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

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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.