灭钉螺微生物的选育及抑螺效果观察（英文）

Screening of microorganisms against Oncomelania hupensis and assessing the molluscicidal efficacy

【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 research aimed to screen the efficient, durable, safe and inexpensive molluscicidal microorganisms against Oncomelania hupensis and observe the molluscicidal effects. [Methods] The four strains（named as B8, B27, B36, B59） which were highly toxic to Oncomelania hupensis were isolated by preliminary screening from snail habitats. The colonial morphology and gram stain were observed by light microscope. The molluscicidal active fraction were analysed by different resolving gel concentration of SDS-PAGE. The ribosomal 16 S r RNA of the dominant strain were amplified and the PCR products were sequenced. Sequence alignment was adopted for the identification of the dominant strain. [Results] The four strains were Gram-positive bacilli. According to the comprehensive comparison, molluscicidal effect of the four strains had significant differences in the fermented supernatant（FS） group（χ^2=21.286, P=0.002）; And then the fermented liquor group had also significant differences（χ^2=17.298, P=0.008）; The bacteria suspension group had not significant differences（χ^2=7.579, P=0.271）. In addition, B59 strain showed the higher molluscicidal activity than the other three strains. The snails mortalities in FS group was up to 73.3% and 96.7% by immersion in 48 h and 72 h respectively. SDS-PAGE analysis revealed that there did not exsit protein band in FS of B59 strain and molluscicidal active components might be other materials. Finally, molecula phylogenetic analysis based on ITS sequence showed that strain B59（accession number in Gen Bank： KP146144） was the most homologus to 100% Bacillus cereus（accession number： CP001746） with bootstrap. [Conclusion] In summary, The effective molluscicidal components against Oncomelania hupensis exsited in the fermented supernatant of strain B59, which might not be protein. B59 strain was identified as a species of Bacillus cereus.