Know What is the Lysogenic Cycle: Concept and Stages

In life, we are not always healthy. There are times when you get sick and need one or two medicines as well as adequate rest. The causes are various, such as bacteria, viruses, and so on. Some viruses that settle in the human body require special and intensive treatment.

Some others just need enough rest and simple care. Viruses in the human body develop in several ways, such as the lytic cycle, lysogenic cycle, and so on.

In this paper will be discussed in more detail about the lysogenic cycle. Sinaumed’s can listen as well as get book recommendations to help study biology.

Virus Concept and Characteristics

Viruses are the smallest organisms in the world. It can infect living things such as humans, plants, animals, fungi and bacteria. Viral infections can cause both mild and severe disease in humans.

In the book Dunia: Science 3A for Grade 3 SD by Drs. H. Oanut, et al, viruses are living things that are not included in the group of animals or plants. It can cause various diseases in humans, animals and plants.

A virus can also be defined as an organism capable of multiplying or spreading itself with the mission of infecting other organisms. Then, it will have an impact on the lives of other organisms. The organism will potentially experience a disease.

It lives and reproduces itself by riding on other organisms. If the virus enters the host cell. It then inserts some kind of genetic material into the host cell and takes over the function of the host cell.

To better understand viruses, Sinaumed’s can listen to some of the characteristics of viruses which are summarized from the page. Here are the details.

  • Have only RNA or DNA genetic material.
  • Do not have cells or are acellular.
  • Smaller than bacteria.
  • Has a variety of shapes.
  • Can only be seen using an electron microscope.
  • Can be crystallized.
  • Requires nucleic acid to reproduce.
  • Has no cytoplasm.
  • No metabolic activity.

Virus Structure and Grouping

The virus consists of several parts as follows.

1. Head

The head of the virus contains DNA or RNA which is the genetic material for life. The head of the virus contains nucleic acid. For viruses with a bacteriophage structure, the nucleic acid is DNA. Its function is to control the virus.

2. Capsid

The capsid is the part of the viral head which is covered by protein. It is composed of protein units called capsomeres. Its main function is to provide shape while protecting the virus from environmental conditions that are detrimental to the virus.

3. Contents of the Body or Virion

The body contents of viruses are genetic material in the form of DNA or RNA nucleic acids. The type of nucleic acid in the virion will influence the body shape of the virus. Virions can be cuboidal, spherical, or polyhedral-like RNA that viruses usually have.

4. Tail

Viruses have tails which serve as a place to attach themselves to host cells or other cells of the organisms they host. The tail consists of the tail sheath, tail fibers and base plate. At each end of the tail fiber there is a receptor that functions as a stimulus receiver.

Viruses come in many forms and variations. However, whatever the form and variation, it can still infect humans and other living things. Launching from the page, the following is a grouping of viruses based on their shape.

  • Helix or spiral staircase shape. An example of a helix-shaped virus is the tobacco mosaic virus.
  • Icosahedral, or nearly circular shape.
  • Envelope , which is a virus surrounded by a lipid membrane. It includes viruses with this envelope, namely HIV and influenza viruses.
  • Other forms, for example viruses with a combination of helices and icosahedrals.
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Difference between Virus and Bacteria      

Viruses and bacteria have a number of differences as follows.

1. Size

Viruses have sizes ranging from 20-300 nm. Body size is smaller than bacteria which are generally larger than 1,000 nm. Not only that, viruses can only be seen with an electron microscope (ME). Meanwhile, bacteria can be seen with a light microscope.

2. Chemical composition

Bacteria have a chemical composition consisting of RNA, DNA, and proteins. Meanwhile, the chemical composition of the virus consists of a single core in the form of only one RNA or DNA molecule. Generally, in bacteria there are enzymes for exchange or metabolism while viruses do not have them.

3. Living Place

Bacteria are organisms that can live in living or dead cells or tissues. Meanwhile, viruses are only able to live in living cells or tissues (hosts) such as animals or humans.

Bacteria can live inside cells (intracellular) or outside cells (extracellular) however, viruses can only live intracellularly.

4. Mutation

Bacteria do not have the power of mutation or what is commonly referred to as the power to change the nature of their antigens. On the other hand, the virus has the ability to mutate spontaneously. For example when irradiated or treated with certain chemicals.

5. How to Breed

Bacteria reproduce by splitting pairs ( binary fission ). Meanwhile, viruses reproduce through a series of stages, namely infection, viroexis, pinocytosis, and the eclipse phase. If the host cell dies, the virus will die too. Meanwhile, bacteria are able to live as saprophytes even though the host cell has died.

Lysogenic Cycle Concept

The lysogenic cycle is a viral reproduction cycle that involves the integration of viral nucleic acid into the host cell genome to create prophage . The working system of this virus does not destroy cells in the lysogenic cycle.

It will continue to live and reproduce normally. Meanwhile, the genetic material in the prophage will be transmitted to the origin of the daughter bacteria.

In summary, the lysogenic cycle has almost the same stages as the lytic cycle. The difference lies in the way it inserts itself. it does not destroy the host cell, but integrates with the host DNA. If the host cell divides the nucleic acid, the virus will also divide and insert into the host’s DNA.

The lysogenic cycle was discovered by Andre Lwoff in 1950. The virus that uses the lysogenic cycle is the HIV virus which causes Acquired Immunodeficiency Syndrome (AIDS).

Stages of the Lysogenic Cycle

The lysogenic cycle consists of several stages as follows.

