弧菌拮抗菌的筛选

用平板划线或点种法对 6 0 2株海洋细菌进行筛选 ,得到 4株对海水养殖动物 (鱼、虾、贝 )的病原菌有拮抗作用的细菌。并对拮抗菌 QJ2的拮抗作用进行了研究 ,结果为 :QJ2有广泛的弧菌抗菌谱 ,对 37株弧菌的抗菌阳性率达到 89.2 % (33/ 37) ;用活菌平板计数法和 O.D.60 0 nm研究了QJ2培养物的去细胞上清液 (CFS)与病原菌 W- 1的作用动力学 ,15min时 W- 1的细菌数便开始减少 ,4 h时细菌数最少 ,6 h后开始增加 ,而对照组的细菌数呈逐渐上升趋势 ;QJ2对自身的拮抗物质不敏感 ;QJ2抗性物质的分子量不大于 80 0 0 Da;经常规生理生化方法和 API- 2 0细菌快速鉴定系统鉴定 ,QJ2为气味黄杆菌 (Flavobacterium odoratum)。

Selection of Vibrios-Antagnism Bacteria

Four antagonistic bacteria were selected from 602 strain s bytheir inhibitory activities to 4 indicating vibrios. Evident clear zones or overlaying zones were observed around the selected bacteria by dot or scratch- inoculating method. Strain QJ2 had a wide antibacterial spectrum and was able to inhibit 33 vibrios among 37. Study of kinetic antibacterial activities of QJ2 a gainst pathogen W-1 was tested by viable bacteria counts and absorbency at 600n m: 106～107 cfu/mL cells of W-1 began to decrease in 15 min after mixing with CFS(cell free-supernatant) of QJ2; the bacterial counts decreased to a min imum at 4h, and the numbers of bacteria began to increase after 6h. The cells of QJ2 did not show any sensitivity to its inhibitory substances in CFS. The size of active molecule in the CFS of QJ2 was smaller than 8000 Da by measuring the i nhibitory activities of the fluid inside and outside the dialysis cellulose tubi ng. QJ2 was identified as Flavobacterium ordaratum by traditional morphologi cal and biochemical method and API-20 identification system.