Lysogenic cycle

Lysogeny is characterized by integration of the bacteriophage nucleic acid into the host bacterium's genome or formation of a circular replicon in the bacterial cytoplasm.

A phage may decide to exit the chromosome and enter the lytic cycle if it is exposed to DNA-damaging agents, such as UV radiation and chemicals.

Other factors with the potential to induce temperate phage release include temperature, pH, osmotic pressure, and low nutrient concentration.

Detection methods of phages released from the lysogenic cycle include electron microscopy, DNA extraction, or propagation on sensitive strains.

If prophages become active, they can exit the bacterial chromosome and enter the lytic cycle, where they undergo DNA copying, protein synthesis, phage assembly, and lysis.

[8] During induction, prophage DNA is excised from the bacterial genome and is transcribed and translated to make coat proteins for the virus and regulate lytic growth.

In the case of genital herpes, latency is established in lumbosacral dorsal root ganglia, spinal nerve neurons.

[13] Another system, arbitrium, has recently been described for bacteriophages infecting several Bacillus species, in which the decision between lysis and lysogeny is transmitted between bacteria by a peptide factor.

Changes can often involve the external membrane of the cell by making it impervious to other phages or even by increasing the pathogenic capability of the bacteria for a host.

[16] Strains of B. anthracis cured of all phage were unable to form biofilms, which are surface-adhered bacterial communities that enable bacteria to better access nutrients and survive environmental stresses.

[16] Sporulation produces endospores, which are metabolically dormant forms of the bacteria that are highly resistant to temperature, ionizing radiation, desiccation, antibiotics, and disinfectants.

[18] Virulence genes carried within prophages as discrete autonomous genetic elements, known as morons, confer an advantage to the bacteria that indirectly benefits the virus through enhanced lysogen survival.

[18] Reactive oxygen species (ROS), such as hydrogen peroxide, are strong oxidizing agents that can decompose into free radicals and cause DNA damage to bacteria, which lead to prophage induction.

Lysogenic cycle, compared to lytic cycle
Lysogenic Cycle:1. The prokaryotic cell is shown with its DNA, in green. 2. The bacteriophage attaches and releases its DNA, shown in red, into the prokaryotic cell. 3. The phage DNA then moves through the cell to the host's DNA. 4. The phage DNA integrates itself into the host cell's DNA, creating prophage. 5. The prophage then remains dormant until the host cell divides. 6. After the host cell has divided, the phage DNA in the daughter cells activate, and the phage DNA begins to express itself. Some of the cells containing the prophage go on to create new phages which will move on to infect other cells.
Lysogenic Cycle [ 9 ]