A novel polar surface polysaccharide from Rhizobium leguminosarum binds host plant lectin
A novel polar surface polysaccharide from Rhizobium leguminosarum binds host plant lectin
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DOI：
10.1111/j.1365-2958.2006.05057.x
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发表时间：
2006-03-01
影响因子：
3.6
通讯作者：
Kijne, JW
中科院分区：
文献类型：
--
作者：
Laus, MC;Logman, TJ;Kijne, JW
根瘤菌产生不同的表面多糖，这些多糖要么分泌在生长介质中，要么形成细胞周围的胶囊。在这里，我们描述了从一株使豌豆(豌豆)和蚕豆(Vetch)根瘤形成根瘤的豆科根瘤菌中分离并部分表征一种新型的高相对分子质量的表面多糖。碳水化合物分析表明，该多糖由95%的甘露糖和葡萄糖组成，并含有少量的半乳糖和鼠李糖。凝集素沉淀分析表明，豌豆和豌豆凝集素与这种多糖的结合亲和力很高，与该菌株的其他已知的荚膜和胞外多糖形成了鲜明的对比。该多糖的表达不依赖于Sym质粒或NOD基因诱导子柚皮苷元的存在。用标记的豌豆凝集素与豆类红假单胞菌孵育，结果表明该多糖仅定位于细菌细胞的一极。与根瘤菌和标记的豌豆凝集素一起培养的豌豆根显示，这种细菌极参与了根表面的附着。与弱碱性条件下的情况相反，在弱酸性条件下，缺乏这种多糖生产的突变株在附着和根毛侵染方面受到损害。我们的数据与这样的假设是一致的，即根瘤菌可以使用(至少)两种机制在根表面停靠，在微酸性条件下使用凝集素-葡聚糖机制。
Rhizobium bacteria produce different surface polysaccharides which are either secreted in the growth medium or contribute to a capsule surrounding the cell. Here, we describe isolation and partial characterization of a novel high molecular weight surface polysaccharide from a strain of Rhizobium leguminosarum that nodulates Pisum sativum (pea) and Vicia sativa (vetch) roots. Carbohydrate analysis showed that the polysaccharide consists for 95% of mannose and glucose, with minor amounts of galactose and rhamnose. Lectin precipitation analysis revealed high binding affinity of pea and vetch lectin for this polysaccharide, in contrast to the other known capsular and extracellular polysaccharides of this strain. Expression of the polysaccharide was independent of the presence of a Sym plasmid or the nod gene inducer naringenin. Incubation of R. leguminosarum with labelled pea lectin showed that this polysaccharide is exclusively localized on one of the poles of the bacterial cell. Vetch roots incubated with rhizobia and labelled pea lectin revealed that this bacterial pole is involved in attachment to the root surface. A mutant strain deficient in the production of this polysaccharide was impaired in attachment and root hair infection under slightly acidic conditions, in contrast to the situation at slightly alkaline conditions. Our data are consistent with the hypothesis that rhizobia can use (at least) two mechanisms for docking at the root surface, with use of a lectin-glycan mechanism under slightly acidic conditions.