How does Cro protein expressed by lambda phage kill its host?

Question

I read that the DNA segment of lambda phage integrated in host DNA could switch between lysogenic state where cI represses the expression of *Cro* and lytic state where *Cro* expression takes over and self produces more. 1. But how exactly does the high production of *Cro* kill its host? 2. The virus has a DNA segment shielded with a protein coat. While entering host it gets attached to host membrane and releases DNA inside without damaging host. Then how does host get killed when virus goes outside it which happens during lytic phase and doesn't happen when it got inside?3. And if the virus has to go outside host, it needs protein coating. How is that produced? Is it produced only during lytic phase or also during lysogenic phase?

Answer 1

1 and 2: You're right that Cro production causes the virus to enter the lytic phase and produce additional virus. New viral particles are released by lysis of the cell which can kill the host over time if the reproduced virus continues infecting and lysing other cells in the body. Enough virus to cause a significant amount cell death would prevent essential organs from functioning. The cell is only lysed after reproduction, so there is no present danger to the host if the virus enters the cell and becomes lysogenic since there would be no lysing and no viral production.

3. Production of Cro activates production of viral proteins, some of which make up the capsid or protein coating that the virus uses to protect its DNA. Protein production is repressed during the lysogenic phase, so there is no capsid production during the lysogenic phase, only when the virus is lytic.

Watch the below video if you need more help with lambda phage, or feel free to ask me more questions!

Lambda Bacteriophage- Lytic vs Lysogenic Decision... Explained!