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 粘附和细胞信号转导。 口腔链球菌 和放线菌形成大多数革兰氏阳性的早期殖民者在一个 清洁牙齿表面。 主要革兰氏阴性菌为梭杆菌属 核质 这些组的每一个成员和其他13个属的口头 检测细菌与幽门螺杆菌结合的能力， 慢性胃炎的主要致病因素。 只有F.具核 承认H。幽门螺杆菌;相互作用是由乳糖： 梭菌细胞似乎具有粘附素，而螺旋藻细胞似乎具有粘附素。 表达相应的受体。 这些结果证实了 牙菌斑可能是这种病原体的储存库 在胃的外面。 戈登链球菌DL 1的粘附相关sca操纵子含有 三个基因 通过与其他ATP结合盒的序列同源性 小分子转运系统，基因产物是ATP酶， 疏水膜蛋白和底物结合脂蛋白。 在编码ATP酶（scaC）和ATP酶的基因中插入突变， 底物结合脂蛋白（scaA）导致细胞生长受损 在含有<0.5 μ M Mn ~（2+）的培养基中，54 Mn ~（2+）摄取抑制>70%。 低浓度Mn ~（2+）（<0.5mg/L）可诱导ScaA脂蛋白的产生 μ M）和通过添加=20 μ M Zn 2+。 ScaA是一种高亲和力结合蛋白， 脂蛋白用于获得Mn 2+，并且是生长必需的。 在Mn 2+限制条件下的链球菌，如在口腔中发现的 腔 S.戈登氏菌DL 1和其他遗传上不同的链球菌参与 在乳糖可降解的细胞间相互作用中， 共聚合一个转座子插入突变体被确定为失败， 表现出乳糖可降解的属内聚集，但仍 能与放线菌进行其它属间的共聚合。 一个6.5kb的 含有转座子插入位点的区域靠近5'端， 测序并包含与蛋白质的序列同源性， 运输二糖乳糖和纤维二糖。 这些结果表明 乳糖降解的属内聚集可能是由 通过双重功能的表面蛋白质也运输二糖。 这些研究的长期目标是共同阐明 细菌之间相互作用的分子机制， 殖民人类口腔生态系统。 我们的目的是扩大研究 细胞与细胞的接触，包括基因表达后， 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.