The Lytic Cycle of the T-Even Bacteriophage
The T-Even Bacteriophage is a virus that infects the bacterium E.coli. It is made up of a Capsid which contains the viral nucleic acid. The capsid is compose of small protein components known as capsomeres. Attached to the Capsid is the tail. The tail is made up of the sheath, tail fibers,breastplate, and the pin. The tail fibers are used to attach the virus to the outsid of the bacterial cell wall by attaching to specific receptors ont the bacteriums surface. The virus then injects its DNA into the bacterium. There are two specific viral cycles that can now occur; either a lytic cycle or a lysogenic cycle. This article will focus only on the lytic cycle.
Step 1: Attachment
The Phage encounters the bacterium and attaches itself. The virus uses its tail fibers which interact with specific receptors on the surface of the bacterium E.coli. These interactions although weak are strong enough to hold the virus firmly to the surface of the bacterium. It is important to remember that these interactions are very specific and will only allow the virus to attach to its specific host, in this case E.coli.
Step 2: Penetration
Immediately after the virus attaches to the bacterium it squats down and injects its DNA into the bacterium. The DNA is the only component injected into the bacterium, the protein coat remains on the outside of the Bacterium.
Step 3: Biosynthesis
Once the Viral DNA is injected into the Bacterium it travels into the cytoplasm and takes over the cells functions. The Bacterial DNA is chopped up and degraded. The viral DNA is transcribed in the cytoplasm producing viral mRNA. Numerous copis of the viral DNA are created. Then the mRNA is then transcribed producing various components of the virus, such as tail fibers, capsids, and nucleic acids. No complete virions are present at this stage.
Stage 4: Maturation
It is a this stage where the viral components are assembled. At this stage fully complete infectious Virions are now present in the cytoplasm of the bacterium. This causes the bacterium to swell.
Step 5: Release
In the last stage of the lytic cycle the bacterium swells and lyses. This releases thousands of new fully infectious virions. These virions then go and infect other bacteria.