19.2-1CC - Campbell Biology

Question

Compare the effect on the host cell of a lytic (virulent) phage and a lysogenic (temperate) phage.

Step-by-Step Solution

Answer

Lytic phage causes the lysis of the host cell. The lysogenic phage can either cause lysis of the host cell or integrate into the host cell's chromosome and can later initiate a lytic cell.

Step 1: Lytic cycle

Phages replicate by two mechanisms: lytic and lysogenic cycle. The replicative cycle that causes the death of the host cell is called the lytic cycle. In this cycle, the virus lyses the host bacterial cell and releases the progenies produced in the bacteria.

 

The progenies further infect other bacterial cells and cause lysis of the host cell. The phages that replicate through the lytic cycle are called lytic or virulent phages.

Step 2: Lysogenic cycle

Some phages integrate into the genome of the host cell. The integrated phage genome replicates along with the replication of the host chromosome without affecting the cell. This type of replicative cell is called the lysogenic cycle. 

                             

This is because the phages coexist with the host cell in the state of lysogeny. However, these phages can initiate a lytic cell in cases where they exit the host cell. The phages that can replicate through both lytic and lysogenic cycles are called lysogenic or temperate phages.

Step 3: Comparison of the effect of the two phages on the host cell

Lytic phages cause the death of the bacterial host cell. On the other hand, the lysogenic phages integrate into the bacterial chromosome and remain in the state of lysogeny. However, these can also cause the death of the host cell if they escape the host cell and infect another host cell.

 

Thus, lytic and lysogenic phages can have a similar or different effect on the host cell.