线虫活性物质的内生细菌,其中一些细菌产生的杀线虫物质具有较强的稳定性。认为杀线虫活性的植物内生细菌具有很大的生防潜力。

Screening endophytic bacteria against plant-parasitic nematodes

Abstract:Objective] The aim of this study was to isolate efficient high-molecular-weight polycyclic aromatic hydrocarbons (HMW-PAHs) degrading bacterial strains, and to study their degradation potential.Methods] We used sublimation method to enrich and isolate the degrading bacteria from coking plant samples. Morphological properties, the sequence homology of 16S rRNA and gyrb genes were used to identify the isolated strains. GC-MS was used to analyze the degradation potential against some HMW-PAHs. Results] A HMW-PAHs degrading bacterium, HBS1, was obtained. Strain HBS1 could use several HMW-PAHs such as pyrene,benzoanthracene,benzopyrene,chyrsene,indeno1,2,3-cd]pyrene,benzog,h,i]perylene and fluoranthene as sole carbon source for growth. Strain HBS1 was identified as Gordonia sp.. Based on the high sequence similarities (more than 99%) of both 16S rRNA gene and gyrb gene to those of Gordonia amicalis. When the initial concentration of pyrene was 50 mg/L, strain HBS1 could consume 97% of the pyrene in 17 days. One fragment of the dioxygenase gene was obtained by PCR with size about 300 bp, which was closest to the counterpart from Mycobacterium sp. with 93.8% similarity. Conclusion] We isolated a strain HBS1 from seriously PAHs-polluted soils and identified it belong to Gordonia sp.. The isolate got a great degradation potential of high-molecular weight polycyclic aromatic hydrocarbons.