title: Glucan-binding proteins are essential for shaping Streptococcus mutans biofilm architecture.
abstract: Glucan plays a central role in sucrose-dependent biofilm formation by the dental pathogen Streptococcus mutans. This organism synthesizes several proteins capable of binding glucan. These are divided into the glucosyltransferases that catalyze the synthesis of glucan and the nonglucosyltransferase glucan-binding proteins (Gbps). The biological significance of the Gbps has not been thoroughly defined, but studies suggest that these proteins influence virulence and play a role in maintaining biofilm architecture by linking bacteria and extracellular molecules of glucan. We engineered a panel of Gbp mutants, targeting GbpA, GbpC, and GbpD, in which each gene encoding a Gbp was deleted individually and in combination. These strains were then analyzed by confocal microscopy and the biofilm properties were quantified by the biofilm quantification software comstat. All biofilms produced by mutant strains lost significant depth, but the basis for the reduction in height depended on which particular Gbp was missing. The loss of the cell-bound GbpC appeared dominant as might be expected based on losing the principal receptor for glucan. The loss of an extracellular Gbp, either GbpA or GbpD, also profoundly changed the biofilm architecture, each in a unique manner.
authors.affiliation: Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Lynch
authors.forename: Tracey L
authors.initials: TL
authors.lastname: Fountain
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Mazurkiewicz
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Banas
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology; D018441:Biofilms / Q000254:growth & development*; D002352:Carrier Proteins / Q000502:physiology*; D017353:Gene Deletion; D005798:Genes, Bacterial / Q000235:genetics; D037102:Lectins / Q000502:physiology*; D013295:Streptococcus mutans / Q000472:pathogenicity / Q000502:physiology*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D037102:Lectins; C037937:glucan-binding proteins