Studies on mechanism of interbacterial aggregation of Bacteroides gingivalis with oral streptococci

牙龈拟杆菌可能在牙周病的病因和发病机制中起重要作用。研究表明，牙龈假单胞菌具有聚集口腔链球菌的粘附性，其能力可能与其在牙周袋中的定植有关。牙龈假单胞菌的血凝活性也被作为衡量该菌与其他细胞粘附性的参数之一。采用超速离心、SepharoseCL-4B凝胶过滤和精氨酸-琼脂糖亲和层析的方法，从细菌结合粘附素(HA)中分离得到血凝素。血凝抑制实验表明，L精氨酸和含有精氨酸的多肽对该酶有抑制作用，但不受受试糖类的影响。BBA的纯化程序与HA相同，BBA的活性与HA的活性在一定程度上一致。纯化的BBA等电点为4.0。按干重计算，BBA含有81%的蛋白质和8%的中性碳水化合物，但没有检测到低于1%的脂多糖和核酸。BBA拥有三个主要的蛋白质亚基，相对分子质量约为24,000，37,000和44,000。通过BBA的电子显微照片，从未观察到类似于菌毛的结构。精氨酸和含精氨酸的多肽对BBA活性也有抑制作用。这些结果表明，精氨酸可能是BBA与链球菌在聚集过程中的接触残基。

Bacteroides gingivalis may play an important role in the etiology and pathogenesis of periodontal disease. It has been shown that B. gingivalis possesses adhesive properties enabeling to aggregate oral streptococci, and its ability may be assosiated with the colonization of the organisms in the periodontal pocket. Hemagglutinating activity of B. gingivalis has been also studied as one of the parameters that the adherence of this organisms to the others cells. This study deals with the purification and characterization of bacterial binding adhesin from B. gingivalis 381(BBA).The hemagglutinin(HA) was isolated from the culture fluid by ultracentrifugation followed by a gel filtration on Sepharose CL-4B and by an affinity chromatography on arginine-agarose with triton X-100. Hemagglutination inhibition experiments showed that the activity was inhibited by L-arginine and the arginine-containing peptides, although the activity was unaffected by the sugars tested. The purification of the BBA was performed by the same procedures of the HA and the activity of BBA coincided in fractions with that of HA. The isoelectric point of the purified BBA was 4.0. It was found that the BBA contained 81% protein and 8% neutral carbohydrate but no detectable lipopolysaccharide and nucleic acid in quantities of less than 1% by calculation based on dry weight. The BBA possessed three major subunits of protein with MWs of about 24,000, 37,000 and 44,000. By electron micrographs of the BBA, the structures resembling fimbriae were never observed. The BBA activity was also inhibited by arginine and arginine-containing peptides especifically. These results suggest that arginine may function as contact residues between the BBA and streptococci during the aggregation.