There are four main mechanisms for the antibacterial action of antibiotics: inhibition of bacterial cell wall synthesis, interaction with cell membranes, interference with protein synthesis, and inhibition of nucleic acid replication and transcription.
Inhibition of cell wall synthesis
The cell wall of bacteria is mainly composed of polysaccharides, proteins and lipids, and has an important function of maintaining morphology, resisting changes in osmotic pressure, and allowing substances to pass. Therefore, inhibition of cell wall synthesis leads to bacterial cell rupture and death; mammalian cells are not affected by these drugs because they have no cell wall. This effect is dependent on a protein in the bacterial cell wall, commonly referred to as penicillin-binding proteins (PBPs), which bind to this protein and inhibit cell wall synthesis, so PBPs are also targets for such drugs. point. Antibacterial agents that act in this manner include penicillins and cephalosporins, but frequent use can result in increased resistance of the bacteria.
Interaction with cell membrane
Some antibiotics interact with the cell membrane of the cell to affect the permeability of the membrane, causing the leakage of important substances such as salt ions, proteins, nucleic acids and amino acids in the bacteria, which has a fatal effect on the cells. However, the bacterial cell membrane has several similarities with the basic structure of the human cell membrane, so this kind of antibiotic has certain toxicity to humans. Antibiotics that act in this way are polymyxin and brevisin.
Interfering protein synthesis
The synthesis of interfering proteins means that the enzymes necessary for cell survival cannot be synthesized. Antibiotics that act in this manner include fumycin (actinomycin), aminoglycosides, tetracyclines, and chloramphenicol. The synthesis of proteins is carried out on ribosomes, which consist of two subunits, 50S and 30S. Among them, aminoglycosides and tetracycline antibiotics act on the 30S subunit, while chloramphenicol, macrolides, lincomycins and the like mainly act on the 50S subunit, inhibiting the initial reaction of protein synthesis, and prolonging the peptide chain. Process and terminate the reaction.
Inhibition of nucleic acid replication and transcription
Inhibition of transcription and replication of nucleic acids can inhibit the function of bacterial nucleic acids, thereby preventing cell division and/or synthesis of desired enzymes. Antibiotics that act in this manner include nalidixic acid and dichloroacridine, and rifampin.