杀线虫活性菌的筛选、分离与初步鉴定

从河南南阳宝天曼森林土壤样品中分离纯化细菌，以对线虫Caenorhabditis elegans的杀灭作用为筛选模型，从128株细菌中共筛选到3株杀线虫活性较高的细菌，编号分别为B、C、D。当作用于线虫24h后，它们对线虫的致死率分别为20％、25％、97％。然而发现当B和C共同作用于线虫时，致死率大为提高（约为90％），说明二者在杀线虫方面有协同作用。通过培养观察菌落形态，革兰氏染色；提取各菌种基因组，扩增16SrDNA测序，系统发育分析，确定这三株菌的鉴定结果为：菌株B与Bacillus subtilis strain xfchu2的同源性较高，为96．46％，菌株C与Stenotrophomonas maltophilia strain QT24的同源性较高，为92．75％。菌株D与荧光假单胞菌属的同源性较高。

SCREENING,ISOLATION AND IDENTIFICATION OF NEMATOCIDAL BACTERIA AGAINST CAENORHABDITIS ELEGANS

Nematocidal bacteria were screened and isolated from Baotianman＇ s forest soil sample of Nanyang, Henan. Based on the model of killing effect on Caenorhabditis elegans, three bacteria were selected from 128 strains of bacteria, which had high activity of killing nematodes and were separately numbered B, C, D. When they treated with nematodes for 24 h, the mortalities of nematodes were 20% ,25% and 97%. However, the mortality of nematodes could be greatly improved when B and C interacted with nematodes together, which indicated that the two bacteria killed nematodes synergistically. The morphological characteristics of the bacteria were analyzed through Gram stain. The 16S rDNA sequences of the bacteria were obtained by PCR. The results of the molecular identifications of the three bacteria were as follows： strain B had high homologous with Bacillus subtilis strain xfchu2 （96.46%） ; strain C had high homologous with Stenotrophomonas maltophilia strain QT24 （92.75%） ; strain D had high homologous with Pseudomonas fluorscen.