ABSTRACT
At the early stage of tooth development, the tooth embryo underwent three successive stages: bud stage, cap stage and bell stage through the interaction between epithelium and mesenchymal cells. During these stages, especially during the interphase transition, the presence of signal centers was particularly crucial. Signal center was composed of a small group of oral epithelial cell collections which were formed in a specific sequence, playing a decisive role in signal expression, morphogenesis and cell differentiation by secreting growth factors and other signaling molecules to regulate developmental signaling pathways. This paper reviews the evolution of signal centers as well as the important signal molecules and transcription factors in signal centers since the formation of dental placode.
ABSTRACT
Objective·To investigate the function of sahH gene in exopolysaccharides synthesis of Streptococcus mutans LuxS null strain. Methods·sahH+luxS-SmUA159 was constructed by introducing sahH gene into Streptococcus mutans LuxS null strain,while PIB169+luxS-SmUA159 and its wild strain SmUA159 were used as vector control and blank control. Real-time qPCR and anthrone test were performed to investigate the differences in exopolysaccharides synthesis among sahH+luxS-SmUA159, PIB169+luxS-SmUA159 and the wide-type strain SmUA159. Results·The transcriptional levels of gtfA and gtfD were upregulated in the sahH+luxS-SmUA159,compared to SmUA159 and PIB169+luxS-SmUA159(both P<0.05),but there was no statistical difference in the transcriptional levels of gtfB and gtfC.The results of the anthrone test showed exopolysaccharides synthesis of the three groups was also similar. Conclusion·sahH gene affects the expression of some genes related to exopolysaccharides synthesis,but it has little effect on the whole content of bacterial exopolysaccharides.
ABSTRACT
The objective of this study was to investigate the compositional profiles and microbial shifts of oral microbiota during head-and-neck radiotherapy. Bioinformatic analysis based on 16S rRNA gene pyrosequencing was performed to assess the diversity and variation of oral microbiota of irradiated patients. Eight patients with head and neck cancers were involved in this study. For each patient, supragingival plaque samples were collected at seven time points before and during radiotherapy. A total of 147,232 qualified sequences were obtained through pyrosequencing and bioinformatic analysis, representing 3,460 species level operational taxonomic units (OTUs) and 140 genus level taxa. Temporal variations were observed across different time points and supported by cluster analysis based on weighted UniFrac metrics. Moreover, the low evenness of oral microbial communities in relative abundance was revealed by Lorenz curves. This study contributed to a better understanding of the detailed characterization of oral bacterial diversity of irradiated patients.
Subject(s)
Humans , Middle Aged , Actinomyces , Classification , Radiation Effects , Actinomycetaceae , Classification , Radiation Effects , Alcaligenaceae , Classification , Radiation Effects , Bacteria , Classification , Radiation Effects , Capnocytophaga , Classification , Radiation Effects , Carnobacteriaceae , Classification , Radiation Effects , Computational Biology , Dental Plaque , Microbiology , Follow-Up Studies , Gemella , Classification , Radiation Effects , Head and Neck Neoplasms , Radiotherapy , High-Throughput Nucleotide Sequencing , Neisseria , Classification , Radiation Effects , Prevotella , Classification , Radiation Effects , Propionibacteriaceae , Classification , Radiation Effects , RNA, Bacterial , RNA, Ribosomal, 16S , Streptococcus , Classification , Radiation Effects , Veillonella , Classification , Radiation EffectsABSTRACT
<p><b>AIM</b>The purpose of this study was to develop a mathematical model to quantitatively describe the passive transport of macromolecules within dental biofilms.</p><p><b>METHODOLOGY</b>Fluorescently labeled dextrans with different molecular mass (3 kD, 10 kD, 40 kD, 70 kD, 2000 kD) were used as a series of diffusion probes. Streptococcus mutans, Streptococcus sanguinis, Actinomyces naeslundii and Fusobacterium nucleatum were used as inocula for biofilm formation. The diffusion processes of different probes through the in vitro biofilm were recorded with a confocal laser microscope.</p><p><b>RESULTS</b>Mathematical function of biofilm penetration was constructed on the basis of the inverse problem method. Based on this function, not only the relationship between average concentration of steady-state and molecule weights can be analyzed, but also that between penetrative time and molecule weights.</p><p><b>CONCLUSION</b>This can be used to predict the effective concentration and the penetrative time of anti-biofilm medicines that can diffuse through oral biofilm. Furthermore, an improved model for large molecule is proposed by considering the exchange time at the upper boundary of the dental biofilm.</p>
