Toxicity screening and identification of bacteria isolated from snails Nassarius semiplicatus and their habitat
半褶织纹螺(Nassarius semiplicatus)及其生活环境中分离培养的细菌毒性测试与种类分析

Objective] Tetrodotoxin and its analogues (TTXs) were responsible for the poisoning incidents associated with snail Nassarius spp. We studied bacteria isolated from toxic snails as well as their habitat to probe into the relationship between bacteria and toxicity of nassariid gastropod. Methods] Two snail samples were collected from Sheyang, Jiangsu Province on June 13 and 19, 2006, and the toxicity of the snail samples was tested with mouse bioassay method. Bacteria were isolated from the snail samples and from their habitat. A part of isolated bacteria were then cultured in the lab, and TTX in bacteria were screened with an ELISA method. Results] The snails collected were identified as Nassarius semiplicatus, and the toxicity of the 2 samples were 247 mouse unit (MU) and 270 MU / 100g tissue (wet weight), respectively. TTX was detected in 9 strains among the 14 strains of bacteria isolated from the snail samples and their habitat. TTX content in the toxic strains was very low, which ranged from 15 ng/g to 96 ng/g. Partial of the 16S ribosomal DNA (rDNA) of the toxic strains were then sequenced after PCR amplification, and the toxic strains of bacteria were tentatively identified based on the alignment of these sequences with published data. Toxic strains were closely affiliated with Vibrio, Shewanella, Planococcus, Marinomonas, Photobacterium. Conclusion] These findings suggested that TTX-producing bacteria may play an important role in TTX production or accumulation in nassariid gastropod.