Cloning And Functional Analysis Of EriC~F Gene In Streptococcus Mutans Fluoride-resistant Strain

Objective:Dental caries is a common and frequently-occurring disease in oral cavity.Streptococcus mutans?S.mutans?is one of the most potent caries-causing bacteria with the highest detection rate.Fluoride has been extensively added to dental hygiene products because it can inhibit demineralization of hard tissue,promote its remineralization,and inhibit the growth and metabolism of cariogenic bacteria such as Streptococcus mutans.However,the emergence of fluoride-resistant strains not only reduces the anti-caries and anti-caries effects of fluoride,but also interferes with the normal structure and operation of oral microecosystems.By studying the mechanism of bacterial fluoride resistance,EriCF,a reverse fluoride transport protein,was proposed to be present in Streptococcus mutans,which belongs to F-/H+ reverse transport protein.It has special recognition and transportation function for fluoride ion.It can transport fluoride ion out of bacterial cells to weaken the toxic and side effects of fluoride ion on bacteria.EriCF protein in Streptococcus mutans is produced by coding two tandem homologous genes.The genes in GenBank are labeled SMU₁289c and SMU-1290c.However,little research has been done on fluoride resistance-related genes and coding proteins in fluoride-resistant strain UA159-FR of Streptococcus mrutans.Therefore,as a fluoride resistance-related protein closely related to the occurrence and development of dental caries,further study on the role of EriCF protein in fluoride-resistant strains of Streptococcus mutans and further explore the mechanism of fluoride resistance enhancement are of great significance for the research and development of stomatology.Methods:In this study,eriCF1 and eriCF2 genes of Streptococcus mutans fluoride-resistant strain UA159-FR were cloned and expressed to construct recombinant E.coli.The growth curves of recombinant E.coli in different NaF environments were drawn to explore the relationship between the differential expression of eriCFi and eriCF2 genes in Streptococcus mutans fluoride-resistant strain UA159-FR and the fluoride resistance of E.coli.Results:1.The eriCF1 and eriCF2 genes of Streptococcus mutans fluoride-resistant strain UA159-FR were successfully cloned and expressed in this experiment.At the same time,the recombinant E.coli containing the target gene was constructed.2.In the presence of the crcB gene of E.coli,the final concentration and growth rate of eriCF1 and eriCF2 wF2 higher than those of KZ?P<0.01?in high fluoride environment?3.0 g.L-1,2.5 g.L-1?and low fluoride environment?2.0 g.L-1,1.5 g.L-1?,and the final concentration of eriCF2 was higher than that of eriCF1?P<0.05?.3.Compared with the original E.coli BL21,the introduction of eriCF1 and eriCF2 not only enhanced the fluoride resistance of bacteria,but also enhanced the fluoride resistance of eriCF2.Conclusion:1.eriCF1 and eriCF2 genes in fluoride-resistant strains of Streptococcus mutans are related to the fluoride resistance of bacteria.2.Fluoride resistance-related proteins from different genera may have fluoride resistance superposition effect.3.Combination of EriCF1 and EriC-F2 protein with fluoride preparation can inhibit the growth and reproduction of Streptococcus mutans.