Sialic acid mediated interbacterial adhesion among oral bacteria

项目总结/摘要 聚糖介导的细菌间共粘附是人类口腔中多物种生物膜形成的关键部分。 某些口腔链球菌菌株表达与唾液酸结合的富含丝氨酸的重复蛋白（SRRP）粘附素， 在人口腔粘膜上皮细胞和糖基化唾液蛋白上表达的常见末端糖。唾液 酸（Sias）是一组九碳糖，其中存在超过五十种不同的亚型。链球菌SRRP 在菌株之间具有遗传多样性，这些菌株可能进化为与众多Sia亚型结合。以确定 对于链球菌编码的多种Sia结合SRRP序列的全部范围，申请人使用了隐藏的 马尔可夫模型旨在识别六千多个公开可用的链球菌中的Sia结合SRRP 基因组序列申请人鉴定了数百个Sia结合SRRP序列，其可能反映了 不同Sia亚型的结合特异性。例如，口腔链球菌的几种菌株优选 结合两种Sia亚型，N-乙酰神经氨酸（Neu 5Ac）或N-羟乙酰神经氨酸（Neu 5Gc）中的任一种。 某些细菌菌株进化为从头合成或从环境中合成， 将它们显示在表面上。由于Sia亚型多种多样，而且申请人的数据显示， 链球菌Sia-结合SRRP序列同样多样，我们认为Sia-亚型- 介导的链球菌结合扩展超出Neu 5Ac和Neu 5Gc之间的单纯差异。我们一起努力， 这些数据作为申请人提出其独立假设的基础， 与其他口腔细菌表达的Sia亚型的分类结合。在这个项目中，申请人的目标是 鉴定作为Sia结合口腔链球菌共粘附伴侣的表达Sia的口腔细菌。在 目的1、通过计算机模拟方法鉴定表达Sia的口腔细菌，并从人口腔中分离Sia表达的细菌， 生物膜，然后测试与Sia结合的口腔链球菌的共粘附。在目标2中，已知 表达Sias以及Aim 1中新鉴定的菌株将用于确定Sia 由细菌表达的亚型影响共粘附。这项调查的结果将证明， Sia亚型如何影响聚糖介导的细菌间共粘附。研究的精确机制 Sia亚型介导的细菌间结合将有助于了解口腔微生物组成员如何相互作用 从而在人口腔中形成潜在的疾病相关微生物生物膜。计划中的项目将建立 Ahearn博士在生物信息学和实验分析博士论文研究期间获得的技能 细菌表面暴露的成分。在这个项目中，他将把他的专业知识扩展到新兴的领域， 微生物糖生物学从这个项目中获得的数据将使Ahearn博士能够进入他的下一阶段。 通过研究Sia和其他聚糖介导的共粘附在多物种口腔中的意义， 生物膜形成及其对人类口腔健康和全身性疾病的影响。

PROJECT SUMMARY/ABSTRACT Glycan-mediated interbacterial coadhesion is a critical part of multispecies biofilm formation in the human mouth. Certain strains of oral streptococci express serine-rich repeat protein (SRRP) adhesins that bind to sialic acids, common terminal sugars expressed on human oral mucosal epithelia and glycosylated salivary proteins. Sialic acids (Sias) are a group of nine-carbon sugars of which over fifty different subtypes exist. Streptococcal SRRPs are genetically diverse among strains, which likely evolved to bind to the multitude of Sia subtypes. To determine the full scope of diverse Sia-binding SRRP sequences encoded by streptococci, the applicant used hidden Markov models designed to identify Sia-binding SRRPs among over six thousand publicly available streptococcal genome sequences. The applicant identified hundreds of Sia-binding SRRP sequences, which likely reflect binding specificities for different Sia subtypes. For example, several strains of oral streptococci preferentially bind to either of the two Sia subtypes, N-acetylneuraminic acid (Neu5Ac) or N-glycolylneuraminic acid (Neu5Gc). Certain strains of bacteria evolved to either de novo synthesize or scavenge Sias from the environment and display them on their surface. Since Sia subtypes are diverse and since the applicant’s data show that streptococcal Sia-binding SRRP sequences are equally diverse, we believe that specificity of Sia-subtype- mediated streptococcal binding expands beyond the mere difference between Neu5Ac and Neu5Gc. Together, these data served as the basis for the applicant to formulate his independent hypothesis that oral streptococci bind to an assortment of Sia subtypes expressed by other oral bacteria. In this project, the applicant aims to identify Sia-expressing oral bacteria that serve as coadhesion partners of Sia-binding oral streptococci. In Aim 1, Sia-expressing oral bacteria will be identified by both an in-silico approach and isolated from human oral biofilms, then tested for coadhesion with Sia-binding oral streptococci. In Aim 2, bacterial strains known to express Sias as well as those newly identified strains in Aim 1 will be used to determine how different Sia subtypes expressed by bacteria affect coadhesion. The results of this proposed investigation will demonstrate how Sia subtypes influence glycan-mediated interbacterial coadhesion. Investigating the precise mechanism of Sia subtype-mediated interbacterial binding will help to understand how members of the oral microbiome interact to form potentially disease-associated microbial biofilms in the human oral cavity. The planned project will build on Dr. Ahearn’s skills acquired during his PhD dissertation research in bioinformatic and experimental analysis of bacterial surface-exposed components. In this project, he will expand his expertise into the emerging field of microbial glycobiology. Data derived from this project will allow Dr. Ahearn to advance to the next stage of his career by investigating the significance of Sia- and other glycan-mediated coadhesion during multispecies oral biofilm formation and its impact on both human oral health and systemic disease.