Question

Distinguish between temperate and virulent bacteriophages.

Short answer

Answer: The main differences between temperate and virulent bacteriophages are: 1. Life Cycles: Temperate bacteriophages have two alternative life cycles (lysogenic and lytic), while virulent bacteriophages have only the lytic cycle. 2. Host Cell Interaction: Temperate bacteriophages can integrate their DNA into the host's bacterial chromosome as a prophage during the lysogenic cycle, but virulent bacteriophages do not. 3. Host Cell Outcomes: Temperate bacteriophages can exist within host cells without damaging them during the lysogenic cycle, while virulent bacteriophages solely focus on replicating and producing new phage particles at the expense of their host cell, leading to cell lysis.

Step-by-step solution

Definition of Bacteriophages

Bacteriophages, or phages, are viruses that infect and replicate within bacterial cells. They can be classified into two main types based on their life cycles and interactions with host cells, which are temperate bacteriophages and virulent bacteriophages.

Temperate Bacteriophages

Temperate bacteriophages have a life cycle with two alternative pathways: the lysogenic cycle and the lytic cycle. In the lysogenic cycle, the phage DNA integrates into the host's bacterial chromosome, forming a prophage. The prophage is replicated along with the bacterial chromosome without causing harm to the host cell. The bacteria containing the prophage are referred to as lysogenic bacteria. Under certain stress conditions, the prophage can be induced to excise itself from the bacterial chromosome and switch to the lytic cycle. In the lytic cycle, the phage replicates inside the host cell, creating new phage particles. Eventually, the host cell is lysed, releasing the new phages to infect other bacterial cells. The choice of life cycle depends on various factors, including the host's bacterial defense mechanisms and environmental conditions.

Virulent Bacteriophages

Virulent bacteriophages have only one life cycle, which is the lytic cycle. Once they infect a bacterial cell, they immediately begin replicating and assembling new phage particles. The host cell is eventually lysed, releasing the new phages to infect additional bacterial cells. Virulent bacteriophages do not integrate their genome into the host cell's chromosome, nor do they have a lysogenic phase in their life cycle.

Distinguishing between Temperate and Virulent Bacteriophages

To distinguish between temperate and virulent bacteriophages, one can focus on their life cycles, interactions with host cells, and potential outcomes for the host cell: 1. Life Cycles: Temperate bacteriophages have two alternative life cycles (lysogenic and lytic), while virulent bacteriophages have only the lytic cycle. 2. Host Cell Interaction: Temperate bacteriophages can integrate their DNA into the host's bacterial chromosome as a prophage during the lysogenic cycle, but virulent bacteriophages do not. 3. Host Cell Outcomes: Temperate bacteriophages can exist within host cells without damaging them during the lysogenic cycle, while virulent bacteriophages solely focus on replicating and producing new phage particles at the expense of their host cell, leading to cell lysis. By understanding their life cycles, host interactions, and outcomes for host cells, we can clearly distinguish between temperate and virulent bacteriophages.