中国农业科学 ›› 2020, Vol. 53 ›› Issue (3): 658-668.doi: 10.3864/j.issn.0578-1752.2020.03.016

• 畜牧·兽医·资源昆虫 • 上一篇    

多杀性巴氏杆菌荚膜的生物合成及其调控机制研究进展

关丽君1,薛云1,丁文文1,赵战勤1,2()   

  1. 1 河南科技大学动物科技学院兽医生物制品工程实验室,河南洛阳 471003
    2 河南科技大学动物科技学院/河南省高等学校环境与 畜产品安全重点学科开放实验室,河南洛阳 471003
  • 收稿日期:2018-09-03 接受日期:2019-11-05 出版日期:2020-02-01 发布日期:2020-02-13
  • 通讯作者: 赵战勤
  • 作者简介:关丽君,E-mail:gljguanlijun@163.com。
  • 基金资助:
    国家自然科学基金项目(31302106);国家自然科学基金项目(U1704117);国家自然科学基金项目(31672530)

Advances in Mechanisms of Biosynthesis and Regulation of Pasteurella multocida Capsule

GUAN LiJun1,XUE Yun1,DING WenWen1,ZHAO ZhanQin1,2()   

  1. 1 Laboratory of Veterinary Biologics Engineering, College of Animal Science and Technology, Henan University of Science and Technology, Luoyang 471003, Henan
    2 College of Animal Science and Technology, Henan University of Science and Technology/ Key-Disciplines Laboratory of Safety of Environment and Animal Product, Luoyang 471003, Henan
  • Received:2018-09-03 Accepted:2019-11-05 Online:2020-02-01 Published:2020-02-13
  • Contact: ZhanQin ZHAO

摘要:

多杀性巴氏杆菌可广泛感染多种动物,引起出血性败血症或传染性肺炎。多杀性巴氏杆菌的细胞表面具有一层黏液样的荚膜多糖,是其重要的结构成分和毒力因子,在细菌与宿主的相互作用中起到重要作用,促进细菌粘附于宿主表面,增强细菌的毒力。多杀性巴氏杆菌荚膜的分子结构与脊椎动物的糖胺聚糖(GAG)相似,都由重复的二糖单元聚合形成线性多糖链,这是该菌在感染宿主过程中进行分子伪装、抵抗吞噬和发生免疫逃逸的重要免疫学物质基础。近年来,在多杀性巴氏杆菌荚膜的生物合成及其调控机制方面取得了一系列重要的研究进展,为多杀性巴氏杆菌荚膜的分子致病机理研究提供了一定的基础知识,为多杀性巴氏杆菌荚膜多糖疫苗的研发提供了理论依据。文章系统阐述了多杀性巴氏杆菌荚膜的生物合成途径及其表达调控机制,主要包括荚膜的血清分型、荚膜多糖的成分与结构、荚膜的生物合成基因簇与功能、荚膜多糖的分子合成机制、荚膜生物合成基因簇的表达调控机制,共5个方面。依据荚膜抗原,多杀性巴氏杆菌可分为A、B、D、E、F共5种荚膜血清型。A型荚膜GAG成分是透明质酸、D型是肝素、F型是软骨素,分别由其相应的二糖单元[β-葡糖醛酸/β-乙酰葡糖胺]、[β-葡糖醛酸/α-乙酰葡糖胺]、[β-葡糖醛酸/β-乙酰半乳糖胺]重复构成;B型荚膜多糖是由阿拉伯糖、甘露糖和半乳糖以某种结构形式聚合而成,E型荚膜多糖的成分与化学结构尚不确定。多杀性巴氏杆菌A型、B型、D型、E型和F型荚膜多糖生物合成的相关基因以基因簇的形式存在,分为3个不同的功能区,R1、R2和R3;R1区负责转运荚膜多糖,R2区负责单糖的活化和荚膜多糖的组装,R3区负责荚膜多糖的修饰(磷脂替换);根据R2区结构和基因数量的不同又可将5种荚膜的生物合成基因簇分为两类:A型、D型、F型为I类,R2区含有4个基因;B型和E型为II类,R2区含有9个基因,且利用R2区特异性基因设计引物,可以通过PCR方法快速鉴定多杀性巴氏杆菌的荚膜血清型。多杀性巴氏杆菌的荚膜GAG在细胞质中生成,由R1区编码蛋白所形成的ABC转运体输出至细胞表面,末端糖脂通过分子间氢键与细胞壁紧密结合,形成菌体表面的粘液状荚膜;在多杀性巴氏杆菌荚膜GAG的生物合成过程中,位于R2区的糖基转移酶基因决定了活化单糖的种类和组装后荚膜多糖的类型。在多杀性巴氏杆菌荚膜的生物合成基因簇中,R1和R2区形成一个操纵子,转录方向一致,而R3转录方向与其相反,两者的启动子区域均位于R2和R3区域之间的DNA序列上;多杀性巴氏杆菌荚膜生物合成基因簇的转录过程受Fis蛋白正向调控,翻译过程主要受Hfq蛋白正向调节。

