革兰氏阳性菌荚膜多糖研究进展*

细菌的荚膜多糖是生物膜的重要组成部分,在细菌的生长分裂、维持细胞壁形态、抵御外界环境以及免疫反应等方面都起到重要作用。在致病菌中,荚膜多糖常作为一种毒力因子发挥作用。在革兰氏阳性菌中,荚膜多糖的化学结构、生物合成过程及功能应用越来越受到关注。讨论了革兰氏阳性菌中部分致病菌的荚膜多糖与非致病菌表面多糖的分布位置、化学组成及其结构特异性。重点讨论三种具有代表性的革兰氏阳性致病菌及非致病菌株:肺炎链球菌(Streptococcus pneumonia)、金黄色葡萄球菌(Staphylococcus aureus)及乳酸乳球菌(Lactococcus lactis)。综述革兰氏阳性菌中荚膜多糖生物合成的三种方式:Wzx/Wzy-依赖通路、ABC转运蛋白(ABC transporter)途径及合酶依赖途径,并举例解释了相应多糖的合成过程及相关基因。介绍了革兰氏阳性菌荚膜多糖及表面多糖的生理功能,如屏障保护功能、胞间黏附功能以及参与宿主细胞的免疫反应等。结合荚膜多糖的生物学功能,概述其当前主要研究进展,如构建高耐受工程菌疫苗研制等。结合细菌荚膜多糖的特征差异,对其在医药与工业生产领域的广阔前景提出展望和建议。

Research Progress of Capsular Polysaccharides in Gram-positive Bacteria

The capsular polysaccharide (CPS) of bacteria is an important part of bacterial biofilm. It plays an essential role in the bacterial growth and division. In the meantime, this structure is related to the cell wall morphology, bacterial resistance to the external environment and immune response. In pathogenic bacteria, capsular polysaccharides act as virulence factors, so they have been studied extensively. In gram-positive bacteria, the chemical structure, biosynthesis process and functional application of capsular polysaccharides have been paid more and more attention. In this paper, the chemical structure, synthesis pathway, function and application of CPS in gram-positive bacteria were reviewed. Firstly, the bacterial distribution, chemical composition and structural specificity of the CPS from the pathogenic and non-pathogenic strains were discussed. The discussion focused on three representative Gram-positive pathogenic and non-pathogenic strains: Streptococcus pneumonia, Staphylococcus aureus, and Lactococcus lactis. Next, three main ways of the capsular polysaccharides biosynthesis in Gram-positive bacteria were reviewed: Wzx/Wzy-dependent pathway, ABC transporter pathway and synthase dependent pathway. The synthesis process and related genes of the corresponding polysaccharides were explained with examples. The physiological functions of the capsular and surface polysaccharides in gram-positive bacteria were introduced, such as barrier protection, intercellular adhesion, and participation in the immune response of host cells. In combination with the biological functions of CPS, the research progress of main applications was summarized, such as the construction of high tolerance engineering strains and the development of vaccines. Due to the differences in the characteristics of capsular polysaccharides, their chemical structure and synthesis regulation are still not clear. Finally, combined with the broad prospects in pharmaceutical research and industrial production, the prospects and suggestions are provided for the future research of bacterial capsular polysaccharides.