Abstract
The enzyme alanine racemase (Alr) has been a new target for the development of antibacterial drugs based on the involvement of D-Ala in bacterial cell wall biosynthesis. Our previous study noted that Alr is essential for the growth and interspecies competitiveness of S. mutans, the major causative organism of dental caries. However, physiological activity and cariogenicity of S. mutans affected by Alr remains unknown. The current study examined the biofilm biomass, biofilm structure, extracellular polysaccharide (EPS) synthesis, glucosyltransferase (gtf) gene expression, acid production and acid tolerance in the alr-mutant strain. We found that biofilm formation, biofilm structure, and EPS synthesis was in a D-Ala dose-dependent manner. Biofilm structure was loose in alr-mutant group and the ratio of EPS/bacteria was also elevated. Additionally, the expression levels of multiple gtfs were up-regulated, and acid tolerance was decreased. We also established in vivo models of dental caries and found that the incidence and severity of the caries were decreased in the alr-mutant group in comparison to the parental S. mutans group. Our in vivo and in vitro experiments demonstrate that Alr is essential for the cariogenicity of S. mutans and that Alr might be a potential target for the prevention and treatment of caries.
Highlights
Alanine racemase (Alr) is a bacterial enzyme that catalyses the conversion of L-alanine to D-alanine (D-Ala)[1]
We have studied the growth of WT S. mutans affected by exogenous D-Ala, and the result showed that exogenous D-Ala did not obviously affect the growth of S. mutans
To explore whether alanine racemase (Alr) can represent an effective drug target to modulate the cariogenicity of oral biofilm and benefit the management of dental caries, we firstly determined that Alr is essential for the growth and interspecies competitiveness of S. mutans[17]
Summary
Alanine racemase (Alr) is a bacterial enzyme that catalyses the conversion of L-alanine to D-alanine (D-Ala)[1]. Considering the essential role of D-alanine for the bacterial cell wall, the alr gene is a potential antibacterial target for S. mutans. The depletion of D-Ala in the growth medium led to cell wall perforation and cell lysis in the alr-mutant strain[17]. Another previous study demonstrated the important role of D-Ala metabolism for the growth of S. mutans[18]. Given the importance of alr to the growth of S. mutans, the aim of this study was to explore the role of Alr on the physiological activity, including biofilm formation, extracellular polysaccharide (EPS) synthesis, glucosyltransferases (gtfs) gene expression, acids production and tolerance, and cariogenicity of S. mutans
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
