| ObjectiveThe aim of this study was to investigate the level of D-alanylated of Lipoteichoic acid（LTA）,surface charge,cell surface hydrophobicity of different Streptococcus mutans（S.mutans）,including standard strain SM ATCC 25175,SM 593（isolated from caries-active adults）and SM 18（isolated from caries-free adults）.The relationship between the level of D-alanylated of LTA,surface charge,cell surface hydrophobicity and cariogenic ability of different S.mutans were analyzed.The relationship between the level of D-alanylated of LTA and the surface charge and hydrophobicity were also detected.Methods（1）The sample extracted from SM ATCC 25175 by butanol was compared with the LTA standard by Fourier transform infrared spectroscopy（FT-IR）in order to identify the sample.（2）After identifying the sample,the LTA were isolated from SM 593,SM ATCC25175,and SM 18 by the same methods.D-alanine and phosphorus contents of LTA were detected to analyze the molar ratio of D-alanine to phosphorus.The dlt ABCD gene of SM 593,SM ATCC 25175,and SM 18 were evaluated by Real-Time PCR to assess the level of D-alanylated of LTA at the same time.（3）The distribution of surface charge and cell surface hydrophobicity of SM 593,SM ATCC 25175,and SM 18 were evaluated by cytochrome c and microbial adhesion to hydrocarbons.Results（1）The sample extracted from SM ATCC 25175 was compared with the standard LTA by FT-IR.The absorption peaks in the characteristic frequency region and the fingerprint region were the same,and the functional groups including-NH,-CH2,-CH3,-C=O,-C=H,-P=O,-C-O were the same.（2）Statistical analysis showed the molar ratio of D-alanine to phosphorus of SM593 was higher than SM ATCC 25175 and SM 18.The molar ratio of D-alanine to phosphorus in SM 18 was lowest.Real-Time PCR results showed that the expression level of dlt ABCD in SM 18 was lowest（P<0.05）.The expression of dlt ABCD gene in SM 593 was highest（P<0.05）.No significant difference was observed in the expression level of dlt D gene between SM 18 and SM ATCC 25175（P>0.05）.（3）Microbial adhesion to hydrocarbons results of these three S.mutans showed that the rate of adherence to hydrocarbons of SM 18 was lower than SM 593 and SM ATCC 25175（P<0.05）.But there was no significant difference between SM593 and SM ATCC 25175（P>0.05）.As for the surface charge,SM ATCC 25175had more positively charged cell envelope than SM 593 and SM 18（P<0.05）.No significant difference was observed in SM 593 and SM 18（P>0.05）.Conclusion（1）LTA from S.mutans could be isolated by butanol.（2）The level of D-alanylated of LTA of SM 593 was higher than SM ATCC 25175and SM 18.The level of D-alanylated of LTA may influence the cariogenic ability of different S.mutans.（3）The level of cell surface hydrophobicity and surface charge was different in S.mutans which had different cariogenic ability.The level of D-alanylated of LTA may affect the surface charge and hydrophobicity of S.mutans.But it was not the determinant factor.These findings indicated that the level of D-alanylated of LTA,cell surface hydrophobicity and surface charge of different S.mutans may affect their cariogenic ability.These findings also provide the theoretical basis for further study of the cariogenic mechanism of S.mutans. |
