Studies Of The Effects Of Mutacin Extract On The Main Bacteria Of Plaque Biofilms

Plaque biofilms, a well-organized microbial community on dental surface, is a major etiological factor of caries. Compared with planktonic bacteria, the bacteria in biogilms have the different gene expression and phenotype,as well as have an increased resistance to antimicrobials. S.mutans is the most important bacteria which can lead to caries. Mutacin is one of the bacteriocin which produced by S.mutans. It can hold back different strains of same bacteria and other similarity type bacteria in order to retain itself need. And it is an important instrument in living competition. This experiment used solid-phase synthesis . In vitro experiment, animal experiment to synthesis primary structure of mutacinâ… ,â…¢and 8 short peptides and to detect its active group.1. Study of the contrivance and synthesls of mutacinâ… ,â…¢and short peptides.The peptide mutacin from S.mutans was synthesized by Merrifold peptide synthesor and its amino acid sequence was detected by Fast technique. The synthesis of mutacinâ… ,â…¢makes it possible to study its immunologic characteristics. 24 and 22 polypeptides with purity of 80% were precisely synthesized. The successful synthesis of mutacinâ… ,â…¢and short peptides makes it possible to study its immunologic characteristics.2. Study of in vitro experiment on the antimicrobial effects of peptide mutacin from S.mutans.Study the in vitro antimicrobial activity of peptide mutacinâ… ,â…¢and short peptides to seach the active group. The peptide mutacin from S.mutans was synthesized by Merrifold peptide synthesor and its amino acid sequence was detected by Fast technique. The antibiotic activities of peptide mutacinâ… ,â…¢and short peptides against Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguis, Actinomyces naeslundi, Actinomyces viscosus,Veillonella were tested by drug sensitive slips method and tube double dilution method. The minimal inhibitory concentrations shows that peptides effect on the Streptococcus mutans is 50%,that mean it minimal inhibitory concentrations is 0.5mmol/ml . But there is no bactericidal activity of short peptides on the Streptococcus mutans. The peptide mutacinâ… ,â…¢and short peptides only have the bactericidal activity against Streptococcus mutans, Streptococcus sobrinus and Streptococcus sanguis. The minimal inhibitory concentrations shows that No.3 short peptide and No.8 short peptide against the Streptococcus sanguis is 50%, there is no bactericidal activity of other short peptides against the Streptococcus sanguis. The peptide mutacinâ… ,â…¢and two short peptides have the bactericidal activity. The peptide mutacinâ… ,â…¢and two short peptides may be the active group.3. Studies on in vivo anti-microbial activities of the short peptides from mutacinâ… ,â…¢.Using of the short peptides to observe the growth of intraoral bacteria plaque of rat. We choose the SD rat, adaptivity feeding them one week , then divide into four groups randomly, inuncion experiment medicine regularity. Observe the change of the areas of bacteria plaque from the rats'maxliary molar in four groups, and use Photoshop and VC++6.0 to statistics it.The result show that the areas of bacteria plaquethe of the group of activity peptides rat was smaller than before. Observation, gum wasn't flare.According to the result we can infer that the activity short peptides can restrain the growth of bacteria plaque and have no mucosa toxicity.