Abstract
The combination of sucrose and starch in the presence of surface-adsorbed salivary α-amylase and bacterial glucosyltransferases increase the formation of a structurally and metabolically distinctive biofilm by Streptococcus mutans. This host-pathogen-diet interaction may modulate the formation of pathogenic biofilms related to dental caries disease. We conducted a comprehensive study to further investigate the influence of the dietary carbohydrates on S. mutans-transcriptome at distinct stages of biofilm development using whole genomic profiling with a new computational tool (MDV) for data mining. S. mutans UA159 biofilms were formed on amylase-active saliva coated hydroxyapatite discs in the presence of various concentrations of sucrose alone (ranging from 0.25 to 5% w/v) or in combination with starch (0.5 to 1% w/v). Overall, the presence of sucrose and starch (suc+st) influenced the dynamics of S. mutans transcriptome (vs. sucrose alone), which may be associated with gradual digestion of starch by surface-adsorbed amylase. At 21 h of biofilm formation, most of the differentially expressed genes were related to sugar metabolism, such as upregulation of genes involved in maltose/maltotriose uptake and glycogen synthesis. In addition, the groEL/groES chaperones were induced in the suc+st-biofilm, indicating that presence of starch hydrolysates may cause environmental stress. In contrast, at 30 h of biofilm development, multiple genes associated with sugar uptake/transport (e.g. maltose), two-component systems, fermentation/glycolysis and iron transport were differentially expressed in suc+st-biofilms (vs. sucrose-biofilms). Interestingly, lytT (bacteria autolysis) was upregulated, which was correlated with presence of extracellular DNA in the matrix of suc+st-biofilms. Specific genes related to carbohydrate uptake and glycogen metabolism were detected in suc+st-biofilms in more than one time point, indicating an association between presence of starch hydrolysates and intracellular polysaccharide storage. Our data show complex remodeling of S. mutans-transcriptome in response to changing environmental conditions in situ, which could modulate the dynamics of biofilm development and pathogenicity.
Highlights
Dental caries continues to be the single most common biofilmdependent oral infectious disease worldwide [1]
S. mutans has multiple sugar transport systems involved in the uptake of starch hydrolysates [11,12,13], which can be further metabolized into acids [14]
We initially investigated the effects of different concentrations of sucrose alone or in combination with starch on extracellular polysaccharide (EPS) matrix formation and biofilm accumulation on the saliva-coated hydroxyapatite surface (Appendix S1)
Summary
Dental caries continues to be the single most common biofilmdependent oral infectious disease worldwide [1]. Streptococcus mutans, a member of the oral microbial community, plays a key role in modulating the transition from non-pathogenic form to highly cariogenic biofilms [3], additional organisms may be associated with this ubiquitous disease (as reviewed in [4]) This bacterium is able to thrive and compete in the complex biofilm microbiome, and contribute to the pathogenesis of dental caries because it: (i) effectively utilizes dietary sucrose to rapidly synthesize exopolysaccharides (EPS) through glucosyltransferases and a fructosyltransferase that adsorb to surfaces, (ii) adheres tenaciously to glucan-coated surfaces, and (iii) is highly acidogenic and aciduric [2,5]. We developed a new software to analyze the microarray data, focusing on how specific transcriptome changes may be associated with enhanced biofilms accumulation, survival and virulence of this pathogen
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
