1. Inhibition of Transcription:
* Rifampicin: This antibiotic inhibits bacterial DNA-dependent RNA polymerase, preventing the transcription of DNA into mRNA, which is essential for protein synthesis.
2. Inhibition of Translation:
* Aminoglycosides (e.g., Gentamicin, Streptomycin): These antibiotics bind to the 30S ribosomal subunit, interfering with the initiation and accuracy of protein synthesis. They cause misreading of the mRNA codons, leading to the production of dysfunctional proteins.
* Tetracyclines (e.g., Tetracycline, Doxycycline): These antibiotics bind to the 30S ribosomal subunit and block the binding of aminoacyl-tRNA to the A site, preventing the addition of amino acids to the growing polypeptide chain.
* Macrolides (e.g., Erythromycin, Azithromycin): These antibiotics bind to the 50S ribosomal subunit and block the translocation step, preventing the movement of the ribosome along the mRNA and inhibiting peptide elongation.
* Chloramphenicol: This antibiotic binds to the 50S ribosomal subunit and inhibits the peptidyl transferase activity, preventing the formation of peptide bonds between amino acids.
3. Other Mechanisms:
* Oxazolidinones (e.g., Linezolid): These antibiotics bind to the 23S rRNA in the 50S ribosomal subunit, preventing the formation of the initiation complex and inhibiting the start of protein synthesis.
Important Notes:
* Selective Toxicity: Antibiotics are designed to target bacterial protein synthesis without affecting human protein synthesis. This is because bacteria and humans have significant differences in their ribosomes and other cellular machinery involved in protein synthesis.
* Resistance: Bacteria can develop resistance to antibiotics through various mechanisms, such as mutations in the target site, increased efflux pumps, or production of enzymes that inactivate the antibiotic.
* Bacterial Cell Death: Inhibition of protein synthesis eventually leads to the death of bacterial cells, as they are unable to produce essential proteins for growth and survival.
In summary: Antibiotics target different stages of protein synthesis in bacteria, disrupting their ability to produce functional proteins and leading to their death. Understanding the mechanisms of action of antibiotics is crucial for developing new drugs and combating antibiotic resistance.
