Temperateness (virology)

Temperateness (Virology)

Electron micrograph of a bacteriophage, which can exhibit temperate behavior.

In the field of virology, temperateness refers to a specific type of interaction between a bacteriophage and its bacterial host. A temperate phage is capable of entering a lysogenic cycle, where it integrates its genetic material into the host's genome and replicates along with it, rather than immediately lysing the host cell. This behavior contrasts with that of a virulent phage, which only follows the lytic cycle, leading to the destruction of the host cell.

Lysogenic Cycle

In the lysogenic cycle, the temperate phage's DNA is incorporated into the host bacterium's chromosome, becoming a prophage. This integration is facilitated by specific enzymes that allow the phage DNA to recombine with the bacterial DNA. Once integrated, the prophage is passively replicated along with the host cell's DNA during cell division. This allows the phage to persist in the host population without causing immediate harm.

The lysogenic cycle can be advantageous for the phage, as it allows the viral genome to be maintained in a stable environment, potentially for many generations. Environmental factors, such as UV light or certain chemicals, can trigger the prophage to excise itself from the host genome and enter the lytic cycle, leading to the production of new phage particles and the eventual lysis of the host cell.

Lytic Cycle

The lytic cycle is the alternative pathway that a temperate phage can follow. In this cycle, the phage takes over the host cell's machinery to produce new phage particles. This process involves the degradation of the host DNA, replication of the phage genome, and assembly of new phage particles. Eventually, the host cell is lysed, releasing the newly formed phages to infect other cells.

Advantages of Temperateness

Temperateness provides several evolutionary advantages to phages:

• Survival in Host Populations: By integrating into the host genome, temperate phages can persist in host populations even when conditions are not favorable for lytic replication.
• Genetic Exchange: The lysogenic cycle allows for horizontal gene transfer between bacteria, as prophages can carry genes from one host to another, contributing to genetic diversity and evolution.
• Adaptation to Environmental Changes: The ability to switch between lysogenic and lytic cycles allows temperate phages to adapt to changing environmental conditions, optimizing their survival and propagation.

Related Pages

• Bacteriophage
• Lysogeny
• Lytic cycle
• Prophage
• Horizontal gene transfer