Given the name I have chosen for this blog, the first entry could only be about viruses!
What are viruses?
Viruses are very special creatures, and my biology teacher in High school introduced them as “packages of information”. In fact, they are simply made of their genetic information in the form of DNA or RNA (genome), surrounded by a coating made of proteins (capsid) and sometimes by a lipidic envelope (pericapsid). Some are also equipped with specific proteins to make copies of their genetic content (replication).
Are viruses alive?
Viruses are not proper living beings since they are not able to reproduce themselves on their own. To do so they must enter a cell and use its functions to complete their replication, produce new proteins for their capsid and form new viral particles (virions) able to invade more cells of the same of other individuals to ensure their spreading. Viruses are therefore microscopic parasites that need a “host” to be alive. This phenomenon is called viral infection.
Are all viruses the same?
There are many kinds of viruses, with different shapes and dimensions, and they are classified by virologists according to their characteristics such as the route of transmission. For example, some viruses can spread in the air, others through body fluids, and others are conveyed by vectors, such as mosquitos or other insects.
There are viruses which all of us have heard about at least once, like influenza virus, the viruses that cause hepatitis (I will write a post about them) and chickenpox (varicella) virus. Some viruses infect animals, others infect plants, and others infect bacteria (bacteriophages). Some scientists have suggested the presence of viruses in the entire Universe, not only on our planet; the branch of Biology called Astrovirology has the task of discovering and study such alien viruses.
Speaking of plant viruses, it was a viral infection that allowed the production of variegated tulips, extremely sought-after during the XVII century: only infected plants gave origin to multi-coloured flowers. Did you ever imagine that?
Are all viruses harmful?
Often, but not always, a viral infection causes damage to the infected organ, characterised by the death of the cells or their transformation into cancer cells; it is the event of this damage that we call “disease”. Sometimes, however, the infection can be asymptomatic and goes unnoticed. This is the case of viruses that have coexisted for a long time with their host; when the virus and the host species coevolve, the symptoms of the infection go milder and milder (advantage for the host), allowing the infected organism to live longer contributing to the spreading of new infective particles (advantage for the virus).
However, viruses are not always the bad guys. Scientists are now able to exploit their ability to enter into the cells to our benefit. One of the most important achievements of modern biotechnology is indeed virus modification in order to use them as gene therapy vectors: in other words, they are used to transfer the corrected copy of a faulty gene to the cells of patients affected by genetic disorders. But this will be the topic of one of my future posts.
The world of the viruses is really amazing and fascinating, isn’t it?
Bibliography
Viruses and cells intertwined since the dawn of evolution. Durzyńska J.et al., Virol J. 2015, https://doi.org/10.1186/s12985-015-0400-7
Astrovirology: Viruses at Large in the Universe, Berliner A.J. et al., Astrobiology 2018, https://doi.org/10.1089/ast.2017.1649
Tulip Breaking: Past, Present, and Future, Judith A. et al. Plant Disease 2007, https://doi.org/10.1094/PDIS.2000.84.10.1052
Parasite Virulence and Parasite-Host Coevolution: A Reappraisal, Garnick E., The Journal of Parasitology 1992, https://doi.org/10.2307/3283496
Viral Vectors for Gene Transfer,Chen Y.H. et al., Curr Protoc Mouse Biol. 2018 https://doi.org/10.1002/cpmo.58
Picture from freesvg.org (Public domain)
Virus&Co. 
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