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An in vitro study on the effect of free amino acids alone or in combination with nisin on biofilms as well as on planktonic bacteria of Streptococcus mutans.

Tong Z, Zhang L, Ling J, Jian Y, Huang L, Deng D - PLoS ONE (2014)

Bottom Line: The results of the MIC and MBC analyses showed that D-cysteine (Cys), D- or L-aspartic acid (Asp), and D- or L-glutamic acid (Glu) significantly improve the antibacterial activity of nisin against S. mutans and that the mixture of D-Cys, D-Asp, and D-Glu (3D-AAs) and the mixture of L-Cys, L-Asp, and L-Glu (3L-AAs) at a concentration of 40 mM can prevent S. mutans growth.Crystal violet staining showed that the D- or L-enantiomers of Cys, Asp, and Glu at a concentration of 40 mM can inhibit the formation of S. mutans biofilms, and their mixture generated a stronger inhibition than the components alone.Furthermore, the mixture of the three D-AAs or L-AAs may improve the antibacterial activity of nisin against S. mutans biofilms.

View Article: PubMed Central - PubMed

Affiliation: Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China; Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.

ABSTRACT
Free D-amino acids (D-AAs) are one of the most striking features of the peptidoglycan composition in bacteria and play a key role in regulating and disassembling bacterial biofilms. Previous studies have indicated that the antimicrobial peptide nisin can inhibit the growth of the cariogenic bacteria Streptococcus mutans. The present study investigated the effect of free amino acids either alone or in combination with nisin on biofilm and on planktonic S. mutans bacteria. The results of the MIC and MBC analyses showed that D-cysteine (Cys), D- or L-aspartic acid (Asp), and D- or L-glutamic acid (Glu) significantly improve the antibacterial activity of nisin against S. mutans and that the mixture of D-Cys, D-Asp, and D-Glu (3D-AAs) and the mixture of L-Cys, L-Asp, and L-Glu (3L-AAs) at a concentration of 40 mM can prevent S. mutans growth. Crystal violet staining showed that the D- or L-enantiomers of Cys, Asp, and Glu at a concentration of 40 mM can inhibit the formation of S. mutans biofilms, and their mixture generated a stronger inhibition than the components alone. Furthermore, the mixture of the three D-AAs or L-AAs may improve the antibacterial activity of nisin against S. mutans biofilms. This study underscores the potential of free amino acids for the enhancement of the antibacterial activity of nisin and the inhibition of the cariogenic bacteria S. mutans and biofilms.

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Related in: MedlinePlus

Effect of 3D-AAs and 3L-AAs on S. mutans growth.All of the determinations were repeatedly performed three times on different days. The y-axis represents the survival count of bacteria (mean ± SD), and the x-axis represents the time after the challenge with amino acids. “*” indicates a significant difference in the S. mutans survival count between the amino acid challenge groups and the control, and a value of p<0.00625 was considered significant; “#” indicates a significant difference in the S. mutans survival count between the 3D-AA and 3L-AA challenge groups, and a value of p<0.05 was considered to be significant.
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pone-0099513-g001: Effect of 3D-AAs and 3L-AAs on S. mutans growth.All of the determinations were repeatedly performed three times on different days. The y-axis represents the survival count of bacteria (mean ± SD), and the x-axis represents the time after the challenge with amino acids. “*” indicates a significant difference in the S. mutans survival count between the amino acid challenge groups and the control, and a value of p<0.00625 was considered significant; “#” indicates a significant difference in the S. mutans survival count between the 3D-AA and 3L-AA challenge groups, and a value of p<0.05 was considered to be significant.

Mentions: In the time-kill assay, the 3D-AAs at their respective concentration of 40 mM was the most effective treatment for the inhibition of S. mutans of all of the experimental groups, and the S. mutans survival rates showed a significant reduction from 4 h to 24 h of challenge, but 3L-AAs exhibited no significant effect after 4 h of challenge. Both treatments showed significant differences at the same time points (p<0.05). The adjustment of 3D-AAs and 3L-AAs pH 7 resulted in decreases in the S. mutans survival rate after 8, 12, and 24 h of challenge. Significant differences were found between the different experimental groups at 40 mM and the control at the same time point, with the exception of 3D-AAs and 3L-AAs pH 7 at 4 h after challenge (p<0.00625). Furthermore, both 3D-AAs and 3L-AAs at concentrations of 10 mM or 5 mM did not significantly decrease the S. mutans survival rates (Fig. 1).


