Viruses are behind the origin of the placenta that has favored human evolution
In the oceans alone there are 10 billion more viruses than stars in the known universe
The microbiologist Martínez García has discovered one of the most abundant viruses in the sea
If you are reading this it is thanks to viruses: the placenta that enveloped you before birth has a viral origin. Forget that phrase that defines them as “bad news wrapped in a protein.” Viruses are fascinating, terrible and “beneficial to life in the long term,” he tells us. microbiologist Manuel Martínez García (Alicante, 1979). It all depends on the scale with which they are measured, whether we look at them as individuals or as a species. As individuals they can kill us, as a species they contribute to our evolution.
They are tiny and abundant. Only in the oceans, the amount of virus is 10 billion times the number of stars known in the universe. A professor of mathematical biology estimates that if we put together all the SARS-CoV-2 coronaviruses active at any given time around the world, they would take up half a can of soda. And just with that, the latest coronavirus has paralyzed the world and killed four million people. The black plague decimated the European population, the 1818 flu killed 50 million people, HIV has already caused more than 35 million deaths from AIDS … What good can viruses have?
We have asked the researcher at the University of Alicante Manuel Martínez García. Its trajectory is not frequent. After a research tour abroad, Professor Martínez García left the possibility of directing a laboratory in the Columbia university to return to Spain. Here he has developed a technique to identify viruses that the scientific journal Nature quoted in a recent article. With her they have discovered one of the most abundant viruses in the world, so elusive until now that they would have liked to baptize him with the name of the elusive spy 007.
Question: there are many contradictory hypotheses about everything that surrounds viruses, but not about an elementary question: what is a virus?
Answer: not much discussion. A virus looks a lot like a walnut. The nut carries a seed inside, which contains the genetic information: a ‘book’ in which what it is going to do is written. And then it has a capsule that surrounds it. A virus is similar because it has a capsule, made of proteins, to protect the most valuable thing it has, the information that keeps what that virus has to do, but there is a big difference. The information that this virus stores is very brief, it is a very short ‘book’. What it has done is to save information and in this saving process, the virus has lost its ability to replicate itself and needs information and the machinery of cells.
Unlike cells o bacteria, viruses cannot replicate on their own. Is that why it is still debated whether they are really life?
It seems to me that it is a very philosophical question and I honestly think that it is a diversion. We will find reasons against and for. I sometimes doubt if it is life or not. Sometimes I think that they are a reduction of life, if we understand by life the capacity in which we keep the machinery to replicate ourselves. If we reduce that and we manage to remove almost everything except the essentials, it would be a very reductionist way of life, in which we depend on another cell to replicate ourselves. But other times I think that they are not life, that they are inert elements with the capacity to harm or bring benefits.
It is not only debated whether they are life or not. Another mystery is knowing what its origin was. Did viruses precede cells or did they come after?
It is a subject that provokes a lot of debate. There is no consensus. Everything we say is still very difficult to verify hypotheses. Why? Because there are no fossil records as occurs, for example, with vertebrates.
Earlier you mentioned reductionist hypotheses. What do they hold?
That viruses appeared after cells, they come from cells that were losing genes until they stayed in a very reductionist and parasitic lifestyle that depends on others because it has lost genes throughout its evolutionary history.
What other hypotheses are handled?
Other hypotheses say that they could be the origin of that protolife. We would have a replicating molecule, which is RNA. RNA has a special capacity that we call catalytic, it can make reactions. This hypothesis says that viruses originated in that proto-life, with genetic material that was RNA, which had that self-replicating capacity. That capsule grew, incorporating genes and metabolic activities, ceased to be parasitic proto-life and evolved into cells. But the original lineage did not disappear and viruses with that minimal capacity continued to exist. In all of this we eventually hit a dead road. We have nothing left of what existed 4 billion years ago.
Can new viruses be emerging right now?
