Peter Medawar, defined viruses as a fraction of nucleic acid encircled by bad news. I think he said that because of how viruses have traditionally been assumed in a negative context as agencies accountable for diseases that must be eradicated. Take a look around you. Everyone is walking with their face covered, a little sneeze plop fear in people, blowing air into birthday cakes is unhealthy and hugging loved ones seems difficult nowadays. Why is it so? Because our world has changed. The planet is occupied by entities we can not see with the naked eye. But, do you believe the world will be a better place if these entities are erased? This article discusses the basics of what viruses are, how they came about, how they infect and replicate, and their economic importance to human life.
WHAT CONSTITUTES VIRUSES?
Viruses are small fragments of DNA or RNA that are covered by a layer of protein and can only be multiplied inside the live cells of an organism. However, DNA is the genomic material that contains the genetic information used in the development of living organisms while RNA is a messenger that carries instructions from DNA for protein synthesis. Although in some Viruses, RNA carries genetic information instead of DNA.
Take note that viruses are complicated to understand the origin of their existence. Why do l say that? We all know at the basic level that viruses are not qualified to be called living organisms because they can not survive on their own. But, the DNA or RNA that make up a virus is only found in the cells of living things. Another mind-blowing thing about a virus that makes it difficult to understand is its skin (protein coating).
A protein coat is a protein surrounding the DNA or RNA of a virus. So, the protein coat conserves the nucleic acids of the virus from the external environment. And it is called a capsid.
Surprisingly, viruses lack ribosomes to synthesize proteins. And life is impossible without ribosomes to produce protein.
Ribosomes contain RNA that holds all of the instructions necessary to carry out protein synthesis in which proteins are formed from amino acids that bind together to form chains. These protein chains aid the body to carry out specific processes.
So how on earth do the entire virus particle get their structure, nucleic acids, and develop capsids? no one knows exactly since they don't leave a fossil. But, modern viruses are understood to be a mosaic of nucleic acids taken from different sources with their subordinate evolutionary paths.
THE HISTORY OF VIRUSES.
Viruses were originally recognized when certain organisms that cause disease were passed through filters meant to prevent bacteria. This experiment was observed by French chemist Louis Pasteur in 1887. Later on, it was identified by Edward Adolf Mayer, that tobacco mosaic disease could be possibly carried to plants that are healthy if they are immunized with selections of fluid from diseased plants. Adolf was not telling the exact parasites but he was convinced that it was a different bacteria. Though he didn't point out the process the disease developed, he being sure, it was known to a lot of people that his microorganism was identified as a very unique pathogen.
Alternatively, it was constantly uncontrollable to allocate a period finding viruses, a scientist was able to spot an entity that was submicroscopic on the surface of a habitation, different from bacteria and filterable that served as factors of the tobacco mosaic disease. Dmitrii Borisovich lvanovsky formed the term to clarify this pathogen before the name was adopted as "virus".
The disposition of the virus ( tobacco mosaic viruses) as a filterable virus was verified by Beijerinck, but he could not isolate the virus. so, he developed infectious living fluid that only reproduces inside living cells. His idea was unusual at that time. That is in the year 1898.
Hence, Adolf, Ivanofsky, and Beijerinck had a part in the development of a novel concept- a filterable agent tiny to be identified by the use of the microscope but causes infection by replicating in living cells of an organism.
Another group of scientists, Loeffler Friedrich and Frosch Paul clarified the early filterable agent from animals which is the mouth, foot disease virus, and Reed including his crew in Cuba recognized the human filterable virus the first time in 1898.
The virus which was poison was derived from Latin and was used interchangeably for any contagious agent at that moment and it was called a tobacco mosaic virus as well.
As time goes on, Mayer, Ivanofsky, and Beijerinck specified the term used for the agents that fit the criteria to cause diseases.
CLASSIFICATION OF VIRUSES BASED ON THEIR MORPHOLOGY.
In the past, viruses were classified based on their genetic material, the structure of their capsids, and whether they have an additional coat called the envelope. But today, The used classification technique is called the Baltimore classification which is based on their messenger RNA integration in each type of virus. However, we are looking at the types of viruses based on their shapes.
In general, there are four categories of viral shapes: filamentous, isometric (or icosahedral), enveloped, and head and tail.
Filamentous viruses: Filamentous viruses are cylindrical and lengthy in shape that affects bacteria, and several plant viruses are filamentous. For example, the tobacco mosaic virus.
Isometric viruses: Isometric viruses have roughly spherical shapes with 20 sides, each composed of equilateral triangles such as poliovirus.
Enveloped viruses: Enveloped viruses have membranes enclosing their skin[protein coat] Examples are animal viruses, such as HIV.
Head and tail viruses: Head and tail viruses mostly infect bacteria. They have a head that is identical to isometric viruses and a tail shape like filamentous viruses.
STEPS OF VIRUS INFECTION.
A general successful viral infection involves attachment, penetration, break down of the virus particle (uncoating), replication, translation, assembly, and transportation.
A virus adheres to a receptor site on the host-cell membrane through the attachment proteins in the capsid and penetrating the cell membrane. The genetic material[RNA or DNA] of the virus is uncoated from the capsid and injected into the host cell. Then the viral genes[RNA or DNA] hijack the machinery of the host cell causing it to replicate the genes of the virus and make new capsids through the production of viral proteins.
Next, the virus particles assembled into new viruses. The new viruses blast out of the host cell through the breakdown of the cell plasma membrane which destroys the host cell and goes on to infect different cells. Also, some viruses carry a part of the membrane of the host during the damage of the cell to form an envelope around the protein coat[skin].
In a nutshell, viruses have specific useful properties that can be capitalized on for valuable bases, as is apparent in both vaccination and gene therapy. But, we tend to focus only on the ones that cause humanity trouble. The recent Covid-19 pandemic is barely one in a sequel of never-ending deadly viral assaults that have confirmed viruses as unneeded entities on earth. But, we should understand that it is impossible to annihilate all viruses in the world. So, we should understand more how integral viruses are and how much we still need to learn about viruses. Don't forget to observe all the protocols that will save you from contracting viruses.
- "12.1 Viruses – Concepts of Biology – 1st Canadian Edition" Retrieved from https://opentextbc.ca/biology/chapter/12-1-viruses/
- "Virus Structure and Classification" Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7150055/
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