Key Characteristics and Classification of Viruses
In the field of microbiology, Virology primarily deals with the study of viruses as well as virus-like particles. The research and observations are based on the characteristics, classifications, and the relationship of the viruses with their hosts. Viruses are unique traits that set them apart from others in the microbiology world.
You know by now that viruses multiply fast and their structure is also quite different from other microscopic particles. Viruses are microscopic parasites that cannot thrive. They are capable of latching on to host cells and getting inside them. Here we will discuss virology meaning and the principles of virology.
What is Virology?
Virology came forward as a science at the end of the 19th century. It relates to the study of microscopic agents responsible for plant and animal infectious diseases. Tobacco mosaic virus, foot and mouth disease virus, and yellow fever virus were among the first viruses discovered. Approximately 30 years later (around the year 1927) there came forward a list of about three dozen diseases that were thought to be caused by viruses.
Viruses were mainly placed together according to their visual symptoms and modes of transmission. It was the first phase of Virology. Then came the electron microscope in the late 1930s. Viruses came to be known as particles. It did not take long to recognise these particles as nucleic acid and proteins. Thus, proteins and nucleic acids were firmly established as components of animal and plant viruses.
Over time, the introduction of cultured cells for in-vitro propagation of viruses accelerated the pace of virus discovery. There arose a need to classify and name groups of viruses. Biology, genetics, and morphology, and physicochemical properties of virus components came into the scene. Around 2012, the introduction of extremely sensitive and high-sequencing technologies made dramatic changes. The world saw a multitude of novel viruses, most of them known by their genomic (hereditary) formation.
The classification of the virus according to their genome (hereditary) sequence may be in consideration as the ongoing phase of virus taxonomy or classification.
Characteristics of a Virus
As you know viruses are infectious agents with living and nonliving characteristics. A virus can infect animals, plants, and other microorganisms. Viruses that infect only bacteria are known as bacteriophages. Viruses that infect fungi are known as mycophages. And, the virus that attacks other viruses is known as virophages. Characteristics of viruses can be living as well as non - living.
The Living Characteristics of Viruses are:
They reproduce at a fast rate, only in living host cells.
They can mutate
The Non - Living Characteristics of Viruses are:
They are not cells, contain no cytoplasm or cellular organelles.
They don’t grow and divide.
New viruses are synthesized and assembled within the infected host cell.
The majority of viruses possess either DNA or RNA, not both.
Types of Virus
There are only two categories of viruses according to general composition- RNA and DNA.
RNA Virus - it is that type of virus that has RNA as its genetic material. It can be a single-stranded or double-stranded RNA. Diseases caused by the RNA virus include common cold, polio, hepatitis, influenza, measles, and SARS. Plant virus is an example of an RNA virus.
DNA Virus - It is a type of virus that has DNA as its genetic material. They depend on the DNA and replicate using the DNA polymerase. They are sometimes double-stranded. In some cases, they can be single-stranded. Most of the animal viruses, bacteriophages, cyanophages, and animal viruses are examples of DNA viruses.
Based on genetic material, and type of host, we can say that there are three types of viruses - Animal virus, Plant virus, and Bacteriophages.
Molecular Virology
Molecular virology refers to the study of viruses at the molecular level. It involves the analysis of genes and gene products. It refers to the study of the interaction with the host- human, plant or animal- cellular proteins. Teams working in the lab think about molecular testing as the trend in the future. Molecular diagnostics have become the new normal. The introduction of automated systems provides the tools necessary to report accurate and sensitive results to clinicians – it can improve patient care and outcomes by correct and fast diagnosis.
Conclusion
The principles of virology state that a virus is made up of genetic material, known as either DNA or RNA. It is essential to understand that infections are of medical and veterinary significance. Virology has become one of the most important sub-disciplines of microbiology. It has allowed researchers to discover treatments and cures for the diseases that they cause. Besides, virology is in use for pharmaceutical purposes also. Get the study materials from the Vedantu website.
