Preliminary Analysis on Functions of hit Gene in Streptococcus Mutans and Its Impact on Cariogenicity

doi:10.13701/j.cnki.kqyxyj.2023.07.006

Abstract

Abstract: Objective: To investigate the function of hit gene and its effect on the cariogenicity of Streptococcus mutans. Methods: LFH-PCR was employed to construct the hit-deficient mutant strain (Smu.Δhit). The hit gene complemented strain (Smu.ΔhitC) and its added eGFP tagging strain (Smu.ΔhitC-eGFP) were also constructed. The growth rate and acid resistance with different pH values, the biofilm formation, as well as the morphology of the Smu.Δhit and its parental strains were compared. In vitro detection of artificial caries-like lesions of the Smu.Δhit on human dental enamel surfaces was performed. Results: The Smu.Δhit,Smu.ΔhitC, and Smu.ΔhitC-eGFP were successfully screened out. The growth rate of the Smu.Δhit versus their parental was increased greatly in BHI medium. When subjected to modified BHI medium (pH 5.6), the growth inhibition of the Smu.Δhit was much less than that of ATCC25175. Compared with ATCC25175, scanning electron microscopy (SEM), crystalline violet staining, and anthrone-sulfuric acid test analysis showed that deficiency of hit caused alterations in morphology and decreased in biofilm formation, being devoid of extracellular glucans. Much more serious artificial caries-like lesions of the Smu.Δhit on human dental enamel surfaces was also rapidly occurred. Conclusion: The hit gene is growth-phase regulated in the cell-cycle, and has significant impact on the growth rate, biofilm formation, and acid resistance, and rapidly causes caries-like lesions on human dental enamel surfaces.

Key words: Streptococcus mutans, ATCC25175, hit gene, cariogenicity, hit-like protein

FAN Zixuan, QIAO Li, LAI Yangfan, WANG Peng, JIANG Dairen, LIANG Yan, YE Zhaoyang, LUO Peng. Preliminary Analysis on Functions of hit Gene in Streptococcus Mutans and Its Impact on Cariogenicity[J]. Journal of Oral Science Research, 2023, 39(7): 594-601.

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