1. Adsorption and Penetration

In the adsorption and penetration stages, the virus will attach to the surface of the host cell with a specific protein receptor. Then it will destroy the cell membrane with the enzyme lysozyme.

The virus will penetrate the host cell. You do this by injecting the genetic material contained in the nucleic acid into the cell.

2. Merger Stage

Viral DNA enters the bacterial body and a merger occurs between the bacterial DNA and the viral DNA. The DNA is in the form of a necklace that has no end. Then, the viral DNA will insert between the disconnected bacterial DNA. Then, a complete DNA sequence is formed that has been infected or inserted by viral DNA.

3. Cleavage Stage

Viral DNA that has been connected to bacterial DNA makes viral DNA unable to move. This state is called prophage. When the bacterial DNA replicates directly in the cell, the prophage will also replicate. This is because viral DNA combines with bacterial DNA.

Likewise, when a bacterial cell undergoes division. Directly, the two daughter cells of the bacteria that contain the prophage also undergo division. Thus, the number of prophage equals the number of bacteria in the host cell.

4. Synthesis Stage

Under certain environmental conditions, prophage becomes active. Profags can separate themselves from the bacterial DNA and damage the bacterial DNA. Then, replacing the role of bacterial DNA with viral DNA for protein synthesis which functions as a capsid for new viruses and DNA replication.

5. Assembly Stage

At the assembly stage, the viral capsids are intact as the viral envelope. After the viral capsid is intact, it will be filled with replicated DNA. Then, created new viruses.

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6. Lysis Stage

In the lytic stage, the bacterial wall will break and the virus will scatter out. Then it will attack other bacteria.

The Concept and Stages of the Lytic Cycle        

The lytic cycle is a viral reproduction process that is carried out by multiplying or replicating within the host’s body. Then, destroying the host’s body. Viruses that reproduce by the lytic cycle will penetrate the host.

When in the host’s body, the virus will multiply itself. Then, exit the host. After that, the host cell will experience lysis or rupture.

The lytic cycle occurs after going through the following stages.

1. Adsorption

Adsorption is the attachment stage of the virus particle or virion to a suitable host cell.

2. Penetration

Penetration is the stage of injection of viral nucleic acid into the host cell. The virus will perforate the host cell plasma membrane (and cell wall, if present) using enzymes such as lysozyme on bacteriophages.

3. Replication

At the replication stage, duplication occurs or the virus reproduces itself by using the nucleic acids in its body.

4. Assembly

At the assembly stage, the viruses will form their bodies. At this stage, the capsid that has been formed in the synthesis stage will begin to be filled with replicated nucleic acids so that it becomes a complete virus.

5. Lysis

During the lysis stage, mature virus particles are released.


Difference between Lysogenic Cycle and Lytic Cycle

The lytic and lysogenic cycles have several differences, apart from how they ride on the host. Here are some of the differences reported from the page.

  • Viral DNA is not integrated in the lytic cycle, while in the lysogenic cycle integration of viral DNA into the host cell DNA occurs.
  • The host DNA in the lytic cycle is hydrolyzed, while the host DNA in the lysogenic cycle is not hydrolyzed.
  • The difference between the lytic and lysogenic cycles can also be seen from the absence of a prophage stage in the lytic cycle, while the lysogenic cycle does.
  • Viral DNA replication in the lytic cycle occurs independently, while in lysogenic it occurs with the host DNA.
  • The lytic cycle occurs in a short time, while the lysogenic cycle can take a longer time.
  • The cellular mechanisms are taken over by the viral genome in the lytic cycle, while the host cell’s cellular mechanisms are disrupted by the viral genome in the lysogenic cycle.

How to Prevent and Overcome Virus Infections

We as humans can prevent contracting certain viruses as well as overcome if the virus has already infected the body. Here are some ways to prevent and deal with virus infections which are summarized from the page.

1. Maximizing the Immune System

The body will respond to a virus attack by being detected first by the immune system. Then the immune system will help the body to survive and recover. This resistance process is called RNA interference or DNA interference. The goal is to break down the genetic material of the virus.

When this process occurs, the immune system will produce special antibodies that are able to bind to viruses. So, hopefully, the virus is not contagious. The T cells from the body will also try to destroy the virus.

However, various types of viruses can avoid this resistance, such as HIV and neurotropic viruses. Neurotropic viruses are viruses that attack nerve cells and affect the structure of the central nervous system. Some diseases caused by neurotropic viruses are rabies, polio, mumps, and measles.

2. Vaccines

Vaccines are the most effective and easy way to prevent viral infections. Vaccines can be done by the following methods.

  • Viral proteins are called antigens. The antigen stimulates the body to form antibodies that will fight future infections with the same virus.
  • Live attenuated virus is like immunization for polio.

3. Take Antiviral Medication

If the infection is caused by bacteria, it can be treated with antibiotics. While viral infections are treated with antiviral drugs. It works by inhibiting the virus’ ability to reproduce. Such as HIV infection, influenza, hepatitis B and C can be treated with antiviral drugs.

4. Living a Healthy Lifestyle

Lifestyle has an influence on the body. It is able to prevent viruses that attack the body. A stable body metabolism can reduce the risk of developing chronic disease or dying at a young age. Here are some steps to a healthy lifestyle that can be taken to prevent the virus.

  • Watch your food intake
  • Reduce alcohol consumption
  • Do not smoke
  • Exercise regularly
  • Do activities you like