Lysogeny , or the lysogenic cycle , is one of two viral reproduction cycles (the lytic cycle being the other). Lysogeny is characterized by the integration of nucleic acid bacteriophase into the genome or host bacterial formation of a circular replica in a bacterial cytoplasm. In this condition bacteria continue to live and reproduce normally. The genetic material of bacteriophage, called profage, can be transmitted to a child's cell at each subsequent cell division, and subsequent events (such as UV radiation or the presence of certain chemicals) may release it, causing a new phage proliferation through the lytic cycle. The lysogenic cycle may also occur in eukaryotes, although the method of incorporation of DNA is not fully understood.
The difference between the lysogenic and lytic cycles is that, in the lysogenic cycle, the spread of viral DNA takes place through ordinary prokaryotic reproduction, whereas the lytic cycle is faster because it produces many copies of the virus that are made very quickly and the cell is destroyed. One of the major differences between the lytic cycle and the lysogenic cycle is that the lysogenic cycle does not lyse the host cell directly. Phases that replicate only through the lytic cycle are known as evil phages while the replicating phage using lytic and lisogenic cycles is known as the moderate freak.
In the lysogenic cycle, the DNA of the phagula first integrates into the bacterial chromosome to produce a prediction. When the bacteria reproduce, the prophecies are also copied and present in each child cell. The child's cells can continue to replicate with a prophetic gift or a forecast can come out of the bacterial chromosome to initiate the lytic cycle.
Video Lysogenic cycle
Bacteriophages
Bacteriophages are viruses that infect and replicate in bacteria. Temperate freaks (such as lambda fage) can reproduce using lytic and lysogenic cycles. Through the lysogenic cycle, the bacteriophage genome is not expressed and is instead integrated into the bacterial genome to form forecasts. Because bacteriophage genetic information is incorporated into the bacterial genetic information as a prophecy, bacteriophages replicate passively when bacteria divide to form the child's bacterial cells. In this scenario, female bacterial cells contain prophecies and are known as lysogens. Lysogens can remain in the lysogenic cycle for several generations but can switch to the lytic cycle at any time through a process known as induction. During induction, the DNA of the profosa is cut from the bacterial genome and transcribed and translated to make the mantle protein for the virus and regulate lytic growth.
The model organism for studying lysogeny is lambda phage. The integration of prophage, lysogeny maintenance, induction, and excision control of phage genome in induction are described in detail in the phage lambda article.
Fitness sacrifice for bacteria
Bacteriophages are parasites because they infect host, use bacteria machine to replicate, and finally lyse bacteria. Freaks that emit temperature can cause advantages and disadvantages for its host through the lysogenic cycle. During the lysogenic cycle, viral genomes are included as a prophase and repressor prevents viral replication. Nonetheless, moderate fagulation can avoid repression to replicate, produce viral particles, and lyse bacteria. Ongoing freak suppression will be detrimental to bacteria. On the other hand, prophethood can transfer genes that increase virulence and host resistance to the immune system. Also, the repressors generated by predictions that prevent proase genes are otherwise immune to host bacteria from lytic infections by associated viruses.
Lysogenic conversion
In some interactions between lysogenic and bacterial phages, lethogenic conversion may occur, which can also be called phage conversion. This is when a phage is being induced to change the phenotype of an infected bacteria that is not part of the normal phage cycle. Changes often involve the cell's external membrane by making it resistant to other phages or even by increasing the pathogenic ability of bacteria to the host. In this way, temperate bacteriophages also play a role in the spread of virulence factors, such as exotoxins and exoenzymes, among bacteria. This change then resides in the genome of the infected bacteria and is copied and passed down to the child's cells.
Bacteria survive
Lysogenic conversion has been shown to allow the formation of biofilms in Bacillus anthracis. The recurrent strains of B. anthracis of all phages can not form biofilms, which is a bacterial community attached to the surface that allows bacteria to more easily access nutrients and withstand environmental stress. In addition to biofilm formation at B. anthracis, the lysogenic conversion of Bacillus subtilis , Bacillus thuringiensis , and Bacillus cereus has shown increased rate or sporulation rate. Sporulation produces endospores, which are metabolic dorman forms of bacteria that are highly resistant to temperature, ionizing radiation, drying, antibiotics, and disinfectants.
Virulence of bacteria
Non-virulent bacteria have also been shown to turn into highly virulent pathogens through lysogenic conversion by virulence factors carried on lysogenic forecasts. The virulence genes brought in prophecy as separate autonomous genetic elements, known as fools, benefit the bacteria that indirectly benefit the virus by increasing the viability of lysogen.
Example:
- Corynebacterium diphtheriae produces diphtheria toxin only when it is infected by phage? In this case, the gene that encodes the toxin is carried by the phage, not the bacteria.
- Vibrio cholerae is a non-toxic strain that can be toxic, producing cholera toxin, when infected with CTX phage.
- Shigella dysenteriae , which results in dysentery having toxins falling into two major groups, Stx1 and Stx2, whose genes are considered part of the lambdoid forecast genome.
- Streptococcus pyogenes , producing pyogenic exotoxins, obtained by lysogenic conversion, which causes fever and red-red rash, Scarlet Fever.
- Certain strains Clostridium botulinum , which causes botulism, express botulinum toxin from the gene-trandisi.
Prevent lisogenic induction
Strategies to combat certain bacterial infections by blocking induction (transition from lysogenic to lytic cycles) by eliminating induction agent in vivo have been proposed. Reactive oxygen species (ROS), such as hydrogen peroxide, are strong oxidizers that can break down into free radicals and cause DNA damage to bacteria, leading to prophetic induction. One potential strategy to combat induction of skipper is through the use of glutathione, a powerful antioxidant that can eliminate free radical intermediates. Another approach may lead to overexpression of CI repressors because the induction of prophase occurs only when the concentration of CI repressors is too low.
Maps Lysogenic cycle
References
Source of the article : Wikipedia
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