Poster Sessions

MB -3

Jinghua Yang

J. Yang, Y. Yoshida, M. Ritchey, C. A. Bush, J. O. Cisar

Comparative Molecular Characterization of Ribitol-5-Phosphate-Containing Coaggregation Receptor Polysaccharides from Strains of Streptococcus oralis

Coaggregation receptor polysaccharides (RPS) of Streptococcus oralis C104 and SK144 mediate lectin-like recognition of these bacteria by other members of the dental plaque biofilm community. The structure of strain C104 RPS, which is [-6-beta-Galf1-6-beta-GalNAc1-3-alpha-Gal1-1ribitol-5-phosphate-6-beta-Galf1-3-beta-Gal1-]n, is identical to that of strain SK144 RPS except for the presence of an alpha 1-3 linkage between Gal and ribitol-5-phosphate of the latter molecule. In the present investigation, the RPS gene cluster of each S.oralis strain was identified. Cell surface RPS production was abolished by replacing the gene for the first transferase of strain C104 with a non polar ermAM. RPS production was restored in the resulting mutant by plasmid-based expression of either wcjG, the corresponding gene of S.pneumoniae for serotype 10A capsular polysaccharide (CPS) biosynthesis or wbaP of Salmonella enterica. Thus, WcjG appears to involve the transfer of galactose-1-phosphate to a lipid carrier. In further studies, the structure of strain C104 RPS was converted to that of strain SK144 by replacing the gene (wefM) of strain C104 with the corresponding gene (wefN) of strain SK144. The findings define the molecular basis of the structural difference between S.oralis C104 and SK144 RPS and suggest a close relationship between these polysaccharides and serogroup 10 S.pneumoniae CPS.