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Infect. Immun. doi:10.1128/IAI.01544-06
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The glycan moieties and the N-terminal polypeptide backbone of a fimbriae-associated adhesin, Fap1, play distinct roles in the biofilm development of Streptococcus parasanguis

Departments of Pediatric Dentistry and Microbiology, University of Alabama at Birmingham, Schools of Dentistry and Medicine, Birmingham, AL 35294, Department of Microbiology & Molecular Genetics, College of Medicine and College of Agriculture and Life Sciences, University of Vermont, Burlington, Vermont 05405, U.S.A

^* To whom correspondence should be addressed. Email: hwu{at}uab.edu.

	Abstract

Fap1, a fimbriae-associated glycoprotein, is essential for biofilm formation of Streptococcus parasanguis and mediates bacterial attachment to saliva-coated hydroxylapatite (SHA), an in vitro tooth model (13, 38, 40). Fap1 belongs to a growing family of high molecular weigh serine-rich proteins found in streptococcal and staphylococcal species and possesses two serine-rich repeat regions. The glycan moiety of Fap1 appears to be O-linked within the repeat regions (29). In this study, we identified a gene cluster immediately upstream of fap1 which encodes three putative glycosyltransferases and one nucleotide-sugar synthetase-like protein. Inactivation of one glycosyltransferase gene galT2 abolished the expression of two glycan-epitopes; however it did not alter bacterial ability to adhere to both SHA and saliva-conditioned biofilm surfaces. By contrast, the biofilms formed by the galT2 mutant were shallow and had a 70% decrease in biomass accumulation, suggesting these glycan moieties mediated by GalT2 are not required for the initial adhesion but important for biofilm formation. A recombinant N-terminal Fap1 polypeptide was shown to interact with a 53 kDa salivary protein, block and displace bacterial attachment, further demonstrating the role of the Fap1 polypeptide in the bacterial adhesion. Taken together, these results suggested that Fap1 glycosylation plays an important role in bacterial biofilm formation while the non-glycosylated Fap1 peptide mediates bacterial initial attachment during the process of biofilm formation.

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• Bu, S., Li, Y., Zhou, M., Azadin, P., Zeng, M., Fives-Taylor, P., Wu, H. (2008). Interaction between Two Putative Glycosyltransferases Is Required for Glycosylation of a Serine-Rich Streptococcal Adhesin. J. Bacteriol. 190: 1256-1266 [Abstract] [Full Text]