CELL CELL INTERACTION BETWEEN ORAL ACTINOMYCETES AND OTHER ORAL BACTERIA

我们研究计划的重点是了解细胞的作用 口腔生物膜中的黏附和细胞信号。口腔链球菌 和放线菌构成了大多数革兰氏阳性的早期定殖者 清洁牙齿表面。革兰氏阴性菌主要为梭杆菌 核糖体。其中每一组的成员和其他13个属的口腔 检测了细菌与幽门螺杆菌的结合能力， 慢性胃炎的主要致病因素。只有核盘藻 识别幽门螺杆菌；这种相互作用可被乳糖抑制： 梭菌细胞似乎具有粘附素，而螺旋杆菌则具有粘附素 表达了相应的受体。这些结果证明了 牙菌斑可能是这种病原体的宿主的观念 在胃之外。 戈登链球菌DL1的黏附相关SCA操纵子包含 三个基因。通过与其他ATP结合盒的序列同源性 小分子的运输系统，基因产物是一种ATPase， 疏水性膜蛋白和底物结合脂蛋白。 编码ATPase的基因(SCAC)和 底物结合脂蛋白(SCAA)导致细胞生长受阻 在含~lt；0.5um Mn2+和~gt；70%的培养液中，54Mn2+的吸收受到70%的抑制。 低浓度胞外Mn2+(&lt；0.5)诱导SCAA脂蛋白的产生 以及添加=20微米的锌离子。SCAA是一种高亲和力的结合 脂蛋白是获取Mn2+的主要物质，是细菌生长所必需的 与口腔中发现的链球菌在锰离子限制条件下的情况 空洞。 戈登氏链球菌DL1和其他遗传上不同的链球菌参与 在乳糖可抑制的细胞间相互作用中称为属内 聚合体。鉴定出一个失败的转座子插入突变体 表现出乳糖抑制的属内共聚体，但仍 能够与放线菌进行其他属间的共聚。A 6.5-KB 包含转座子插入位点的区域位于5‘端附近 测序并包含与参与蛋白的序列同源性 二糖、乳糖和纤维二糖的运输。这些结果表明 乳糖可抑制的属内共聚体可能是由 通过双功能表面蛋白也运输双糖。 总而言之，这些研究的长期目标是阐明 细菌间串扰的分子机制，因为它们 殖民人类口腔生态系统。我们的目的是扩大研究范围 细胞与细胞之间的接触，以包括基因表达后积累到 生物膜。

The focus of our research program is to understand the role of cell adherence and cell signaling in human oral biofilms. Oral streptococci and actinomyces form the majority of gram-positive early colonizers on a clean tooth surface. The major gram-negative bacterium is Fusobacterium nucleatum. Members of each of these groups and 13 other genera of oral bacteria were examined for their ability to bind to Helicobacter pylori, a major causative agent of chronic gastritis. Only F. nucleatum recognized H. pylori; the interaction was inhibitable by lactose: the fusobacterial cell appeared to possess the adhesin, while the helicobacter expressed a corresponding receptor. These results give credence to the notion that dental plaque may serve as a reservoir for this pathogen outside of the stomach. The adherence-relevant sca operon of Streptococcus gordonii DL1 contains three genes. By sequence homologies with other ATP-binding cassette systems for transport of small molecules, the gene products are an ATPase, a hydrophobic membrane protein and a substrate-binding lipoprotein. Insertional mutations in the genes encoding the ATPase (scaC) and the substrate-binding lipoprotein (scaA) resulted in impaired growth of cells in media containing <0.5 uM Mn2+ and >70% inhibition of 54Mn2+ uptake. Production of ScaA lipoprotein was induced at low extracellular Mn2+ (<0.5 uM) and by addition of =20 uM Zn2+. ScaA is a high-affinity binding lipoprotein for acquisition of Mn2+ and is essential for growth of streptococci under Mn2+-limiting conditions like that found in the oral cavity. S. gordonii DL1 and other genetically distinct streptococci participate in lactose-inhibitable cell-to-cell interactions called intrageneric coaggregations. A transposon insertion mutant was identified that failed to exhibit lactose-inhibitable intrageneric coaggregations but remained capable of other intergeneric coaggregations with actinomyces. A 6.5-kb region containing the transposon insertion site near the 5' end was sequenced and contained sequence homologies to proteins involved in transport of disaccharides lactose and cellobiose. These results suggest that the lactose-inhibitable intrageneric coaggregations may be mediated by dual functional surface proteins that also transport disaccharides. The long range goal of these studies, collectively, is to elucidate the molecular mechanisms involved in cross talk among the bacteria as they colonize the human oral ecosystem. Our intention is to extend the studies of cell-to-cell contact to include gene expression after accretion into the biofilm.