Streptococcus mutans extracellular DNA levels depend on the number of bacteria in a biofilm

Miah Kim,Jaegon Kim,Jaegyu Jeon

doi:10.1038/s41598-018-31275-y

Miah Kim, Jaegon Kim + Show 1 more

Open Access

https://doi.org/10.1038/s41598-018-31275-y

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Journal: Scientific Reports	Publication Date: Sep 6, 2018
Citations: 20	License type: open-access

Affiliation: Jeonbuk National University

Abstract

Streptococcus mutans is a component of oral plaque biofilm that accumulates on the surface of teeth. The biofilm consists of extracellular components including extracellular DNA (eDNA). This study was conducted to investigate the factors that may affect the eDNA levels of S. mutans in biofilms. For the study, S. mutans UA159 biofilms were formed for 52 h on hydroxyapatite (HA) discs in 0% (w/v) sucrose +0% glucose, 0.5% sucrose, 1% sucrose, 0.5% glucose, 1% glucose, or 0.5% sucrose +0.5% glucose. Acidogenicity of S. mutans in the biofilms was measured after biofilm formation (22 h) up to 52 h. eDNA was collected after 52 h biofilm formation and measured using DNA binding fluorescent dye, SYBR Green I. Biofilms cultured in 0.5% sucrose or glucose had more eDNA and colony forming units (CFUs) and less exopolysaccharides (EPSs) than the biofilms cultured in 1% sucrose or glucose at 52 h, respectively. The biofilms formed in 0% sucrose +0% glucose maintained pH around 7, while the biofilms grown in 0.5% sucrose had more acidogenicity than those grown in 1% sucrose, and the same pattern was shown in glucose. In conclusion, the results of this study show that the number of S. mutans in biofilms affects the concentrations of eDNA as well as the acidogenicity of S. mutans in the biofilms. In addition, the thickness of EPS is irrelevant to eDNA aggregation within biofilms.

Highlights

Streptococcus mutans is one of the etiological agents of dental caries, one of the most common human infectious diseases[1,2,3]
We sought to characterize the factors associated with extracellular DNA (eDNA) aggregation in biofilms, and the results of this study show that eDNA levels in biofilms are related to the number of S. mutans in the biofilms
S. mutans is an oral bacteria that generates glucosyltansferases (Gtf B, Gtf C, and Gtf D) to produce insoluble and soluble glucans, and these glucans promote the formation of biofilms[19]

Summary

Introduction

Streptococcus mutans is one of the etiological agents of dental caries, one of the most common human infectious diseases[1,2,3]. The importance of eDNA as one of the major components of biofilms was first shown in Pseudomonas aeruginosa[10]. Biofilms can act as a barrier to prevent inflow of antibiotics; the bacteria in biofilms can be resistant to antimicrobial agents up to 1,000-fold, which makes eDNA an important target to control biofilm[18]. Researchers have studied eDNA of S. mutans for more than a decade, most studies focus on the origin and role of eDNA in biofilms, and there is no study on the factors associated with the levels of eDNA within biofilms. In the present study, we use hydroxyapatite (HA) discs to form biofilms and different concentrations of sugar to investigate any factors that affect the levels of eDNA in S. mutans biofilms

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Conclusion