Anti-Biofilm Activity of a Self-Aggregating Peptide against Streptococcus mutans

Abstract

Streptococcus mutans is the primary agent of dental cavities, in large part due to its ability to adhere to teeth and create a molecular scaffold of glucan polysaccharides on the tooth surface. Disrupting the architecture of S. mutans biofilms could help undermine the establishment of biofilm communities that cause cavities and tooth decay. Here we present a synthetic peptide P1, derived from a tick antifreeze protein, which significantly reduces S. mutans biofilm formation. Incubating cells with this peptide decreased biofilm biomass by approximately 75% in both a crystal violet microplate assay and an in vitro tooth model using saliva-coated hydroxyapatite discs. Bacteria treated with peptide P1 formed irregular biofilms with disconnected aggregates of cells and exopolymeric matrix that readily detached from surfaces. Peptide P1 can bind directly to S. mutans cells but does not possess bactericidal activity. Anti-biofilm activity was correlated with peptide aggregation and β-sheet formation in solution, and alternative synthetic peptides of different lengths or charge distribution did not inhibit biofilms. This anti-biofilm peptide interferes with S. mutans biofilm formation and architecture, and may have future applications in preventing bacterial buildup on teeth.

Design and Assessment of Anti-Biofilm Peptides: Steps Toward Clinical Application

“…Other studies have shown that peptide P1 disrupts the architecture of Streptococcus mutans biofilm and can significantly decrease viable biofilm bacteria in an in vitro saliva-coated hydroxyapatite disc tooth model compared to a control peptide [15]. Although P1 can directly bind to bacterial cells, it shows no bactericidal activity.…”

“…Biofilm-specific targets are slowly becoming increasingly recognized and investigated [15][16][17][18][19]. Original studies with LL-37 [14] indicated that this peptide acted by decreasing the attachment of bacterial cells, stimulating twitching motility, and influencing 2 major quorum sensing systems (Las and Rhl).…”

“…However, these mechanisms were quite unsatisfying, since each of these processes (attachment, motility, quorum sensing) is quite distinct in other bacterial species. Study of the broad spectrum synthetic bactenecin derivatives 1018 and DJK-5 provided insights into the mode of action of anti-biofilm peptides [15]. The basis for this activity was found to be their ability to directly target the highly conserved stringent stress response through binding to and triggering the degradation of the signaling molecule ppGpp [16,17].…”

“…Although P1 can directly bind to bacterial cells, it shows no bactericidal activity. Therefore, the authors hypothesized that this peptide might impair secretion of and/or interaction between the extracellular polymers in the matrix [15]. Another study investigated eDNA, a common component of the biofilm matrix, as a potential target for two homologous fish HDPs piscidin-1 and piscidin-3, which carry C-terminal copper binding motifs [18].…”

“…For example, targeting conserved regulatory pathways provides these peptides with extremely broad-spectrum anti-biofilm activity against multidrug resistant and clinically relevant Gram-positive and Gram-negative pathogens [11]. Unlike conventional antibiotics, these compounds have been shown to interfere with secondary messenger molecules such as ppGpp [15] and can have multiple mechanisms of action, which may decrease the possibility of resistance development in future therapies. More recently there is evidence that such peptides can also target fungal biofilms [20], but the basis for this activity is currently unknown.…”