Influence of the CovR regulator in Streptococcus mutans response to contact with saliva and blood

Author(s)

Natália Leal Vizoto

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2011-01-07

Examining board members

Renata de Oliveira Mattos Graner; Silvana Cai; Flávia Sammartino Mariano Rodrigues

• Advisor: Renata de Oliveira Mattos Graner

Abstract

Streptococcus mutans is the main pathogen of dental caries in humans, because it can accumulate in the biofilm in the presence of sucrose and produce and tolerate high concentrations of acids, which cause demineralization of teeth. Moreover, S. mutans is involved in the etiology of bacterial endocarditis, a disease whose evolution involves the formation of biofilms on damaged heart valves. S. mutans expresses several surface proteins involved in bacterial adhesion and accumulation in biofilms. These include the glucosiltransferases (gtfB, gtfC and gtfD), which synthesize extracellular glucans from sucrose, and glucan binding proteins (encoded by gbpA/B/C/D). The genes gtfB/C/D, and gbpB/C are directly controlled by the regulatory protein CovR. In several pathogenic species of Streptococcus, such as S. pyogenes and S. agalactiae, CovR is the transcriptional regulator that compose the two-component system CovRS (Cov for control of virulence), which regulates several virulence genes. In S. mutans, CovR was identified as an orphan regulator, because the gene encoding its cognate membrane receptor was not identified at the same locus of covR. In S. mutans, CovR regulates several genes involved in biofilm formation (gtfB/C, and gbpB/C), in biosynthesis of the cell envelope and in stress responses. The stimuli which activate CovR in S. mutans are not yet known. This project aims to characterize the participation of CovR in S. mutans response to contact with saliva and blood. To this purpose, a knock-out mutant of covR was compared with parent strain regarding growth and/or survival in human saliva and blood. The effect of exposure to saliva in the expression of genes directly by covR was also analyzed (AU)

• FAPESP's process: 09/02803-8 - Influence of the CovR regulator in Streptococcus mutans response to contact with saliva and blood
• Grantee: Natália Leal Vizoto
• Support Opportunities: Scholarships in Brazil - Master