Characterization of a novel S. aureus biofilm polysaccharide

摘要 金黄色葡萄球菌是一种重要的人类病原体，可导致多种疾病，其中一些 很严重，很难治疗。目前的治疗方法很大程度上局限于抗生素治疗。然而，S. 金黄色葡萄球菌能够在植入物或组织上形成生物膜，使细菌对抗生素和 无需获得遗传抗性特征的宿主免疫防御系统。因此，生物膜的形成往往会导致 治疗失败。生物膜是由包裹在其中的多层细菌细胞组成的细菌群落。 一种使细菌保持在生物膜结构内的细胞外基质。迄今为止，葡萄球菌生物膜基质 已被证明由多糖、蛋白质和胞外DNA组成，但其组成尚未被 完全定义好了。因此，了解生物膜基质的组成是揭示生物膜形成机制的关键 并为治疗或诊断开发提供潜在的靶点。不同的生物膜基质蛋白有 已有报道，但仅有极少数几种基质多糖被鉴定出来。我们已经证明了 沙门氏菌中一个先前未描述的多糖合成基因簇的突变。 金黄色葡萄球菌基因组减少了生物膜的形成。这些结果表明，该基因簇参与了 一种新的多糖的产生，它通过促进生物膜的形成来促进金黄色葡萄球菌的毒力。 因此，本应用的目的是验证和研究这种新型的多糖。为此，我们将在分子水平上 鉴定基因簇，生化鉴定目标1中的新多糖，并研究其作用 在目标2中，在种植体骨感染模型中，该多糖在生物被膜形成和毒力方面的作用。

Summary Staphylocuccus aureus is a significant human pathogen that causes a wide range of diseases, some of which are serious and difficult to treat. Current treatment methods are largely limited to antibiotic therapy. However, S. aureus is capable of forming biofilm on implants or tissues rendering the bacteria resistance to antibiotics and to host immune defense system without acqiuring genetic resistance traits. Thus, biofilm formation often leads to treament failures. Biofilms are bacterial communities consist of multiple layers of bacterial cells encased within an extracellular matrix that keeps the bacteria within the biofilm structure. To date, staphylococcal biofilm matrix has been shown to consist of polysaccharides, proteins and extracellular DNA but the composition is not been fully defined. Understanding biofilm matrix composition is therefore critical to unveil biofilm formaiton mechanism and provide potential targets for therapeutic or diagnostic development. Diverse biofilm matrix proteins have been reported but only very few species of matrix polysaccharide have been identified. We have shown that mutations in an previously uncharacterized gene cluster of putative polysaccharide sythesis genes in the S. aureus genome reduced biofilm formation. These results indicate that the gene cluster is involved in the production of a novel polysaccharide, which contributes to S. aureus virulence by promoting biofilm formation. Thus, the goal of this application is to verify and study this novel polysaccharide. To this end, we will molecularly characterize the gene cluster and biochemically identify the novel polysaccharide in Aim 1 and study the role of this polysacharide in biofilm formation and in virulence in an implant bone infection model in Aim 2.