Screening of microorganisms against Oncomelania hupensis and assessing the molluscicidal efficacy

Abstract:

[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 16s rRNA 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 (χ2=21.286, P=0.002); And then the fermented liquor group had also significant differences (χ2=17.298, P=0.008); The bacteria suspension group had not significant differences (χ2=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 GenBank: 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.

Key words:oncomelania hupensis, microorganism, screening, molluscicidal efficacy, Molecular phylogeny