水产学报2018，Vol.42Issue(2)：291-302,12.DOI:10.11964/jfc.20170110680
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(Oreochromis niloticus) and their effects on capsular sialic acid content and bacterial pathogenicity
摘要
Abstract
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 sialic acid con-tent and bacterial pathogenicity, capsular polysaccharide synthetic genecpsE,cpsK andneuA of GBS from O. niloticus 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 O. niloticusinfec-ted with GBS cultured at different temperature was analyzed by artificial challenge test. The results showed that amino acid sequence analysis encoded bycpsE,cpsK andneuA of GBS had conservative enzyme active sites which were essential for the synthesis of capsular polysaccharide.CpsE and NeuA of GBS isolated from O. nilotic-us shared high homology with those of GBS isolated from human and other fish species (>97％). The identities of cpsK of GBS isolated fromO. niloticus 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 sialic 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 con-tent of GBS cultivated at low temperature may provide protection for it to stay in the host. However, the expres-sions of some important virulence factors besides capsular sialic acid might be necessary for a strong bacteria pathogenicity for GBS cultivated at higher temperature.关键词
尼罗罗非鱼/无乳链球菌(GBS)/温度/荚膜多糖合成基因/荚膜唾液酸/致病力Key words
Oreochromis niloticus/Streptococcus agalactiae/temperature/capsular polysaccharide synthetic gene/capsular sialic acid/pathogenicity分类
生物科学引用本文复制引用
师红亚,董浚键,张德锋,孙成飞,田园园,卢迈新,叶星..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[J].水产学报,2018,42(2):291-302,12.基金项目
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(2017HY-ZC06) （2017HY-ZC06）
国家自然科学基金(31272688) （31272688）
现代农业产业技术体系建设专项(CARS-46) Central Public-interest Scientific Institution Basal Research Fund, CAFS (2017HY-ZC06) （CARS-46）
National Natural Science Foundation of China (NSFC) (31272688) （NSFC）
China Agriculture Research System (CARS-46) （CARS-46）
