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Bacteria have a system that allows tetracyclines to be transported into the cell, whereas human cells do not. Human cells therefore are spared the effects of tetracycline on protein synthesis. [1] Tetracyclines retain an important role in medicine, although their usefulness has been reduced with the onset of antibiotic resistance. [2]
Tetracycline inhibits protein synthesis by blocking the attachment of charged tRNA at the P site peptide chain. Tetracycline blocks the A-site so that a hydrogen bond is not formed between the amino acids. Tetracycline binds to the 30S and 50S subunit of microbial ribosomes. [3] Thus, it prevents the formation of a peptide chain. [25]
There is still some debate in the field whether tetracycline derivatives alone can cause this conformational change or whether tetracycline must be in complex with magnesium to bind TetR. [4] (TetR typically binds tetracycline-Mg 2+ complexes inside bacteria, but TetR binding to tetracycline alone has been observed in vitro.) [citation needed]
β-Lactam antibiotics are indicated for the prevention and treatment of bacterial infections caused by susceptible organisms. At first, β-lactam antibiotics were mainly active only against gram-positive bacteria, yet the recent development of broad-spectrum β-lactam antibiotics active against various gram-negative organisms has increased their usefulness.
Oxytetracycline, like other tetracyclines, is used to treat many infections, both common and rare.Its better absorption profile makes it preferable to tetracycline for moderately severe acne at a dosage of 250–500 mg four times a day for usually six to eight weeks at a time, but alternatives should be sought if no improvement occurs by three months.
Puromycin is stable for one year as solution when stored at -20 °C. The recommended dose as a selection agent in cell cultures is within a range of 1-10 μg/mL, although it can be toxic to eukaryotic cells at concentrations as low as 1 μg/mL. Puromycin acts quickly and can kill more than 99% of nonresistant cells within one day. [citation needed]
Bacteriophages, also known as phages, infect and kill bacteria primarily during lytic cycles. [ 201 ] [ 200 ] Phages insert their DNA into the bacterium, where it is transcribed and used to make new phages, after which the cell will lyse, releasing new phage that are able to infect and destroy further bacteria of the same strain. [ 200 ]
Tetracycline-controlled transcriptional activation is a method of inducible gene expression where transcription is reversibly turned on or off in the presence of the antibiotic tetracycline or one of its derivatives (e.g. doxycycline).