关键词: 多杀性巴氏杆菌, 荚膜, 糖胺聚糖, 生物合成, 表达调控

Abstract:

Pasteurella multocida can be widely infected with a variety of animals, causing hemorrhagic septicemia or infectious pneumonia. P. multocida possess a viscous capsular polysaccharide on the cell surface, which is a critical structural component and virulence factor, and plays an important role in the interaction between bacteria and the host, promoting the adhesion of bacteria to the host surface and enhancing the virulence of the bacteria. The molecular structure of the P. multocida capsule is similar to that of vertebrate glycosaminoglycan, which is polymerized by repeated disaccharide units to form a linear polysaccharide chain, which is an important immunological material basis for molecular mimicry, resistance to phagocytosis, and immune evasion during the infection of the host. In recent years, a series of important research advances have been made in the biosynthesis and regulation mechanism aspects of P. multocida capsule, providing a certain basic knowledge for the molecular pathogenesis of P. multocida capsule, and supplying a theoretical basis for the development of the capsular polysaccharide vaccine of P. multocida. This paper systematically illuminates the biosynthesis and expression regulation mechanisms of P. multocida capsule, including the serotyping of the capsule, the composition and structure of the capsular polysaccharide, the biosynthesis gene cluster and function of the capsule, the molecular synthesis mechanism of capsular polysaccharide, the expression regulation mechanism of capsular biosynthesis gene cluster, a total of five aspects. According to the capsular antigen, P. multocida is divided into five capsular serogroups of A, B, D, E, and F. The type A capsule GAG component is hyaluronic acid; the type D is heparosan; the type F is chondroitin, which is repeatedly composed of its corresponding disaccharide unit [β-GlcUA/β-GlcNAc], [β-GlcUA/α-GlcNAc], [β-GlcUA/β-GalNAc], respectively; the type B capsular polysaccharide is composed of arabinose, mannose and galactose in a certain structural form, and the composition and chemical structure of type E capsular polysaccharide are uncertain. Genes related to the biosynthesis of A, B, D, E and F capsules of P. multocida exist in the form of gene clusters and are divided into three distinct functional regions, R1, R2 and R3; the R1 region is responsible for transporting the capsular polysaccharide, the R2 region is responsible for the activation of the monosaccharide and the assembly of the capsular polysaccharide, and the R3 region is responsible for the modification of capsular polysaccharide (phospholipid replacement); according to the structure and the number of genes of the R2 region, the biosynthetic gene clusters of the five capsules can be divided into two categories: type A, D and F are Class I, and R2 contains 4 genes; types B and E are Class II, and R2 contains 9 genes, and using the specific gene in the R2 region to design primers, the capsular serotype of P. multocida can be rapidly identified by PCR. The capsular GAG of P. multocida is synthesized in the cytoplasm, and then exported to the cell surface via the ABC transporter formed by the protein encoded by the R1 region, and tightly bound to the cell surface by covalent attachment to the phospholipid; during the biosynthesis of the P. multocida capsular GAG, the glycosyltransferase gene located in the R2 region determines the type of activated monosaccharide and the type of capsular polysaccharide after assembly. In the biosynthetic gene cluster of the P. multocida capsule, the R1 and R2 regions form an operon with the same transcriptional direction, while the R3 transcription direction is opposite, and the promoter regions of both are located on the DNA sequence between the R2 and R3 regions; the transcriptional process of the P. multocida capsular biosynthesis gene cluster is positive regulated by the Fis protein, and the translation process is mainly positive regulated by Hfq protein.

Key words: Pasteurella multocida, capsule, glycosaminoglycan, biosynthesis, expression regulation