Céline Marie Lévesque

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The induction of genetic competence is a strategy used by bacteria to increase their genetic repertoire under stressful environmental conditions. Recently, Streptococcus pneumoniae has been shown to co-ordinate the uptake of transforming DNA with fratricide via increased expression of the peptide pheromone responsible for competence induction. Here, we(More)
AIM To assess potential function of each two-component signal transduction system in the expression of Streptococcus mutans virulence properties. METHODS AND RESULTS For each two-component system (TCS), the histidine kinase-encoding gene was inactivated by a polymerase chain reaction (PCR)-based deletion strategy and the effects of gene disruption on the(More)
Within a given microbial population, a small subpopulation known as dormant persister cells exists. This persistence property ensures the survival of the population as a whole in the presence of lethal factors. Although persisters are highly important in antibiotic therapy, the mechanism for persistence is still not thoroughly understood. We show here that(More)
Streptococcal competence-stimulating peptides (CSPs) were once thought to passively communicate population density in a process known classically as quorum sensing. However, recent evidence has shown that these peptides may also be inducible 'alarmones,' capable of conveying sophisticated messages in a population including the induction of altruistic(More)
Streptococcus mutans, a normal inhabitant of dental plaque, is considered a primary etiological agent of dental caries. Its main virulence factors are acidogenicity and aciduricity, the abilities to produce acid and to survive and grow at low pH, respectively. Metabolic processes are finely regulated following acid exposure in S. mutans. Proteome analysis(More)
The oral biofilm organism Streptococcus mutans must face numerous environmental stresses to survive in its natural habitat. Under specific stresses, S. mutans expresses the competence-stimulating peptide (CSP) pheromone known to induce autolysis and facilitate the uptake and incorporation of exogenous DNA, a process called DNA transformation. We have(More)
AIMS To identify the genes regulated by RR11, the regulator of the Streptococcus mutans HK/RR11 two-component system. METHODS AND RESULTS The S. mutans RR11-encoding gene was inactivated, and the effects of gene disruption on the cell's ability to form biofilms under stresses and acquire extracellular DNA were tested. Biofilm was reduced in cells lacking(More)
Maintaining cell envelope integrity is critical for bacterial survival, including bacteria living in a complex and dynamic environment such as the human oral cavity. Streptococcus mutans, a major etiological agent of dental caries, uses two-component signal transduction systems (TCSTSs) to monitor and respond to various environmental stimuli. Previous(More)
The signal recognition particle (SRP)-translocation pathway is conserved in all three domains of life and delivers membrane and secretory proteins to the cytoplasmic membrane or endoplasmic reticulum. We determined the requirement in the cariogenic oral pathogen Streptocococcus mutans of the three universally conserved elements of the SRP pathway:(More)
Streptococcus mutans is considered one of the main causative agents of human dental caries. Cell-cell communication through two-component signal transduction systems (TCSTS) plays an important role in the pathogenesis of S. mutans. One of the S. mutans TCSTS, ComDE, controls both competence development and biofilm formation. In this study, we showed that(More)