INRA, UMR1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France.
J Biol Chem. 2010 Apr 2;285(14):10464-71. doi: 10.1074/jbc.M109.082958. Epub 2010 Jan 27.
In Gram-positive bacteria, the functional role of surface polysaccharides (PS) that are not of capsular nature remains poorly understood. Here, we report the presence of a novel cell wall PS pellicle on the surface of Lactococcus lactis. Spontaneous PS-negative mutants were selected using semi-liquid growth conditions, and all mutations were mapped in a single chromosomal locus coding for PS biosynthesis. PS molecules were shown to be composed of hexasaccharide phosphate repeating units that are distinct from other bacterial PS. Using complementary atomic force and transmission electron microscopy techniques, we showed that the PS layer forms an outer pellicle surrounding the cell. Notably, we found that this cell wall layer confers a protective barrier against host phagocytosis by murine macrophages. Altogether, our results suggest that the PS pellicle could represent a new cell envelope structural component of Gram-positive bacteria.
在革兰氏阳性菌中，那些不属于荚膜性质的表面多糖（PS）的功能作用仍知之甚少。在这里，我们报告了乳球菌表面存在一种新型细胞壁 PS 菌膜。使用半液体生长条件筛选出自发 PS 阴性突变体，所有突变均定位于编码 PS 生物合成的单个染色体位置。PS 分子由六糖磷酸盐重复单元组成，与其他细菌 PS 不同。使用互补的原子力和透射电子显微镜技术，我们表明 PS 层形成了环绕细胞的外层菌膜。值得注意的是，我们发现这种细胞壁层赋予了细胞对宿主巨噬细胞吞噬作用的保护屏障。总的来说，我们的结果表明，PS 菌膜可能代表革兰氏阳性菌新的细胞包膜结构成分。