FAQs on Virology: Understanding Viruses and Their Impact
1. What is virology and what does its study encompass?
Virology is the scientific discipline within microbiology that focuses on the study of viruses and virus-like agents. It covers their structure, classification, evolution, and mechanisms of infection in host cells. The field also explores how viruses cause diseases, the immune responses they trigger, and the development of techniques to isolate, culture, and use them in research and medicine.
2. Why are viruses often described as being on the borderline between living and non-living?
Viruses are considered to be on the borderline because they exhibit characteristics of both living and non-living things.
- Living characteristics: They possess genetic material (DNA or RNA) and can evolve through natural selection.
- Non-living characteristics: Outside a host cell, they are inert crystalline structures and lack their own cellular machinery for metabolism or reproduction. They are obligate intracellular parasites, meaning they can only replicate by taking over a living host cell.
3. How do viruses differ from bacteria?
Viruses and bacteria are fundamentally different. Viruses are much smaller, non-cellular entities consisting of genetic material enclosed in a protein coat called a capsid. Bacteria, on the other hand, are single-celled prokaryotic organisms with a complete cellular structure, including a cell wall, cytoplasm, and ribosomes. Unlike viruses, bacteria can reproduce independently through binary fission and are susceptible to antibiotics.
4. What is the basic structure of a typical virus?
A virus particle, or virion, has a simple structure. At its core is the genetic material, which can be either DNA or RNA, but never both. This genetic core is protected by a protein shell known as the capsid. The capsid is made of smaller protein subunits called capsomeres. Some viruses, like the influenza virus, also have an outer lipid membrane called an envelope, which is derived from the host cell membrane and may have protein spikes for attachment.
5. What is the difference between a DNA virus and an RNA virus, with examples?
The primary difference lies in their genetic material. DNA viruses, such as Herpesvirus and Poxvirus, contain Deoxyribonucleic Acid. They often replicate their DNA in the host cell's nucleus. RNA viruses, like the Influenza virus, Retroviruses (e.g., HIV), and Coronaviruses, contain Ribonucleic Acid. RNA viruses typically replicate in the cytoplasm and are known for higher mutation rates as RNA replication is more error-prone.
6. How does a virus replicate using a host cell?
A virus replicates by hijacking the host cell's machinery. The process generally involves these steps:
- Attachment: The virus attaches to a specific receptor on the host cell surface.
- Penetration: The virus or its genetic material enters the host cell.
- Synthesis: The viral genetic material takes control of the cell's metabolic machinery to produce viral proteins and replicate its own genome.
- Assembly: New viral particles are assembled from the newly synthesised components.
- Release: The new virions are released from the host cell, often by causing it to burst (lysis), which kills the cell.
7. What are some examples of important viral diseases in humans?
Viruses are responsible for a wide range of human diseases, from mild to severe. Common examples include the common cold (caused by Rhinoviruses), influenza (Influenza virus), chickenpox (Varicella-zoster virus), measles (Morbillivirus), and poliomyelitis (Poliovirus). More severe diseases include AIDS (caused by the Human Immunodeficiency Virus or HIV) and COVID-19 (caused by SARS-CoV-2).
8. What is the importance of virology in the field of medicine?
Virology is crucial to modern medicine for several reasons. It is essential for the diagnosis of viral infections through serological tests and molecular techniques. The most significant application is in the development of vaccines, which prevent viral diseases by stimulating the immune system. Furthermore, virology aids in creating antiviral drugs that target specific stages of the viral life cycle. Viruses are also studied for their potential use in gene therapy and as agents to fight cancer (oncolytic viruses).
9. What are bacteriophages and why are they significant?
Bacteriophages, or phages, are viruses that specifically infect and replicate within bacteria. They are among the most common and diverse entities in the biosphere. Their significance lies in their role in controlling bacterial populations in natural ecosystems. In medicine, they are being explored as an alternative to antibiotics for treating bacterial infections, a concept known as phage therapy, which is becoming increasingly important with the rise of antibiotic-resistant bacteria.
