As far as living things are concerned, it does not generate any discussion indicating that an animal or a plant is. The same goes for fungi, algae and bacteria. But when it comes to viruses things change. And it is that these infectious agents are breaking the rules.
First, they are not cells, but simple protein structures, but inside they contain genetic material. Second, their only way to reproduce is through cell infection, to use their tools for that purpose. And third, they don’t need any energy because they don’t need maintenance.
Apart from the discussion to consider them as living beings or not, there is a variety both in their content and in their structures, which made it possible to identify different types of viruses. The importance of knowing them better is linked to their role as a cause of disease in living beings, some more serious than others. Better knowledge makes it possible to prevent and treat them.
Basic structure of a virus
Viruses are distinguished above all by their very simple composition. It is a protein structure, more or less complex depending on the class, which aims to protect the genetic material it carries, While acting as a vehicle for it.
The main structure of all viruses is the capsid. Formed by a set of protein units called capsomersWhen inside, it stores the genetic content changes to say-nucleocapsid. The shape of this coin is one of the criteria for identifying types of viruses.
The nucleocapsid may exhibit icosahedral symmetry, Which is observed as a spherical shape; helical symmetry, which is rod-shaped or tubular; and of complex symmetry, apart from the nucleocapsid, it has attached a protein structure which is referred to as a whole as a tail, which acts as a support to facilitate the insertion of the contents into a host.
to wrap up
However, some viruses can have a second layer, called an envelope, made up of lipids. Their presence or absence is another criterion used to classify them.
Types of viruses according to their genetic material
Unlike cells, the genetic content of these infectious agents is very varied in classes and configurations, so it is a good point to use in taxonomy. Widely, there are two main types of viruses: Those that contain DNA as genetic material and those that store their information as RNA.
Types of DNA viruses they have a small chain of nucleic acids which can be single-stranded or double-stranded, that is to say in chain or in two. In addition, it can be circular or linear, it all depends on the virus we are talking about. These are the most common viruses. For example, the cause of herpes (Herpesviridae) has genetic content that comes in the form of linear double stranded DNA.
As you can imagine, the only difference between RNA viruses and others is the nucleic acids. The same thing happens: it can be made up of one or two chains, and be linear or circular. A well-known example is the retrovirus family (Retroviridae), among the diseases that can cause this AIDS. In this case, it presents its genetic material as linear single-stranded RNA.
Depending on what they infect
Not all types of viruses have affinity for the same organisms or cells. In other words, some viruses only affect animals and not plants. Thanks to this, it can be used as a criterion for its classification. In this case it focuses on who your guest is, there are three groups:
- Animal viruses.
- Plant viruses.
- bacteriophage viruses (They attack bacteria).
The case of coronaviruses
recently the term “coronavirus” became known worldwide as a result of the global pandemic caused by one of the viral species belonging to this category. It is the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which produces the disease called COVID-19, pneumonia with a relatively high death rate in humans. This pathogen variant was discovered in the Chinese city of Wuhan, but from this point of origin it mutated several times.
But beyond this case, coronaviruses are long-known types of viruses and in the taxonomy used to classify these biological entities are in the Coronaviridae family, so they are considered a subfamily.
One of the characteristics of these species is that are RNA viruses with a longer genome, And by the protuberances of their rounded surface, which make that seen under the microscope, they seem to take a crown at the ends. On the other hand, most species of coronavirus do not pose a significant danger to most people.
How do they work?
I couldn’t end this article without explaining how viruses work generically. Viron (mature form of virus), locates a host cell, successfully introducing its genetic content inside. This material is inserted into the DNA of the nucleus, so that the cell can transcribe its information and translate it into proteins which form the capsid and others. It is also possible to replicate the genes of the virus, thus introducing it into new capsids and forming new viruses which leave the infected cell.
This is a generic way of talking about the life cycle of viruses; there are a multitude of variables. Examples cited as retroviruses must first transcribe their RNA content into DNA and make the complementary strand before they can be inserted, because cells contain their genetic material in the form of double-stranded DNA.
The cause of viruses is due to this insertion into the DNA of the cell, which can translocate genes in addition to allow them to take control of the cell for its proliferation, which prevents it from functioning properly.
- Breitbart, M. (2005). Is there a virus here, is there a virus, the same virus everywhere? Trends in microbiology. 13 (6): 278-284.
- Dimmock, N..J .; Easton, AJ; Leppard, K. (2007). Introduction to Modern Virology Sixth Edition. Hoboken: Blackwell Publishing.
- Rei, AM; Lefkowitz, E., Adams, MJ; Carstens, EB, (2011). International Committee on Virus Taxonomy, International Union of Microbiological Societies. Virology Division (ed.). Ninth report of the International Committee on the Taxonomy of Viruses. Oxford: Elsevier.
- Pennisi, E. (2011). Going viral: exploring the role of viruses in our bodies. Science, 331 (6024): 1513.
- Madigan, M .; Martinko, J. (2005). Brock Biology of Microorganisms New York: Prentice Hall.
- Neuman, BW; Kiss, G .; Kunding, AH; Bhella, D .; Baksh, MF; Connelly, S .; et al. (2011). Structural analysis of the M protein as a whole and of the morphology of coronaviruses. Journal of Structural Biology. 174 (1): pages 11 to 22.