Department of Microbiology, University of Alabama, Birmingham, Alabama 35294-2170, USA.
Annu Rev Microbiol. 2011;65:563-81. doi: 10.1146/annurev.micro.62.081307.162944.
Capsular polysaccharides and exopolysaccharides play critical roles in bacterial survival strategies, and they can have important medical and industrial applications. An immense variety of sugars and glycosidic linkages leads to an almost unlimited diversity of potential polysaccharide structures. This diversity is reflected in the large number of serologically and chemically distinct polysaccharides that have been identified among both gram-positive and gram-negative bacteria. Despite this diversity, however, the genetic loci and mechanisms responsible for polysaccharide biosynthesis exhibit conserved features and can be classified into a small number of groups. In Streptococcus pneumoniae, capsule synthesis occurs by one of two distinct mechanisms that involve the polymerization of either individual sugars in a processive reaction (synthase dependent) or discrete repeat units in a nonprocessive reaction (Wzy dependent). Characterization of these systems has provided novel insights that are applicable to polymers synthesized by many gram-positive and gram-negative bacteria, as well as eukaryotes.
荚膜多糖和胞外多糖在细菌生存策略中起着关键作用，它们具有重要的医学和工业应用价值。大量的糖和糖苷键连接导致潜在多糖结构的几乎无限多样性。这种多样性反映在已在革兰氏阳性和革兰氏阴性细菌中鉴定出的大量血清学和化学上不同的多糖上。然而，尽管存在这种多样性，但负责多糖生物合成的遗传基因座和机制具有保守的特征，可以分为少数几个组。在肺炎链球菌中，荚膜合成通过两种不同的机制之一发生，这两种机制涉及单个糖的聚合，或者在非连续反应中离散重复单元的聚合（依赖于 Wzy）。这些系统的表征提供了新的见解，这些见解适用于许多革兰氏阳性和革兰氏阴性细菌以及真核生物合成的聚合物。
