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.