OBJECTIVES: This study aims to investigate the impact of glutathione S-transferase (GST) on the environmental adaptability of Streptococcus mutans (S. mutans). METHODS: A GST knockout strain ΔgsT was constructed. Transcriptomic sequencing was performed to analyze the gene expression differences between the wild-type S. mutans UA159 and its GST knockout strain ΔgsT. Comprehensive functional assessments, including acid tolerance assays, hydrogen peroxide challenge assays, nutrient limitation growth assays, and fluorescence in situ hybridization, were conducted to evaluate the acid tolerance, antioxidant stress resistance, growth kinetics, and interspecies competitive ability of ΔgsT within plaque biofilms. RESULTS: Compared with the wild-type S. mutans, 198 genes in ΔgsT were significantly differentially expressed and enriched in pathways related to metabolism, stress response, and energy homeostasis. The survival rate of ΔgsT in acid tolerance assays was markedly reduced (P<0.01). After 15 min of hydrogen peroxide challenge, the survival rate of ΔgsT decreased to 38.12% (wild type, 71.75%). Under nutrient-limiting conditions, ΔgsT exhibited a significantly lower final OD₆₀₀ value than the wild-type strain (P<0.05). In the biofilm competition assays, the proportion of S. mutans ΔgsT in the mixed biofilm (8.50%) was significantly lower than that of the wild type (16.89%) (P<0.05). CONCLUSIONS GST enhances the acid resistance, oxidative stress tolerance, and nutrient adaptation of S. mutans by regulating metabolism-related and stress response-related genes.
Streptococcus mutans/enzymology* ; Biofilms ; Glutathione Transferase/physiology* ; Adaptation, Physiological ; Hydrogen Peroxide/pharmacology* ; Gene Expression Regulation, Bacterial ; Oxidative Stress ; Metabolic Reprogramming

Due to the wide application of silver-containing dressings and silver-coated medical devices in clinical treatment; the extensive use of antibacterial agents and heavy metal agents in feed factories, Escherichia coli has formed the tolerance to silver ions. To systematically understand the known silver ion resistance mechanisms of E. coli, this article reviews the complex regulatory network and various physiological mechanisms of silver ion tolerance in E. coli, including the regulation of outer membrane porins, energy metabolism modulation, the role of efflux systems, motility regulation, and silver ion reduction. E. coli reduces the influx of silver ions by missing or mutating outer membrane porins such as OmpR, OmpC, and OmpF. It adapts to high concentrations of silver ions by altering the expression of ArcA/B and enhances the efflux capacity of silver ions under high-concentration silver stress via the endogenous Cus system and exogenous Sil system. Furthermore, the motility of bacteria is related to silver tolerance. E. coli has the ability to reduce silver ions, thereby alleviating the oxidative stress induced by silver ions. These findings provide a new perspective for understanding the formation and spread of bacterial tolerance and provide directions for the development of next-generation silver-based antimicrobials and therapies.
Escherichia coli/genetics* ; Silver/pharmacology* ; Drug Resistance, Bacterial ; Anti-Bacterial Agents/pharmacology* ; Porins/metabolism*

Objective:To investigate the metabolic disorders in placental tissues of dexamethasone induced cleft palate mode.Methods:Twelve pregnant rabbits were randomly divided into dexamethasone group (experimental group, 8) and saline control group (4), and a certain amount of dexamethasone and saline were administered intramuscularly to the experimental and control groups respectively from embryonic days (ED) 13 to 16, and placental tissue samples were collected on day 21 of gestation. The corresponding profiles of the embryonic placental tissue samples were obtained by liquid chromatography-triple tandem quadrupole(LC-MS), and the metabolites of the embryonic placental tissues were characterized by principal component analysis among the dexamethasone-treated group with cleft palate (D-CP group), the dexamethasone-treated group without cleft palate (D-NCP group) and the control group.Results:There were significant metabolic differences among the D-CP group, D-NCP group and control group, with a total of 133 differential metabolites (VIP>1, P<0.05) involving in important metabolic pathways including vitamin B6 metabolism, lysine metabolism, arginine anabolic metabolism, and galactose metabolism. The four metabolites, vitamin B6, galactose, lysine and urea, differed among the three groups ( P<0.05). There were significant differences in vitamin B6 (0.960±0.249, 0.856±0.368, 1.319±0.322), galactose (0.888±0.171, 1.033±0.182, 1.127±0.127), lysine (1.551±0.924, 1.789±1.435, 0.541±0.424) and urea (0.743±0.142, 1.137±0.301, 1.171±0.457, respectively) levels among control group, D-NCP group and D-CP group ( F=5.90, P=0.008; F=5.59, P=0.009; F=4.26, P=0.025; F=5.29, P=0.012). Conclusions:The results indicated that dexamethasone induced cleft palate may be highly correlated with metabolic disorders including vitamin B6 metabolism, lysine metabolism, arginine anabolic metabolism and galactose metabolism.

Objective:To develop a new congenital cleft palate model suitable for the evaluation of cleft palate surgery and other related treatments.Methods:Ten New Zealand female rabbits (aged 40 weeks, 4.5-5.0 kg) were selected. The next day after mating with male rabbits of the same strain was regarded as the day 1 of gestation (GD1). Ten pregnant rabbits were enrolled with intramuscular injection 1.0 mg dosage of dexamethasone once a day from GD13 to GD16. The caesarean section was performed to obtain the newborn rabbits on GD31 for each pregnant rabbit. Then the rates of the survival and cleft palate rabbits were calculated. The rabbits were divided into two groups according to the method of random number table (10 non-cleft palate rabbits as the control group and 10 cleft palate rabbits as the experimental group). The body weights and physiological behaviors of the rabbits were evaluated and recorded at the age of 1, 2 and 4 weeks respectively after being fed by using standardized gastric tube feeding method. At 4 weeks old, three rabbits in each group were randomly selected for the observation of local anatomy of different layers of the mouth and upper jaw. The anatomical results were photographed for comparative analysis.Results:In this experiment, 48 infants of 10 pregnant rabbits survived under the condition with a survival rate of 66% (48/73), among which the incidence of cleft palate was 60% (29/48). All the rabbits in the control group and the experimental group were able to survive for at least 1 month with stable weight gain. There was no significant difference in weight ( P>0.05) and physiological appearance between the two groups. In cleft palate group, most of fetuses showed complete cleft palate with significant differences in the anatomical structure of the upper jaw compared with the control group including the changes in the morphology of the palatal mucosa, the terminal distribution of the soft palate muscles, and the dysplasia and absence of bone structures along the mid-maxillary line. Conclusions:In this study, it was the first time to successfully establish the dexamethasone-induced congenital cleft palate model in New Zealand rabbits for cleft surgical research.