一株增强中华绒螯蟹抗病力的固氮红细菌SY5的分离鉴定与表征

Isolation,Identification and Characterization of Rhodobacter azotoformans SY5 with Enhancing Effect on the Disease Resistance of Eriocheir sinensis

为丰富在中华绒螯蟹病害防控中具有潜在应用价值的微生物资源,以类胡萝卜素产生能力作为评价指标,从养殖池底泥中分离获得一株优良的好氧光合细菌SY5,在形态与生理生化鉴定以及分子鉴定的基础上对其进行药敏特性分析,并进一步评价了其对中华绒螯蟹抗弗氏柠檬酸杆菌感染的保护效果。结果表明,菌株SY5为固氮红细菌(Rhodobacter azotoformans),革兰氏染色阴性,在营养琼脂平板上的菌落特征为深红色、圆形、边缘整齐、光滑、湿润,与固氮红细菌YLK20的亲缘关系最近,对阿莫西林、新霉素、庆大霉素、四环素、多黏菌素B、恩诺沙星、环丙沙星、卡那霉素、氨苄西林、罗红霉素、磷霉素、链霉素高度敏感,对多西环素中度敏感;在饲料中添加终浓度为(6.0×10^(5))-(6.0×10^(9))CFU/g时对中华绒螯蟹抗弗氏柠檬酸杆菌感染的有效保护率为60.0%-100%。这些研究结果为固氮红细菌SY5作为中华绒螯蟹养殖用饲料添加剂的后期开发奠定了基础。

In order to enrich microbial resources with the potential application in the prevention and control of diseases in Eriocheir sinensis,strain SY5 of aerobic photosynthetic bacterium was isolated from the sediment of culture pond with carotenoid production ability as the evaluation index,was identified based on morphological,biochemical and molecular identification,and its antibiotic susceptibility and protective effect on E.sinensis against Citrobacter freundii infection were further evaluated.The results indicated that the SY5 isolate was identified phenotypically and molecularly as Rhodobacter azotoformans.It was Gram negative,formed colonies with the characteristics of dark red,round,smooth,moist and regular-edged on nutrient agar plate,showed the closest genetic relationship with R.azotoformans YLK20,and demonstrated highly sensitive to amoxicillin,neomycin,gentamicin,tetracycline,polymyxin B,enrofloxacin,ciprofloxacin,kanamycin,ampicillin,roxithromycin,fosfomycin,streptomycin and moderately sensitive to doxycycline.Besides,it demonstrated effective protection rates of 60.0% to 100% at final doses of 6.0×10^(5) to 6.0×10^(9) CFU/g diets against C.freundi infection in E.sinensis.These data lays a foundation for the later development of R.azotoformans SY5 as a feed additive for E.sinensis aquaculture.