Abstract
Streptococcus mutans (S. mutans) is generally regarded as a major contributor to dental caries because of its ability to synthesize extracellular polysaccharides (EPS) that aid in the formation of plaque biofilm. The VicRKX system of S. mutans plays an important role in biofilm formation. The aim of this study was to investigate the effects of vicK gene on specific characteristics of EPS in S. mutans biofilm. We constructed single-species biofilms formed by different mutants of vicK gene. Production and distribution of EPS were detected through atomic force microscopy, scanning electron microscopy and confocal laser scanning microscopy. Microcosmic structures of EPS were analyzed by gel permeation chromatography and gas chromatography-mass spectrometry. Cariogenicity of the vicK mutant was assessed in a specific pathogen-free rat model. Transcriptional levels of cariogenicity-associated genes were confirmed by quantitative real-time polymerase chain reaction. The results showed that deletion of vicK gene suppressed biofilm formation as well as EPS production, and EPS were synthesized mostly around the cells. Molecular weight and monosaccharide components underwent evident alterations. Biofilms formed in vivo were sparse and contributed a decreased degree of caries. Moreover, expressional levels of genes related to EPS synthesis were down-regulated, except for gtfB. Our report demonstrates that vicK gene enhances biofilm formation and subsequent caries development. And this may due to its regulations on EPS metabolism, like synthesis or microcosmic features of EPS. This study suggests that vicK gene and EPS can be considered as promising targets to modulate dental caries.
Highlights
Dental caries is a chronic infectious disease occurring on mineralized tooth tissue, which is considered one of the most common health problems globally in 2015 posing considerable economic, social, and health-related burden.[1,2,3] Streptococcus mutans (S. mutans) is important in caries development because of its ability to synthesize extracellular polysaccharides (EPS) matrix.[4]
The results showed that deletion of vicK gene suppressed biofilm formation as well as EPS production, and EPS were synthesized mostly around the cells
This study suggests that vicK gene and EPS can be considered as promising targets to modulate dental caries
Summary
Dental caries is a chronic infectious disease occurring on mineralized tooth tissue, which is considered one of the most common health problems globally in 2015 posing considerable economic, social, and health-related burden.[1,2,3] Streptococcus mutans (S. mutans) is important in caries development because of its ability to synthesize extracellular polysaccharides (EPS) matrix.[4]. It can function as a sensor for environmental signals and provide a long-term dynamic protection for microbial communities.[6,8] Nowadays, with the thriving development of targeted therapies, regulations on EPS metabolism and biofilm formation have gained considerable attention.[9,10] Nanoparticles have been used to disrupt biofilm and a small molecule which can selectively target S. mutans biofilms has been reported to effectively reduce dental caries in vivo without affecting the overall oral microbiota.[11,12] Researchers have found that the production, distribution as well as microcosmic characteristics of EPS all take a considerable part in the pathogenicity of polymicrobial biofilm.[13,14] So, an understanding of specific characteristics of EPS derived from S. mutans biofilm will provide more solid evidences for caries prevention, which have not been elucidated yet
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