Analyze the antibacterial mechanism of Nisin

Nisin, namely nisin, is a polypeptide antibiotic substance produced by Streptococcus lactis. The pore - forming theory holds that nisin exerts its antibacterial effect mainly by forming pores in the bacterial cell membrane. The specific process and related applications are as follows:

Adsorption and pore formation: Nisin is positively charged, while the surface of the bacterial cell membrane is usually negatively charged. Through electrostatic interaction, it can be adsorbed onto the bacterial cell membrane. Then, the C - terminal and N - terminal of the amino acids in Nisin combine with the phosphate ester layer on the cell membrane, and then penetrate into the bacterial cell membrane. Multiple nisin molecules gather together to form permeable pores in the cell membrane.

Destruction of cell membrane function: After the pores are formed, the integrity of the bacterial cell membrane will be damaged, leading to the imbalance of proton motive force and pH value. Small molecular weight hydrophilic substances such as potassium ions will flow out of the cytoplasm, and the cell membrane will be depolarized. At the same time, ATP in the cell membrane leaks, some small molecules and ions will also be lost, while water molecules outside the cell membrane will enter the cell.

Causing bacterial death: Due to the change of osmotic pressure inside and outside the cell membrane, the bacterial cells will absorb water and swell, and finally autolyze and die.

Based on the pore - forming theory, the antibacterial effect of nisin can be enhanced in some ways in practical applications. For example, coating it with chitosan/sodium alginate microspheres can make it act on the bacterial cell membrane more stably, form pores more effectively, and significantly enhance the inhibitory effect on bacteria such as Staphylococcus aureus. In addition, understanding the pore - forming antibacterial mechanism of nisin is helpful to better play its role in food preservation, medicine and other fields. For instance, when it is used in root canal irrigation, oral health care, etc., it can specifically inhibit related pathogenic bacteria and reduce the impact on normal human cells.