Cell surface coaggregation receptor polysaccharide of oral streptococci

Abstract

BackgroundCoaggregations of viridans group streptococci with other members of the oral microbial community play an important role in dental plaque biofilm formation. These interactions generally depend on lectin-like recognition of specific host-like motifs within the hexa- and heptasaccharide repeating units of different streptococcal receptor polysaccharides (RPS). To date, seven structural types of RPS (1Gn, 2Gn, 2G, 3Gn, 3G, 4Gn, and 5Gn) have been identified from over 25 different streptococcal strains. The repeating units of different RPS types invariably contain either GalNAcβ1-3Gal (Gn) or Galβ1-3GalNAc (G) disaccharide motifs, which are receptors of Actinomyces spp. type 2 fimbriae. Streptococci that bear Gn types of RPS also coaggregate with strains of Streptococcus gordonii and S. sanguinis that bear GalNAc-binding adhesins. HighlightInsight into the genetic basis of RPS structure and function was gained from comparative characterization of gene clusters that are involved in RPS production that occurs in different streptococci by carbohydrate engineering, which involves gene swapping between strains to obtain polysaccharides with altered structural and biological properties. ConclusionProduction of genetically modified polysaccharides on bacterial cell surfaces (i.e., carbohydrate engineering) appears to be useful for a wide range of potential applications for basic research on polysaccharide structure and function as well as in the possible production of new or improved vaccines.