磷壁酸(teichoic)
G+ 菌的细胞壁较厚（20~80nm），除含有15~50层肽聚糖结构外，大多数还含有大量的磷壁酸（teichoic acid），少数为磷壁醛酸（teichuronic acid），约占细胞壁干重的 50%。
Most Gram-positive cell walls contain considerable amounts of teichoic and teichuronic acids, which may account for up to 50% of the dry weight of the wall and 10% of the dry weight of the total cell. In addition, some Gram-positive walls may contain polysaccharide molecules.
化学成分
- 核糖醇型
- 甘油型
磷壁酸是核糖醇（ribitol）或甘油残基经磷酸二酯键连接成的链状多聚物，穿插于肽聚糖层中，其结构中少数基团被氨基酸或糖所取代，多个磷壁酸分子组成长链穿插于肽聚糖层中，这是细菌细胞带负电荷的重要物质基础。
磷壁酸按其结合部位不同，分
- 壁磷壁酸（wall teichoic acid, WTA）
- 一端通过磷脂与肽聚糖上的胞壁酸共价结合，另一端伸出细胞壁游离于外。
- 膜磷壁酸（membrane teichoic acid）/称脂磷壁酸（Lipoteichoic acid, LTA）
- 一端与细胞膜外层的糖脂共价结合，另一端穿过肽聚糖层伸出细胞壁表面呈游离状态。
磷壁醛酸与磷壁酸相似，仅其结构中以糖醛酸代替磷酸。
壁磷壁酸与脂磷壁酸共同组成带负电荷的网状多聚物或基质，使得G+ 菌的细胞壁具有良好的坚韧性、通透性及静电性能。磷壁酸具有抗原性及黏附素活性。
结合部位
- 膜磷壁酸（）
- 壁磷壁酸 （连接在肽聚糖上）
特点
- 带有较多的负电荷
- 表面抗原
- 参与黏附
相关
Their activity is often increased, however, by partial digestion of the peptidoglycan; thus, much of the teichoic acid may lie between the cytoplasmic membrane and the peptidoglycan layer, possibly extending upward through pores in the latter (Figure 2-18B). In the pneumococcus (Streptococcus pneumoniae), the teichoic acids bear the antigenic determinants called Forssman antigen. In Streptococcus pyogenes, LTA is associated with the M protein that protrudes from the cell membrane through the peptidoglycan layer. The long M protein molecules together with the LTA form microfibrils that facilitate the attachment of S. pyogenes to animal cells (see Chapter 14).
The teichuronic acids are similar polymers, but the repeat units include sugar acids (eg, N-acetylmannosuronic or d-glucosuronic acid) instead of phosphoric acids. They are synthesized in place of teichoic acids when phosphate is limiting.