Bacterial viruses, also known as bacteriophages or phages, infect bacteria by attaching to them, injecting their genetic material, hijacking the bacterial cell's machinery to replicate, and then bursting the cell open to release new viruses.
Here's a more detailed breakdown:
The Bacteriophage Life Cycle
The life cycle of a bacteriophage typically follows these steps:
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Attachment (Adsorption): The phage attaches to specific receptors on the surface of the bacterial cell. This specificity is crucial; a phage can only infect bacteria that possess the correct receptor.
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Penetration (Injection): The phage injects its genetic material (DNA or RNA) into the bacterial cell. The capsid (the protein coat of the phage) usually remains outside the bacterium.
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Replication: Once inside, the phage's genetic material takes over the bacterial cell's machinery. The bacterial cell begins to produce copies of the phage's DNA or RNA, as well as phage proteins.
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Assembly: The newly synthesized phage components (DNA/RNA and proteins) are assembled into new, complete phage particles.
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Lysis (Release): The newly formed phages are released from the bacterial cell. This usually happens by lysis, where the phage produces an enzyme that breaks down the bacterial cell wall, causing the cell to burst open and release the new phages. This lytic cycle then repeats, with the new phages infecting other bacteria.
Two Main Types of Phage Life Cycles:
There are two main types of bacteriophage life cycles: the lytic cycle and the lysogenic cycle. Some phages can only follow the lytic cycle, while others can switch between the two.
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Lytic Cycle: This is the cycle described above, which culminates in the lysis (bursting) of the bacterial cell and the release of new phages.
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Lysogenic Cycle: In this cycle, the phage DNA integrates into the bacterial chromosome. The integrated phage DNA is called a prophage. The bacterium continues to live and reproduce normally, and every daughter cell inherits a copy of the prophage. At some point, triggered by environmental stressors, the prophage can excise itself from the bacterial chromosome and enter the lytic cycle.
Significance of Bacteriophages
Bacteriophages play an important role in bacterial populations and have potential applications in:
- Phage Therapy: Using phages to treat bacterial infections, particularly those resistant to antibiotics.
- Bacterial Detection: Phages can be used to detect the presence of specific bacteria in samples.
- Genetic Engineering: Phages can be used as vectors to deliver genes into bacteria.
