Role and related mechanisms of LiaSR two-component system in acid tolerance and biofilm formation of Streptococcus mutans
10.3760/cma.j.cn112144-20230902-00130
- VernacularTitle:LiaSR双组分信号转导系统调控变异链球菌耐酸和生物膜形成能力的机制研究
- Author:
Shan HUANG
1
;
Jingyun DU
;
Yijun LI
;
Minjing WU
;
Shuai CHEN
;
Shan JIANG
;
Xiaojing HUANG
Author Information
1. 福建医科大学口腔医学院·附属口腔医院牙体牙髓科 福建省口腔疾病研究重点实验室 福建省口腔生物材料工程技术研究中心 福建省高校口腔医学重点实验室 福建医科大学口腔医学研究院 福建医科大学口腔组织工程研究中心，福州 350002
- Keywords:
Dental caries;
Streptococcus mutans;
Biofilms;
LiaSR two-component system;
Acid tolerance
- From:
Chinese Journal of Stomatology
2024;59(1):54-63
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To investigate the role and related mechanisms of the LiaSR two-component system in acid tolerance and biofilm formation abilities of Streptococcus mutans (Sm) 593. Methods:The growth curves of various Sm strains in pH=5.5 brian heart infusion (BHI) medium were analyzed. And colony forming unit (CFU) was also performed to evaluate the acid tolerance of Sm. Laurdan probe, H +-K +adenosine triphosphate (ATP)ase activity analysis kit, proton permeability assay and real-time fluorescence quantitative PCR (RT-qPCR) were conducted to detect the acid tolerant mechanisms of LiaSR two-component system in Sm. Crystal violet staining, CFU, SYTOX probe and anthrone-sulfuric method were used to analyze the properties and structures of the Sm biofilms. RT-qPCR was conducted to detect the expression levels of underlying regulated genes. Results:The growth of mutants in acidic BHI were inhibited ( P<0.05). The acid tolerance of mutants significantly decreased compared to the wild-type strain ( P<0.05). In mutants, the activity of H +-ATPase (917.06±59.53 and 469.53±47.65) were elevated by 7.22-folds and 3.70-folds compared to the wild-type strain (127.00±50.71) ( P<0.001, P<0.001) and the encoded gene atpD (3.39±0.21 and 1.94±0.17) were also elevated by 3.39-folds and 1.94-folds compared to the wild-type strain (1.00±0.15) ( P<0.001, P=0.001). The Laurdan generalized polarization of mutants (0.18±0.04 and 0.18±0.05) increased significantly compared to the wild-type strain (0.08±0.05) ( P=0.006, P=0.003) and the expression levels of fabM gene were decreased in mutants (0.52±0.11 and 0.57±0.05) by 1/2 ( P=0.014, P=0.022). In liaR deletion mutant, the reduced terminal pH (4.76±0.01) can also be observed ( P<0.001). The total amount of the biofilms of three Sm didn't show significant differences ( P>0.05). But the number of viable bacteria of mutants′ biofilms were decreased [Sm 593: (12.00±2.80)×10 7 CFU/ml; Sm ΔliaS: (2.95±1.13)×10 7 CFU/ml; Sm ΔliaR: (7.25±1.60)×10 7 CFU/ml] ( P=0.001, P=0.024). The extracellular DNA were increased by 18.00-folds and 6.50-folds in mutants′ biofilms (128.73±15.65 and 46.38±5.52) compared to the wild-type strain (7.16±3.62) ( P<0.001, P=0.003). Water-soluble exopolysaccharides could be found up-regulated in liaS deletion mutant [(138.73±10.12) μg/ml] ( P=0.003) along with the expression level of gtfC gene (1.65±0.39) ( P=0.014). The expression level of gtfD were elevated by 47.43-folds and 16.90-folds in mutants ( P<0.001, P=0.010). Conclusions:The LiaSR two-component system can promote the expression of fabM gene and increase the fluidity of Sm which contributes to acid tolerance. The LiaR can also decrease the proton permeability and restrict the entrance of H +. The LiaSR two-component system can negatively regulate the production of the extracellular matrix in Sm biofilm.
