When the first pandoravirus was described a few years ago, scientists were clear that they were dealing with something unprecedented.
Pandoraviruses are part of the family of giant viruses and can be up to 10 times larger than a common virus, even measuring as much or more than other small bacteria.
In addition, they have many more genes. The influenza A virus, for example, has a genome of about eight genes. A pandoravirus, like salinus, can have about 2,500 genes.
Research on the giant viruses has discovered things as surprising as the fact that they are often targeted by cannibalistic viruses, i.e. viruses that parasitize other viruses.
And recently, a study found indications that some pandoraviruses generate a membrane potential only possible through energy production.
This study led by the Mediterranean University Hospital Institute of Infections in France reconsiders the scientific dispute about whether pandoraviruses are a type of virus or whether we are facing a biological group that has yet to be categorized.
However, other experts remain skeptical of this possibility, reasoning that there is still much research to be done in order to consider another biological classification.
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The first giant viruses were described in 2003 and the first one was called mimivirus. Since then the so-called pandoraviruses have been discovered and their genomes studied.
They are characterized by their size, greater than 200 nanometers, when common viruses are defined as being less than 200.
The giant viruses are observable under the light of an optical microscope, while the other viruses can only be seen with an electronic microscope.
But it was not until 2013 when the term pandoravirus was coined, when one of the largest, salinus , was discovered in the Tunquén wetland in Chile.
It is called a pandoravirus in reference to the ‘pandora’s box‘, a mysterious box mentioned in Greek mythology. It was named this way because its genome encodes 80% of completely unknown proteins that make this type of virus like a box full of surprises. One of them is the recent discovery of the energy metabolism.
Are they really viruses?
Pandoraviruses and giant viruses, according to researchers in the recent study, have changed the definition of viruses in several ways.
For example, the first time it was described that viruses could also be infected by other viruses was through analysis of these giant entities.
Now, with the discovery of an electrical gradient, this group of scientists suspects that pandoraviruses may also be capable of producing their own power.
Energy production is associated with the vivocellular world, but certainly not with viruses which, by definition, are not considered living beings, since they parasitize an organism and exploit its energy metabolism in order to replicate.
The findings question the definition of viruses and could suggest that pandoraviruses are simply not viruses.
Structurally, pandoraviruses remain viruses because of the way they replicate. There is still a lot of research to be done to see if they could be something else, but what is certain is that they are shedding more light on biology.
The study on the energy production of pandoraviruses is preliminary and has not yet been peer-reviewed.
In light of the recent coronavirus pandemic, there is a growing trend to classify viruses based on whether or not they can infect humans.
But the world of viruses is very big. pathogens are only a slightly more studied aspect. Right now there is no data that suggests that they can be dangerous, the expert concludes.