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Tetracycline-controlled gene expression is based upon the mechanism of resistance to tetracycline antibiotic treatment found in gram-negative bacteria. In nature, the P tet promoter expresses TetR (the repressor ) and TetA, the protein that pumps tetracycline antibiotic out of the cell.
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]
Phages destroy bacterial cell walls and membrane through the use of lytic proteins which kill bacteria by making many holes from the inside out. [272] Bacteriophages can even possess the ability to digest the biofilm that many bacteria develop that protect them from antibiotics in order to effectively infect and kill bacteria.
Narrow-spectrum antibiotics have low propensity to induce bacterial resistance and are less likely to disrupt the microbiome (normal microflora). [3] On the other hand, indiscriminate use of broad-spectrum antibiotics may not only induce the development of bacterial resistance and promote the emergency of multidrug-resistant organisms, but also cause off-target effects due to dysbiosis.
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 ]
The microbial food web refers to the combined trophic interactions among microbes in aquatic environments. These microbes include viruses, bacteria, algae, heterotrophic protists (such as ciliates and flagellates). [1] In aquatic ecosystems, microbial food webs are essential because they form the basis for the cycling of nutrients and energy.
Oxytetracycline is a broad-spectrum tetracycline antibiotic, the second of the group to be discovered. Oxytetracycline works by interfering with the ability of bacteria to produce essential proteins. Without these proteins, the bacteria cannot grow, multiply and increase in numbers.
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.