BacteriophageBacteriophages are viruses that infect bacteria. A bacteriophage can have a protein "tail" attached to the capsid (protein coat that envelopes the genetic material), which is used to infect the host bacteria.
VirusesScientists have long sought to uncover the structure and function of viruses. Viruses are unique -- they have been classified as both living and nonliving at various points in the history of biology.
A virus particle, also known as a virion, is essentially a nucleic acid (DNA or RNA) enclosed in a protein shell or coat. Viruses are extremely small, approximately 15 - 25 nanometers in diameter.
Virus ReplicationViruses are intracellular obligate parasites, which means that they cannot reproduce or express their genes without the help of a living cell. Once a virus has infected a cell, it will use the cell's ribosomes, enzymes, and much of the cellular machinery to reproduce. Viral replication produces many progeny that leave the host cell to infect other cells.
Bacteriophage Life Cycle
A bacteriophage reproduces by one of two types of life cycles. These cycles are the lysogenic life cycle and the lytic life cycle. In the lysogenic cycle, bacteriophages reproduce without killing the host. Genetic recombination occurs between the viral DNA and the bacterial genome as the viral DNA is inserted into the bacterial chromosome. In the lytic life cycle, the virus breaks open or lyses the host cell. This results in the death of the host.
Bacteriophage Life Cycle Animation
Below are animations of the lytic life cycle of a bacteriophage.
The bacteriophage attaches to the cell wall of a bacterium.
The bacteriophage injects its genome into the bacterium.
This animation shows the replication of the viral genome.
Bacteriophages are released by lysis.
Summary of the entire lytic life cycle of a bacteriophage.