An in vitro study on the effect of free amino acids alone or in combination with nisin on biofilms as well as on planktonic bacteria of Streptococcus mutans.

Tong Z, Zhang L, Ling J, Jian Y, Huang L, Deng D - PLoS ONE (2014)

Effect of 3D-AAs and 3L-AAs on S. mutans growth.All of the determinations were repeatedly performed three times on different days. The y-axis represents the survival count of bacteria (mean ± SD), and the x-axis represents the time after the challenge with amino acids. “*” indicates a significant difference in the S. mutans survival count between the amino acid challenge groups and the control, and a value of p<0.00625 was considered significant; “#” indicates a significant difference in the S. mutans survival count between the 3D-AA and 3L-AA challenge groups, and a value of p<0.05 was considered to be significant.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4060998&req=5

pone-0099513-g001: Effect of 3D-AAs and 3L-AAs on S. mutans growth.All of the determinations were repeatedly performed three times on different days. The y-axis represents the survival count of bacteria (mean ± SD), and the x-axis represents the time after the challenge with amino acids. “*” indicates a significant difference in the S. mutans survival count between the amino acid challenge groups and the control, and a value of p<0.00625 was considered significant; “#” indicates a significant difference in the S. mutans survival count between the 3D-AA and 3L-AA challenge groups, and a value of p<0.05 was considered to be significant.
Mentions: In the time-kill assay, the 3D-AAs at their respective concentration of 40 mM was the most effective treatment for the inhibition of S. mutans of all of the experimental groups, and the S. mutans survival rates showed a significant reduction from 4 h to 24 h of challenge, but 3L-AAs exhibited no significant effect after 4 h of challenge. Both treatments showed significant differences at the same time points (p<0.05). The adjustment of 3D-AAs and 3L-AAs pH 7 resulted in decreases in the S. mutans survival rate after 8, 12, and 24 h of challenge. Significant differences were found between the different experimental groups at 40 mM and the control at the same time point, with the exception of 3D-AAs and 3L-AAs pH 7 at 4 h after challenge (p<0.00625). Furthermore, both 3D-AAs and 3L-AAs at concentrations of 10 mM or 5 mM did not significantly decrease the S. mutans survival rates (Fig. 1).

Bottom Line: The results of the MIC and MBC analyses showed that D-cysteine (Cys), D- or L-aspartic acid (Asp), and D- or L-glutamic acid (Glu) significantly improve the antibacterial activity of nisin against S. mutans and that the mixture of D-Cys, D-Asp, and D-Glu (3D-AAs) and the mixture of L-Cys, L-Asp, and L-Glu (3L-AAs) at a concentration of 40 mM can prevent S. mutans growth.Crystal violet staining showed that the D- or L-enantiomers of Cys, Asp, and Glu at a concentration of 40 mM can inhibit the formation of S. mutans biofilms, and their mixture generated a stronger inhibition than the components alone.Furthermore, the mixture of the three D-AAs or L-AAs may improve the antibacterial activity of nisin against S. mutans biofilms.

View Article: PubMed Central - PubMed

Affiliation: Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China; Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.

ABSTRACT
Free D-amino acids (D-AAs) are one of the most striking features of the peptidoglycan composition in bacteria and play a key role in regulating and disassembling bacterial biofilms. Previous studies have indicated that the antimicrobial peptide nisin can inhibit the growth of the cariogenic bacteria Streptococcus mutans. The present study investigated the effect of free amino acids either alone or in combination with nisin on biofilm and on planktonic S. mutans bacteria. The results of the MIC and MBC analyses showed that D-cysteine (Cys), D- or L-aspartic acid (Asp), and D- or L-glutamic acid (Glu) significantly improve the antibacterial activity of nisin against S. mutans and that the mixture of D-Cys, D-Asp, and D-Glu (3D-AAs) and the mixture of L-Cys, L-Asp, and L-Glu (3L-AAs) at a concentration of 40 mM can prevent S. mutans growth. Crystal violet staining showed that the D- or L-enantiomers of Cys, Asp, and Glu at a concentration of 40 mM can inhibit the formation of S. mutans biofilms, and their mixture generated a stronger inhibition than the components alone. Furthermore, the mixture of the three D-AAs or L-AAs may improve the antibacterial activity of nisin against S. mutans biofilms. This study underscores the potential of free amino acids for the enhancement of the antibacterial activity of nisin and the inhibition of the cariogenic bacteria S. mutans and biofilms.

Show MeSH
Related in: MedlinePlus