Lauryl Gallate Activity and Streptococcus mutans: Its Effects on Biofilm Formation, Acidogenicity and Gene Expression.

Vika Gabe,Mizied Falah,Maksim Bratchikov,Tomas Kacergius,Anwar Rayan,Mouhammad Zeidan

doi:10.3390/molecules25163685

Abstract

Streptococcus mutans bacterium is implicated in the pathogenesis of dental caries due to the production of biofilm and organic acids from dietary sucrose. Despite the availability of various means of prophylaxis, caries still has a high worldwide prevalence. Therefore, it is important to find new pharmaceuticals to inhibit S. mutans biofilm formation and acidogenicity. The aim of the current study was to evaluate the activity of lauryl gallate (dodecyl gallate) against S. mutans acidogenicity, the expression of biofilm-associated genes, and biofilm development on solid surfaces (polystyrene, glass). The biofilm quantities produced by S. mutans bacteria were assessed using colorimetric and optical profilometry techniques. Acidogenicity was evaluated by measuring the pH of the biofilm growth medium with microelectrode. Assessment of the expression of gene coding for glucan-binding protein B (gbpB), glucosyltranferases B, -C, -D (gtfB, -C, -D), and the F-ATPase β subunit of F1 protein (atpD) was carried out using a quantitative reverse transcription-polymerase chain reaction (RT-qPCR). The results demonstrate the capacity of lauryl gallate to significantly inhibit S. mutans acidogenicity and biofilm development on solid surfaces, in a dose-dependent manner, compared to untreated bacteria (p < 0.05). The highest activity of lauryl gallate occurred at a concentration of 98.98 µM, at which it suppressed biofilm formation by 100% and lowered pH levels by 98%. The effect of lauryl gallate treatment on gene expression changes, as demonstrated by our RT-qPCR data, was limited to the gtfD gene only, was a significant (48%) decrease in gene expression, obtained for the biofilm-producing bacteria, while a 300% increase in fold change for the same gene occurred in the planktonic cells. It is important to note that in previous studies we showed a broader effect of related derivatives. However, a similar magnitude of difference in effects between biofilm and planktonic cells for the atpD gene was obtained after treatment with octyl gallate and reverse magnitude for the same gene after treatment with ethyl gallate. Therefore, to ascertain the possible direct or indirect effects of lauryl gallate, as well as octyl gallate and ethyl gallate, more research is needed to examine the effects on the amount of enzymes and on the enzymatic activity of the products of the affected genes that are involved in the production and maintenance of biofilm by S. mutans.

Highlights

Streptococcus mutans is an important bacterial species of human oral microbiota that predominantly colonizes the hard tissue surfaces of teeth, causing dental caries through sucrose-dependent adhesion and consequent biofilm formation [1,2]
Other natural derivatives of alkyl gallates that have been shown to significantly suppress S. mutans biofilm formation are methyl gallate (C1-MG) and ethyl gallate (C2-EG) [27,28], and we have demonstrated that an octyl gallate derivative (C8-OG) significantly diminished biofilm formation and suppressed the associated genes expressed in S. mutans [29]
This study focused on the effects of lauryl gallate (C12-LG) against S. mutans biofilm formation on solid surfaces and on its acidogenicity and expression of biofilm-associated genes

Summary

Introduction

Streptococcus mutans is an important bacterial species of human oral microbiota that predominantly colonizes the hard tissue surfaces of teeth, causing dental caries through sucrose-dependent adhesion and consequent biofilm formation [1,2]. This mechanism involves the utilization of dietary sucrose by the S. mutans glucosyltransferases, GtfB, -C, and -D, to produce water-insoluble, partly soluble, and soluble glucan polymers, respectively [3,4]. Sucrose is further fermented by S. mutans bacteria to produce lactic acid, thereby lowering the pH to values below 5.0 within the biofilm [6,7] This results in rapid acidification of the dental biofilm, which is subsequently sustained by the proton-translocating F-type ATPase of. The activity of F-type ATPase maintains steady acidogenicity in the biofilm, which in turn causes the dissolution of tooth enamel with the development of carious lesions (i.e., dental caries) [6,9]

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