Almost everyone has contracted the virus, maybe you’re also one of them? Simply put, viruses are the cause and contagion of diseases, such as smallpox and influenza. Surely you have experienced it, right?
In addition to causing various diseases, the virus can also be used to fight diseases caused by the virus itself or known as vaccines. Well, what about the process of virus reproduction?
Broadly speaking, the virus spreads through two cycles, namely the lytic cycle and the lysogenic cycle. In this article, you can better understand one of the virus spread cycles. Let’s take a good look at how the virus is transmitted through the lytic cycle.
Lytic Cycle Definition
The lytic cycle is a replication of the genome of the virus, culminating in death in the host cell where the virus lives. When the walls of the host cell rupture, new viruses that form inside will come out. Then the virus will search for a new host cell and infect it.
Viruses that can only replicate the genome with this cycle are known by the name of virulent virus or bacteriophage virus. The lytic cycle begins when the tail of the virulent virus lodges on the outer surface of the host cell.
This cycle is considered the primary means of reproduction of the virus as it concerns the destruction of its host cell.
The reproduction through this lytic cycle begins with the sticking of the virus to the bacteria. Where, viral enzymes dissolve the walls of bacterial cells so that holes form and through the hole, the virus inserts its DNA into the bacteria.
Viral DNA that has entered into bacteria takes over the task of bacterial DNA by destroying the DNA of those bacteria. After that, in the body bacteria synthesized DNA, wrapping proteins, and other parts of the viral body (one bacterial cell is enough to form 300 new viruses).
Once a new virus is formed, the cell walls of the bacteria are destroyed or called lysis, so that the newly formed virus will come out and infect other bacteria.
Lytic cycle steps
The lytic cycle is the cycle of reproduction or replication of the viral genome, which will ultimately lead to death of the host cell where the virus lives. Viruses can only replicate in this cycle or in other words called virulent viruses. The lytic cycle consists of the following five stages:
Adsorption (Attachment)
The adsorption stage occurs when the tail end of a virus or commonly called a receptor attaches to the wall of the host cell. Once successfully attached to the host cell, the virus will secrete lysozyme enzymes or destroying enzymes. The function of such enzymes is to form holes in the walls of the host cells.
Penetration
Penetration is the process of inserting the genetic material of the virus into the cytoplasm of the host cell. There are several stages that occur, namely:
- The tail casing of the virus contracts and the tail tries to penetrate into the cell membrane through the cell wall (in bacteria). In some types of viruses such as Bacteriophage T4, they can produce a lysozyme enzyme that can weaken the cell walls of bacteria to be easily penetrated.
- Genetic material located inside the viral capsid is flowed into the cytoplasm of the host cell through the tail (injection).
- The empty capsid will remain outside the cell.
Some types of viruses do not have the above mechanisms, because they do not have a contractile sheath (tail part) that serves to drain their genetic material. Therefore, to penetrate, the virus enters the bacterial cell / host cell through the mechanism of endocytosis. Viral capsids composed of proteins fuse with the cytoplasmic membrane and can be destroyed so as to release the genetic material of the virus.
Replication (Biosynthesis)
After being injected into the host cell, DNA from the virus is about to disable the DNA of the host cell and then take over the work of the host cell, then use the cell to obtain energy in the wake of the ATP in carrying out its reproduction process.
DNA from the virus, wanting to make the host cell a location for the formation of a new virus, then DNA to nurture the virus into producing proteins and replicating the DNA of the virus into a new virus that is being created.
The protein molecules (DNA) that have been formed are then covered by capsids, capsids are made from host cell proteins and serve to provide the body of the virus.
Maturation Stage
After going through the third stage, the next stage is the assembly of the body of viruses that are still separated, such as the head, tail, and tail fibers, into a complete virus. In addition, intact capsids formed are also then filled by DNA / RNA so that the reproduction process successfully creates a new virus. In this phase, the resulting virus can reach 100-200 pieces.
Lysis
The lysis stage occurs when the viruses created in the cell have matured. Hundreds of viruses will then gather on cell membranes and inject lysozyme enzymes that destroy cell membranes and provide a way out for new viruses. Cells that membranes are destroyed will eventually die and viruses that are free will invade other cells and the cycle will recur.
Source:
- Image: University of Barcelona, CC BY 3.0 https://creativecommons.org/licenses/by/3.0, via Wikimedia Commons.
- Video: JohnART
