Metabolic activity of Streptococcus mutans biofilms and gene expression during exposure to xylitol and sucrose

Abstract

The objective of the study was to analyse Streptococcus mutans biofilms grown under different dietary conditions by using multifaceted methodological approaches to gain deeper insight into the cariogenic impact of carbohydrates. S. mutans biofilms were generated during a period of 24 h in the following media: Schaedler broth as a control medium containing endogenous glucose, Schaedler broth with an additional 5% sucrose, and Schaedler broth supplemented with 1% xylitol. The confocal laser scanning microscopy (CLSM)-based analyses of the microbial vitality, respiratory activity (5-cyano-2,3-ditolyl tetrazolium chloride, CTC) and production of extracellular polysaccharides (EPS) were performed separately in the inner, middle and outer biofilm layers. In addition to the microbiological sample testing, the glucose/sucrose consumption of the biofilm bacteria was quantified, and the expression of glucosyltransferases and other biofilm-associated genes was investigated. Xylitol exposure did not inhibit the viability of S. mutans biofilms, as monitored by the following experimental parameters: culture growth, vitality, CTC activity and EPS production. However, xylitol exposure caused a difference in gene expression compared to the control. GtfC was upregulated only in the presence of xylitol. Under xylitol exposure, gtfB was upregulated by a factor of 6, while under sucrose exposure, it was upregulated by a factor of three. Compared with glucose and xylitol, sucrose increased cell vitality in all biofilm layers. In all nutrient media, the intrinsic glucose was almost completely consumed by the cells of the S. mutans biofilm within 24 h. After 24 h of biofilm formation, the multiparametric measurements showed that xylitol in the presence of glucose caused predominantly genotypic differences but did not induce metabolic differences compared to the control. Thus, the availability of dietary carbohydrates in either a pure or combined form seems to affect the cariogenic potential of S. mutans biofilms.

Expression of adherence genes of Streptococcus mutans in the presence of Lactobacillus acidophilus and glucose

“…Our findings are similar to Shemesh et al (2006) and Decker et al (2014) who studied the effect of different carbohydrates. In addition to this, they investigated the expression of glucosyltransferases and other biofilmassociated genes and found that the combined presence of carbohydrates stimulate the upregulation of glucanand biofilm-associated genes in a different way than glucose alone.…”

Streptococcus mutans biofilm inhibition using antisense oligonucleotide to glucosyltransferases B and C

“…The latter fact suggests an inhibition of water-insoluble glucans synthesis because these polymers are essential for the biofilm development, and no glucans lead to no biofilm formation (3,16). It should be noted that, in the presence of sucrose, S. mutans adhesion to solid surfaces (e. g. glass, tooth enamel) is mainly dependent on the activity of glucosyltransferases, especially those synthesizing water-insoluble glucans (16)(17)(18). This was evidently demonstrated by Ooshima et al (16) using S. mutans GtfB/C-deficient mutant strains -their ability to adhere to the glass surface was significantly reduced in spite of the presence of sucrose within the medium.…”

Comparison of inhibitory activity of bioactive molecules on the dextransucrase from Streptococcus mutans

“…Significant persistence of S. mutans under the acidic environment encourages the proliferation of S. mutans including other acidogenic bacteria, resulting in their ability to survive at a low-pH condition. Upon changing to the low-pH condition, the initiation of the dental caries starts under the surface of teeth covered with biofilm (Chen et al 2012;Decker et al 2014). Therefore, the potential acidification of dental biofilms and later cavity formations can be decreased by eliminating the adherence of S. mutans to the surface of teeth or dental biofilms.…”

“…Owing to these features concerted with its survivability, natural bioactive substances such as sugar-alcohol, antocyanine, and specific sugars have been focused as potent antimicrobial materials. It has been implicated that extracellular water-insoluble polysaccharide from dietary sugar produced by dextransucrase (DSase) and its adhesion to dental enamel are known to the most clinically important biological abilities of S. mutans (Chen et al 2012;Decker et al 2014). However, the mechanisms under which this cariogenic pathogen can survive or proliferate under in such environmental conditions are so far largely unknown.…”