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【目的】筛选出一种高效、持久、安全及价廉的灭螺微生物,对其进行鉴定并观察其抑螺功效。【方法】从钉螺孳生的土壤中筛选出4株灭螺活性较强的菌株(B8、B27、B36、B59),显微镜观察菌株形态和革兰氏染色均为G+杆菌。不同分离胶浓度的SDS-PAGE分析其灭螺活性成分;优势菌株经16S r RNA扩增后,PCR产物测序,序列比对,构建系统发育树鉴定其种属。【结果】灭螺结果表明,各试验组中发酵上清液各菌株间灭螺效果差异有统计学意义(χ2=21.286,P=0.002);细菌发酵液各菌株间差异也有统计学意义(χ2=17.298,P=0.008);菌体悬液各菌株间差异无统计学意义(χ2=7.579,P=0.271);此外,B59菌株的灭螺效果优于其它菌株,尤其是其发酵上清液浸泡48 h和72 h钉螺死亡率高达73.3%和96.7%。SDS-PAGE发现在B59细菌上清液中无蛋白带出现,推测其灭螺活性物质可能是其他成分;分子系统发育分析结果显示B59菌株位于Bacillus cereus(CP001746)分支上,一致性达100%。【结论】B59菌株的发酵上清液灭螺效果最好,其灭螺活性物质可能不是蛋白质,B59菌株被鉴定为Bacillus cereus。
【Objective】 The objective of this study was to screen out a highly efficient, long-lasting, safe and cheap molluscicidal microorganism and to identify and monitor its efficacy. 【Method】 Four strains (B8, B27, B36, B59) were screened from soils breeding snails. The morphology and Gram stain of the strains were all G + bacilli. SDS-PAGE analysis of the different separation gel concentration of the genus molluscic; the dominant strains were amplified by 16S rRNA, PCR products were sequenced, sequence alignment, phylogenetic tree construction of its species. 【Result】 The result of snail killing showed that there were significant differences in the snail killing effect among the strains in each group (χ2 = 21.286, P = 0.002). There was also significant difference between the strains in the bacterial fermentation broth (χ2 = = 17.298, P = 0.008). There was no significant difference between the bacterial strains (χ2 = 7.579, P = 0.271). In addition, the effect of snail elimination of B59 was better than other strains, especially the fermentation supernatant The death rates of snails at 73 h and 48 h after soaking were 73.3% and 96.7%, respectively. SDS-PAGE showed no protein bands appeared in the supernatant of B59 bacteria, suggesting that the molluscicidal activity might be other components. Molecular phylogenetic analysis showed that the B59 strain was located on the branch of Bacillus cereus (CP001746) with 100% identity. 【Conclusion】 The results showed that the genomic DNA of B59 strain was the best, and its molluscicidal activity was probably not a protein. The strain B59 was identified as Bacillus cereus.