A Strain of Inhibits Biofilm Formation of Caries Pathogens via Abundant Hydrogen Peroxide Production.

Commensal oral streptococci that colonize supragingival biofilms deploy mechanisms to combat competitors within their niche. Here, we determined that more effectively inhibited biofilm formation of within a seven species panel. This phenotype was common amongst all assayed isolates of , but was specific to a single strain of , ATCC 49456.

Human saliva modifies growth, biofilm architecture, and competitive behaviors of oral streptococci.

Unlabelled: The bacteria within supragingival biofilms participate in complex exchanges with other microbes inhabiting the same niche. One example is the mutans group streptococci (s), implicated in the development of tooth decay, and other health-associated commensal streptococci species. Previously, our group transcriptomically characterized intermicrobial interactions between and several species of oral bacteria.

Human Saliva Modifies Growth, Biofilm Architecture and Competitive Behaviors of Oral Streptococci.

The bacteria within supragingival biofilms participate in complex exchanges with other microbes inhabiting the same niche. One example are the mutans group streptococci (s), implicated in the development of tooth decay, and other health-associated commensal streptococci species. Previously, our group transcriptomically characterized intermicrobial interactions between and several species of oral bacteria.

Complete Genome Sequence of Streptococcus oralis 34.

Streptococcus oralis is an early colonizer and one of the most abundant species found in the human oral cavity. We report the complete genome sequence of S. oralis 34 (1,920,884 bp; GC content, 41.

A single system detects and protects the beneficial oral bacterium Streptococcus sp. A12 from a spectrum of antimicrobial peptides.

The commensal bacterium Streptococcus sp. A12 has multiple properties that may promote the stability of health-associated oral biofilms, including overt antagonism of the dental caries pathogen Streptococcus mutans. A LanFEG-type ABC transporter, PcfFEG, confers tolerance to the lantibiotic nisin and enhances the ability of A12 to compete against S.

Spatial Correlations and Distribution of Competence Gene Expression in Biofilms of .

is an important pathogen in the human oral biofilm. It expresses virulent behaviors that are linked to its genetic competence regulon, which is controlled by . Expression of is modulated by two diffusible signaling peptides, denoted CSP and XIP, and by other environmental cues such as pH and oxidative stress.

Direct interactions with commensal streptococci modify intercellular communication behaviors of Streptococcus mutans.

The formation of dental caries is a complex process that ultimately leads to damage of the tooth enamel from acids produced by microbes in attached biofilms. The bacterial interactions occurring within these biofilms between cariogenic bacteria, such as the mutans streptococci, and health-associated commensal streptococci, are thought to be critical determinants of health and disease. To better understand these interactions, a Streptococcus mutans reporter strain that actively monitors cell-cell communication via peptide signaling was cocultured with different commensal streptococci.

Expanding the Vocabulary of Peptide Signals in .

Streptococci, including the dental pathogen , undergo cell-to-cell signaling that is mediated by small peptides to control critical physiological functions such as adaptation to the environment, control of subpopulation behaviors and regulation of virulence factors. One such model pathway is the regulation of genetic competence, controlled by the ComRS signaling system and the peptide XIP. However, recent research in the characterization of this pathway has uncovered novel operons and peptides that are intertwined into its regulation.

Spontaneously Arising Streptococcus mutans Variants with Reduced Susceptibility to Chlorhexidine Display Genetic Defects and Diminished Fitness.

Chlorhexidine (CHX) has been used to control dental caries caused by acid-tolerant bacteria such as since the 1970s. Repeat CHX exposure for other bacterial species results in the development of variants with reduced susceptibility that also become more resistant to other antimicrobials. It has not been tested if such variants arise when streptococci are exposed to CHX.

Intracellular Signaling by the System in Genetic Competence.

Entry into genetic competence in streptococci is controlled by ComX, an alternative sigma factor for genes that enable the import of exogenous DNA. In , the immediate activator of is the ComRS quorum system. ComS is the precursor of XIP, a seven-residue peptide that is imported into the cell and interacts with the cytosolic receptor ComR to form a transcriptional activator for both and Although intercellular quorum signaling by ComRS has been demonstrated, observations of bimodal expression of suggest that may also function as an intracellular feedback loop, activating without export or detection of extracellular XIP.

Competence inhibition by the XrpA peptide encoded within the comX gene of Streptococcus mutans.

Streptococcus mutans displays complex regulation of natural genetic competence. Competence development in S. mutans is controlled by a peptide derived from ComS (XIP); which along with the cytosolic regulator ComR controls the expression of the alternative sigma factor comX, the master regulator of competence development.

Intercellular Communication via the -Inducing Peptide (XIP) of Streptococcus mutans.

Gram-positive bacteria utilize exported peptides to coordinate genetic and physiological processes required for biofilm formation, stress responses, and ecological competitiveness. One example is activation of natural genetic competence by ComR and the -nducing eptide (XIP) in Although the competence pathway can be activated by the addition of synthetic XIP in defined medium, the hypothesis that XIP is able to function as an intercellular signaling molecule has not been rigorously tested. Coculture model systems were developed that included a "sender" strain that overexpressed the XIP precursor (ComS) and a "responder" strain harboring a green fluorescent protein (GFP) reporter fused to a ComR-activated gene () promoter.

An Essential Role for (p)ppGpp in the Integration of Stress Tolerance, Peptide Signaling, and Competence Development in Streptococcus mutans.

The microbes that inhabit the human oral cavity are subjected to constant fluctuations in their environment. To overcome these challenges and gain a competitive advantage, oral streptococci employ numerous adaptive strategies, many of which appear to be intertwined with the development of genetic competence. Here, we demonstrate that the regulatory circuits that control development of competence in Streptococcus mutans, a primary etiological agent of human dental caries, are integrated with key stress tolerance pathways by the molecular alarmone (p)ppGpp.

A unique open reading frame within the comX gene of Streptococcus mutans regulates genetic competence and oxidative stress tolerance.

Streptococcus mutans displays complex regulation of genetic competence, with ComX controlling late competence gene transcription. The rcrRPQ operon has been shown to link oxidative stress tolerance, (p)ppGpp metabolism and competence in S. mutans.

Discovery of novel peptides regulating competence development in Streptococcus mutans.

A MarR-like transcriptional repressor (RcrR) and two predicted ABC efflux pumps (RcrPQ) encoded by a single operon were recently shown to be dominant regulators of stress tolerance and development of genetic competence in the oral pathogen Streptococcus mutans. Here, we focused on polar (ΔrcrR-P) and nonpolar (ΔrcrR-NP) rcrR mutants, which are hyper- and nontransformable, respectively, to dissect the mechanisms by which these mutations impact competence. We discovered two open reading frames (ORFs) in the 3' end of the rcrQ gene that encode peptides of 27 and 42 amino acids (aa) which are also dramatically upregulated in the ΔrcrR-NP strain.

Growth phase and pH influence peptide signaling for competence development in Streptococcus mutans.

The development of competence by the dental caries pathogen Streptococcus mutans is mediated primarily through the alternative sigma factor ComX (SigX), which is under the control of multiple regulatory systems and activates the expression of genes involved in DNA uptake and recombination. Here we report that the induction of competence and competence gene expression by XIP (sigX-inducing peptide) and CSP (competence-stimulating peptide) is dependent on the growth phase and that environmental pH has a potent effect on the responses to XIP. A dramatic decline in comX and comS expression was observed in mid- and late-exponential-phase cells.