CELL CELL INTERACTION BETWEEN ORAL ACTINOMYCETES AND OTHER ORAL BACTERIA

我们研究计划的重点是了解 早期定殖细菌在细菌附着中的共聚集 清洁的牙齿表面。 最初的定殖者包括放线菌 和链球菌。 34.8kDa脂蛋白表面粘附素，ScaA， 来自戈登链球菌ATCC 51656的编码为2.5kb的 由三个基因组成的转录单位。 这个单位是一个 一种假定的ATP结合盒操纵子，类似于编码 革兰氏阴性杆菌的结合蛋白依赖转运系统 细菌和结合脂蛋白依赖的运输系统 革兰氏阳性菌。 ScaA可能锚定在细胞中 膜通过其脂质部分，而其受体识别 结合位点暴露于环境中。 戈登链球菌DL 1中的两个聚集相关基因具有 通过转座子诱变和整合 诱变 通过对转座子侧翼的DNA进行测序， 发现与参与合成的基因有关， 脂磷壁酸，另一类表面分子。 序列 在红霉素插入质粒的侧翼与34- 来自枯草芽孢杆菌的kDa蛋白。 S. 戈登氏菌DL 1从其表面失去了100-kDa的蛋白质。 这 基因已被克隆，转化子恢复了亲本 表型和100-kDa蛋白。 有人提出，蛋白质 是介导属内共聚集的粘附素。 血清型放线菌WVA 963菌株PK 1259仅表现出 与链球菌的乳糖分解性共聚集。 之一 自发共聚集缺陷突变体分离的排泄物a 95-已通过乳糖-琼脂糖亲和层析纯化的kDa蛋白 珠并通过与伴侣链球菌细胞结合。 抗血清 与乳糖-琼脂糖珠制备物结合阻断了 亲本放线菌与链球菌，这表明，95-kDa 蛋白质是介导这种共聚集的粘附素。 这些研究的长期目标总体上是阐明 负责细菌定植的分子机制 人类口腔生态系统

The focus of our research program is to understand the role of coaggregation in bacterial accretion of early colonizing bacteria on a clean tooth surface. The primary colonizers include actinomyces and streptococci. The 34.8-kDa lipoprotein surface-adhesin, ScaA, from Streptococcus gordonii ATCC 51656 is encoded as part of a 2.5 kb transcription unit consisting of three genes. This unit is a putative ATP-binding cassette operon similar to the operons encoding the binding-protein dependent transport systems of Gram-negative bacteria and the binding lipoprotein dependent transport systems of Gram-positive bacteria. ScaA probably is anchored in the cell membrane through its lipid moiety, while its receptor-recognizing binding site is exposed to the environment. Two coaggregation-relevant genes in Streptococcus gordonii DL1 have been identified by transposon mutagenesis and by integrative mutagenesis. By sequencing the DNA flanking the transposon, a close relationship was found to genes involved with synthesis of lipoteichoic acids, another class of surface molecules. The sequence flanking the erythromycin insertion plasmid is 56% identical to a 34- kDa protein from Bacillus subtilis. The insertion mutants of S. gordonii DL1 have lost a 100-kDa protein from their surface. This gene has been cloned and transformants regained the parental phenotype and the 100-kDa protein. It is proposed that the protein is an adhesin mediating intrageneric coaggregation. Actinomyces serovar WVA963 strain PK1259 exhibits only lactose-inhibitable coaggregation with streptococci. One of the spontaneous coaggregation defective mutants isolated excretes a 95-kDa protein that has been purified by lactose-agarose affinity beads and by binding to the partner streptococcal cells. Antiserum to the lactose-agarose bead preparation blocks coaggregation of the parent actinomyces with streptococci, suggesting that the 95-kDa protein is the adhesin mediating this coaggregation. The long range goal of these studies, collectively, is to elucidate the molecular mechanisms responsible for bacterial colonization in the human oral ecosystem.