尼罗罗非鱼无乳链球菌荚膜多糖合成基因的表达及其与荚膜唾液酸含量、菌株致病性的关系  

Expressions of capsular polysaccharide synthetic gene of Streptococcus agalactiae isolated from Nile tilapia, and their effects on capsular sialic acid content and bacterial pathogenicity

作　　者：师红亚 董浚键[1] 孙成飞[1] 田园园[1,2] 胡婕 叶星[1,2] SHI Hongya 1,2, DONG Junjian 1, SUN Chengfei 1, TIAN Yuanyuan 1,2, HU Jie 1, YE Xing 1,2(1 Key Laboratory of Tropical ＆ Subtropical Fisheries Resource Application ＆ Cultivation, Ministry of Agriculture, Pearl River Fisheries institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China; 2. College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China)

机构地区：[1]中国水产科学研究院珠江水产研究所、农业部热带亚热带水产资源利用与养殖重点实验室,广东广州510380 [2]上海海洋大学水产与生命学院,上海201306

出　　处：《珠江水产科学》2017年第4期1-13,共13页Finsheries Science and Technology Industry

基　　金：中国水产科学研究院中央级公益性科研院所基本科研业务费专项资金资助（2017HY-ZC06）;国家自然科学基金（NSFC）（31272688）;现代农业产业技术体系建设专项资助（CARS-48）

摘　　要：为了解尼罗罗非鱼无乳链球菌（GBS）荚膜多糖合成基因的表达及其与英膜唾液酸含量、菌株致病性的关系，本实验克隆了尼罗罗非鱼荚膜多糖合成基因epsE、cpsK和neuA，通过qPCR方法分析了这3个基因在不同培养温度下表达水平的变化，同时，通过比色法测定了不同培养温度下GBS荚膜唾液酸含量的变化，通过人工感染实验分析了不同水温条件下GBS对罗非鱼的致病性。结果显示，cpsE、cpsK和neuA编码的氨基酸序列均具有保守的与荚膜多糖合成相关的酶活性位点，CpsE、NeuA与已知鱼源GBS（Ia和Ib型）和人源GBS（Ia、Ib和II～IX型）相应序列的同源性均达到97％以上，而CpsK与鱼源、人源的序列同源性则分别为56％～100％和27％～100％。在不同培养温度下GBS、cpsK和neuA表达水平的变化与荚膜唾液酸含量的变化一致；在较高温度（28和34℃）下培养的GBS英膜唾液酸含量、菌株攻毒后罗非鱼的死亡率均随温度的升高而递增，而在22℃下培养的GBS唾液酸含量最高，攻毒后罗非鱼的死亡率却最低。该研究结果表明，GBSCpsK和NeuA在GBS荚膜多糖的唾液酸化中起重要作用，较低温度下GBS荚膜唾液酸的高含量有助于其在宿主体内的潜伏，而较高水温条件下细菌的强致病性可能还与除荚膜唾液酸外的某些重要的毒力因子的表达有关。In order to understand the expressions of capsular polysaccharide synthetic gene of Streptococcus agalactiae （GBS） isolated from Oreochromis niloticus （Nile tilapia）, and their effects on capsular sialie acid content and bacterial pathogenicity, capsular polysaccharide synthetic gene cpsE, cpsK and neuA of GBSfrom Nile tilapia were cloned in the study. The expression levels of these genes at different temperature were detected by qPCR. Capsular sialic acid content was detected by colorimetric method. The mortality rate of tilapia infected with GBS cultured at different temperature was analysed by artificial challenge test. The results showed that amino acid sequence analysis encoded by cpsE, cpsK and neuA of GBS had conservative enzyme active sites which were essential for the synthesis of capsular polysaccharide. CpsE and NeuA of GBS isolated from Nile tilapia shared high homology with those of GBS isolated from human and other fish species （〉97%）. The identityies of cpsK of GBS isolated from Nile tilapia with those of other fish species （serotype Ia and Ib） and human （serotype Ia, Ib and II - IX） were 56% - 100% and 27% - 100%, respectively. The expression levels of cpsK and neuA of GBS cultivated at different temperature were consistent with that of capsular sialic acid content. Capsular sialie acid content and the mortality rate of tilapia infected with GBS cultivated at 28 and 34℃ were increased with the rise of temperature. The mortality rate of tilapia after artificial challenge at 22℃ was the lowest though the highest capsular sialic acid content was observed. The research suggested that the expression levels of CpsK and NeuA played an important role in the process of sialylation of capsular polysaccharide. Higher capsular sialic acid content of GBS cultivated at low temperature may provide protection for it to stay in the host. However, the expressions of some important virulence factor besides capsular sialic acid might be necessary for a strong bacteria pathogenicity for GBS c

关 键 词：尼罗罗非鱼 无乳链球菌(GBS) 温度 荚膜多糖合成基因 唾液酸 致病力 

分 类 号：S965.125[农业科学—水产养殖]