Subject(s)
Actinomyces , Algorithms , Biofilms , Biological Transport , Dental Plaque , Microbiology , Dextrans , Pharmacokinetics , Diffusion , Fluorescent Dyes , Pharmacokinetics , Fusobacterium nucleatum , Macromolecular Substances , Pharmacokinetics , Microscopy, Confocal , Models, Biological , Molecular Probe Techniques , Streptococcus mutans , Streptococcus sanguisABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of Streptococcus mutans luxS mutarotation on the early biofilm formation.</p><p><b>METHODS</b>Based on the immobilization of magnetic beads by adherent cells, an assay of biofilm quantitative analysis was developed for the kinetic quantification of biofilm formation in this study. Streptococcus mutans luxS mutant strain was constructed and subject to this biofilm luxS mutant strain were compared.</p><p><b>RESULTS</b>The delta luxS mutant started to form a biofilm from the 6th hour (delta BFI = 2.015), and the delta BFI of luxS mutant increased more quickly than that of the wild type strain, until reaching a complete immobilization of the beads after 10 hours (delta BFI = 7.025). The wild-type strain start to form a biofilm from the 10 th hour (delta BFI = 1.875) and the beads were completely immobilized between 12 and 14 hours.</p><p><b>CONCLUSIONS</b>The luxS mutation can accelerate biofilm on a polystyrene surface during the mid-exponential growth phase. And a luxS-dependent signal may play an important role in the early biofilm formation of Streptococcus mutans.</p>
Subject(s)
Bacterial Proteins , Genetics , Biofilms , Carbon-Sulfur Lyases , Genetics , Gene Deletion , Gene Expression Regulation, Bacterial , Streptococcus mutans , GeneticsABSTRACT
<p><b>OBJECTIVE</b>It is reported that Streptococcus mutans luxS gene may have an important role in the interspecies quorum sensing system. To construct the S. mutans luxS gene knockout mutant, this research aim to construct the luxS gene allelic exchange plasmid.</p><p><b>METHODS</b>The upstream and downstream flank DNA fragments of S. mutans luxS gene (Xup, Xdn)and the E. coli kanamycin resistance gene (Kana) were enriched by pfu DNA polymerase with "nest PCR" methods. These fragments were ligated into pBluescript SK (+) Phagemids vector with double endonuclease reaction sequentially.</p><p><b>RESULTS</b>With endonuclease reaction and DNA sequencing, it was proved that the objective plasmid, Xukd-pbsk, was constructed correctively and the kanamycin resistance gene could be expressed in vitro.</p><p><b>CONCLUSION</b>The S. mutans luxS gene allelic exchange plasmid is constructed correctively in this research and can be used in the future research of S. mutans luxS gene knockout mutant.</p>
Subject(s)
Bacterial Proteins , Carbon-Sulfur Lyases , Escherichia coli , Genetic Vectors , Plasmids , Polymerase Chain Reaction , Quorum Sensing , Streptococcus mutansABSTRACT
<p><b>OBJECTIVE</b>To compare the antibacterial effect between sodium fluoride and Galla Chinesis in bioflim model. To evaluate the feasibility of application of Gala Chinesis in the clinical practice of caries prevention.</p><p><b>METHODS</b>Streptococcus mutans, Streptococcus sanguis, Streptococcus salivarius and Actinomyces naeslundii had been chosen as the experimental bacteria. In the experiment, biofilmn model was constructed, and two agents were added in the media. After a period of continuous culture, the number of bacteria adhering on the HA disc was examed, the planktonic pH in the flow cell was recorded continuously, and the morphology of the biofilmn formed on the HA disc was observed by SEM.</p><p><b>RESULTS</b>(1) Galla Chinesis could inhibit the growth of the four oral bacteria in the biofilm just as sodium fluoride. (2) Galla Chinesis and sodium fluoride could prevent the descent of the planktonic pH in the flow cell, but Galla Chinesis was less efficient than sodium fluoride. (3) The biofilms formed after application of Galla Chinesis and fluoride, but the bacterial cells had less matrix than those applicated with sucrose.</p><p><b>CONCLUSION</b>Galla Chinesis is one kind of effective cariostatic natural agents.</p>