Targeting the Bacterial Cell
Bacteriophages are specialized viruses that exclusively infect bacterial cells. They begin the infection process by searching for a suitable host cell. Each bacteriophage has tail fibers that are specifically adapted to recognize and bind to certain receptor sites on the surface of a bacterial cell. This ensures that the bacteriophage attaches only to specific types of bacteria.
Attachment and Binding
Once a bacteriophage finds a compatible bacterial cell, its tail fibers lock onto the bacterial surface. This binding is highly specific, almost like a key fitting into a lock. The tail fibers adjust their position to secure a tight fit, ensuring that the bacteriophage is perfectly anchored to the bacterial cell.
Injection of Genetic Material
Following a successful attachment, the bacteriophage prepares to inject its genetic material into the bacterial cell. The bacteriophage contracts its tail sheath, a process that drives the tail tube through the bacterial cell wall and membrane. Through this tube, the bacteriophage injects its DNA (or RNA in some cases) directly into the bacterial cytoplasm.
Hijacking the Cellular Machinery
Once inside the host cell, the bacteriophage’s genetic material takes control of the bacterial cell’s machinery. The viral DNA integrates into the bacterial genome or exists independently within the cell and begins directing the cell’s operations. The primary goal is to use the bacterial resources to replicate the bacteriophage’s genetic material and to manufacture new viral components.
Replication and Assembly
The bacterial cell, now reprogrammed by the bacteriophage DNA, starts producing viral proteins and replicating the viral genome. These components are then assembled into new bacteriophage particles within the bacterial cell. This assembly process is highly efficient, producing numerous new viruses in a relatively short time.
Cell Lysis and Release of New Viruses
As new bacteriophages accumulate inside the bacterial cell, the host cell becomes filled to capacity and eventually bursts open in a process called lysis. This cell bursting releases the newly formed bacteriophages into the environment, where they can seek out new bacterial hosts to infect. The cycle then repeats, spreading the bacteriophage to additional bacteria.
Watch the full video; it contains a detailed, step-by-step explanation.
Frequently Asked Questions:
What is a bacteriophage?
- A bacteriophage is a type of virus that specifically infects and replicates within bacteria.
How does a bacteriophage recognize a bacterial cell?
- A bacteriophage recognizes a bacterial cell by its tail fibers, which bind to specific receptor sites on the surface of the bacteria.
What happens after a bacteriophage attaches to a bacterial cell?
- After attachment, the bacteriophage injects its genetic material, either DNA or RNA, into the bacterial cell.
What is the role of the bacteriophage’s tail sheath during infection?
- The tail sheath contracts to drive the tail tube through the bacterial cell wall, allowing the injection of viral genetic material.
How does bacteriophage DNA affect the bacterial cell?
- The bacteriophage DNA takes control of the bacterial cell’s machinery, directing it to replicate the viral genome and produce viral components.
What is the process called when a bacteriophage forces a bacterial cell to produce new viruses?
- This process is known as replication and assembly.
What happens to the bacterial cell after it is filled with new bacteriophages?
- The bacterial cell bursts open in a process called lysis, releasing the new bacteriophages.
What is the significance of bacteriophages in medical research?
- Bacteriophages are studied for their potential use in treating bacterial infections, especially those resistant to antibiotics.
Can bacteriophages infect human cells?
- No, bacteriophages specifically target bacterial cells and do not infect human cells.
What is the difference between lytic and lysogenic cycles in bacteriophages?
- In the lytic cycle, bacteriophages reproduce and cause the host cell to burst. In the lysogenic cycle, the phage DNA integrates into the host genome and replicates along with it without causing immediate lysis.
How do bacteriophages contribute to horizontal gene transfer?
- Bacteriophages can transfer genetic material between bacteria through transduction, which plays a role in the spread of antibiotic resistance.
What is a tail fiber in the context of a bacteriophage?
- Tail fibers are structures that help the bacteriophage attach to the specific receptors on a bacterial cell’s surface.
What ensures the bacteriophage injects its DNA into the bacterial cell?
- The precise fit and anchoring of the tail fibers to the bacterial surface ensure the effective injection of DNA into the cell.
What is meant by ‘bacterial cell’s machinery’?
- It refers to the cell’s mechanisms and structures involved in gene expression, energy production, and other metabolic processes.
Why does the bacteriophage DNA not always integrate into the bacterial genome?
- Some bacteriophages exist as separate plasmids within the bacterial cell, using the host’s machinery without integrating into the genome.
What triggers the lysogenic to lytic switch in temperate bacteriophages?
- Environmental stress or certain chemical signals can trigger a temperate bacteriophage to switch from the lysogenic to the lytic cycle.
What is a prophage?
- A prophage is the form of the bacteriophage’s DNA when it is integrated into the bacterial genome during the lysogenic cycle.
How do bacteriophages release from the bacterial cell?
- Bacteriophages are released when the host bacterial cell undergoes lysis due to the accumulation of viral particles.
Can bacteriophages be engineered for therapeutic purposes?
- Yes, bacteriophages can be engineered to target specific bacteria, making them potential tools for therapy against bacterial infections.
What are the environmental implications of using bacteriophages?
- Using bacteriophages can reduce the use of antibiotics and decrease antibiotic resistance, but their impact on microbial ecosystems needs careful assessment.
- Using bacteriophages can reduce the use of antibiotics and decrease antibiotic resistance, but their impact on microbial ecosystems needs careful assessment.
Cambridge IGCSE 2024 Biology (0610) Chapter 1-10
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