Antimicrobial activity, stability, cytotoxicity and mechanism of action determination of antimicrobial peptide against Bacillus cereus improved by cyclization

Main Article Content

Natthaporn Klubthawee
Patcharin Khajornpipat

Abstract

Abstract


Bacillus cereus is a food-borne pathogenic bacteria found in various food products that can produce heat-resistant endospores and toxins. Nowadays, the emergence of antibiotic resistance caused by B. cereus has increased. Because of their bioactive properties, broad-spectrum antimicrobial activities against a wide range of pathogenic bacteria and low propensity to induce drug-resistant development, antimicrobial peptides (AMPs) are considered a new source of potential candidates for the development of novel antimicrobial agents. However, there are some limitations for applications, including low stability due to proteolytic degradation, cation of salt impediment, and heat denaturation. These limitations can be overcome by peptide modification such as cyclization. The aim of this study, therefore, was to determine the antimicrobial activity, stability, cytotoxicity, and mechanism of action of peptides improved by cyclization (cyclic PA) compared with PA parental peptide. The antimicrobial activity was determined by broth microdilution and the results demonstrated that cyclic PA was as active as PA peptide against Bacillus cereus ATCC11778, with MIC and MBC values of 7.81 µg/mL. The results from the stability test demonstrated that both peptides showed strong heat stability even at 100 °C. However, cyclic PA showed more stability than PA against pepsin digestion and hindrance from cation salts. In addition, the cyclic PA exhibited no cytotoxicity at all tested concentrations, while the PA peptide showed statistically significant cytotoxicity at concentrations of ≥31.25 µg/mL. Flow cytometric analysis results indicated that PA and cyclic PA peptides induced high levels of membrane depolarization and permeabilization (97.89 ± 2.73% and 99.50 ± 0.56%, respectively) at their MICs. In conclusion, the modification of peptides by cyclization could be used to improve the stability and reduce the toxicity of AMPs. Our study also highlighted the potential of cyclic PA peptide for the development of novel antimicrobial agents in the future.


Keywords: Antimicrobial peptides, Cyclization, Stability, Cytotoxicity, Mechanism of action

Article Details

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Research Articles

References

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