Objective To investigate the differences in biofilm structure between LuxS-deficient strain and standard strain of Streptococcus mutans.Methods The standard strain of Streptococcus mutans and LuxS gene deficient strain were inoculated into the culture medium at a ratio of 1∶1 by using enamel grinding pieces as the carrier.After culture,the changes of colony morphology and growth curve of the two groups were observed,and the individual bacteria in the biofilm of the two groups were compared,and the structure of biofilm formed after 24 hours was compared.RT-PCR was used to detect the expression level of signal molecule autoinducer(AI)-2 mRNA in bacterial fluid.Results There was no significant phenotypic difference in colony morphology between the standard strain of Streptococcus mutans and the LuxS gene deficient strain.The overall changes in the growth curve of the two strains were consistent,and there were differences in the biofilm formed by the two strains.The standard strain of Streptococcus mutans formed a tighter biofilm structure,while the biofilm structure of the deficient strain was relatively sparse.RT-PCR detection showed that the AI-2 mRNA expression level of the LuxS gene deficient strain of Streptococcus mutans was lower than that of the standard strain,and the difference was statistically significant(P＜0.05).Conclusion The biofilm structure of Streptococcus mutans LuxS gene deficient strain is different from that of the standard strain in the in vitro model,and the LuxS gene deletion will affect the biofilm structure.
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