水霉拮抗放线菌的分离、筛选与鉴定

Isolation,Screening and Identification of Antagonistic Actinomycetes against Saprolegniasis

目的:以珍珠健康养殖水体底泥为材料分离放线菌,筛选对水产动物水霉病病原菌有抗菌活性的放线菌。方法:采用稀释涂布法,选用萘啶酮酸和放线菌酮双抗平板分离获得放线菌;以黄颡鱼和湘云鲫鱼卵水霉病原菌为靶标菌,采用琼脂块法测试所分离菌株抗水霉菌活性及其稳定性;对拮抗活性强的放线菌采用形态观察和16S r DNA序列分析进行分类鉴定。结果:从分离获得的27株放线菌中筛选出3株对水霉病原菌有拮抗活性的菌株QF1、DNC17和QHV2,其中QHV2抗菌活性与稳定性最好;形态学观察与16S r DNA序列分析结果表明QF1、DNC17和QHV2均属于链霉菌属(Streptomycete sp.),分别鉴定为Streptomyces diastatochromogenes、Streptomyces variabilis和Streptomyces collinus。结论:3株放线菌对水霉病原菌具有较好的拮抗活性,具有开发成抗水霉药物的潜在价值。

Objective： Isolation, screening and identification of antagonistic acfinomycetes against Saprolegniasis from the sediment in healthy aquaculture water of pearl： Methods： Using double resistant screen plate containing nalidixic acid and cycloheximide, dilution and spread plate method was applied to isolate actinomycetes. Taking pathogenic sapro- legnia isolated from the fish eggs of Pelteobagrus fulvidraco and Triploid crucian carp as test bacteria, Antimicrobial ac- tivity against saprolegnia and its stability were assessed using agar diffusion method. The isolates with high antimicrobial activity were identified by morphology and 16S rDNA gene sequence analysis. Results：3 strains of antagonistic actino- mycetes, named as QF1, DNC17, QHV2, were screened from the 27 actinomycetes which were isolated from the sedi-ment samples. Among the 3 isolates, QHV2 strain had the best antibacterial activity and stability. Based on morphology and 16S rDNA gene sequencing, QF1, DNC17 and QHV2 strains all belonged to the genus Streptomyces, and were iden- tified as Streptomyces diastatochromogenes, Streptomyces variabilis and Streptomyces collinus respectively. Conclusion： Taken together, the 3 isolated actinomycetes have higher antagonistic activity against saprolegnia, suggesting that they have potential value of the medicine development for the preventing and controlling of Saprolegniasis.