Without a doubt. While you and I talk, new species appear, new variants. But that is the grace of life, that it is not static because, then, we would not be what we are now. We could not have perpetuated life. The possibility of changing the ‘book’ of genetic information is what allows us to perpetuate ourselves, let’s talk about viruses or a rhinoceros or a human being. Let’s imagine a computer that has a static code that cannot be changed. How are we going to have a better computer, how is it going to evolve, if we are not able to change the source code, the important things that give instructions to the computer. There is no way we can improve. Years would pass and that computer would become extinct. Using this metaphor, viruses have the ability to change a lot and mutate a lot in order to adapt to changes in cells.
So are viruses a good thing?
It is absolutely logical to associate viruses with the negative and more with what is happening. It was like this before the pandemic. It is obvious that if a virus infects you it is bad. As people we think like this, but if we think in the long term, which is how life thinks, in millions of years, viruses are essential in many processes.
A recently discovered example related to the human body. From the mouth to the end of the digestive tract, we have an epithelium that is in contact with many external agents, with bacteria that can be pathogenic. Now we know that this epithelium is covered by a lot of viruses that adhere to our mucosa. They are not viruses that infect us, but rather act as a containment barrier. There are other examples, that of the placenta is not even necessary to mention it, it is well known …
Do not believe, it may not be so well known outside of the scientific field.
The placenta that nourishes and protects the fetus has evolved thanks to the fact that a virus infected and provided a series of genes that gave specific information for the placenta to end up originating as we now understand it. If we looked back and could talk to the virus, we would have to thank him. We live because that happened. Our evolution has probably been successful thanks to the fact that these viruses infected us in the past. And now it keeps happening. Viruses are giving genes to the human genome.
What percentage of our genome is of viral origin?
Around 9% or 10%. It is a lot. Our genetic ‘book’ is largely written by writers who are viruses. If that information is kept in our ‘book’ it is because it has a role. That is one of the great challenges that science is trying to decipher: why do we preserve that information and what function does it serve?
The microbiologist Manuel Martínez García (first from the right) with his research team
In the Nature article that mentions you, they remember that in the oceans alone there are 10 billion times more viruses than stars in the known universe. Thus, from the outset, the figure is intimidating when we see what a single virus has done to the world …
It can be calculated because we have tools to count how many viruses are in a drop of water. Now that summer is coming, when a wave hits you and you swallow some water, you are swallowing hundreds of millions of bacteria and that number multiplied by ten will be viruses.
However, only a few are capable of infecting us, right?
99.9% of the viruses that we have on Earth are absolutely harmless for humans. Not only innocuous, we need them. And the cells and bacteria they infect often need them to survive. Someone once said that viruses are like the oil that we add to the engine, to the gears so that they do not make noise. They lubricate that ecosystem.
There are billions of viruses, but only 9,000 species have been identified, most in recent years.
Yes, a tiny part of what exists. It is because it is very complex. We need sophisticated gadgets. It costs money. Viruses are very diverse. Also, it is not easy for a virus to grow in a laboratory because it needs its cell to grow. The first thing you need to do is grow that cell and that is not easy because we do not know the nutritional and physiological requirements of many of the cells that viruses infect. That is why we need to use strategies that overcome these difficulties and that is where the technique that we have developed comes in and it is one of the reasons why we are cited in Nature.
Our technology allows us to overcome that problem. Without having to have the host cell isolated in the laboratory, we can identify this virus, know its genome, know its ‘book’. It’s called Single Virus Genomics and it has been recognized as interesting from a scientific point of view. We take any sample, be it seawater or saliva, we separate each virus particle with a machine and isolate it from the others. Then we break the capsule and take the genetic information to read it. But since we don’t have the technology to read something so tiny, we need to make copies and copies and copies … And when I have millions of copies I am already able to read the book. So we can read the genetic information of the virus without having to know which cell it infects.
Nature says that you have identified one of the most abundant viruses in the sea. You have christened it 37-F6, but you wanted to call it 007 because of its ability to not be detected.
Yes, I will always regret it, because 007 is always working hidden there and is everywhere… It is one of the most abundant viruses on the planet, perhaps the most abundant, and we did not know it was there. With the tools we had we were so myopic that we were not seeing it, but with our technique we were able to discover it.
As a species, you say, we must see viruses as agents that help modify our genetic ‘book’ of instructions and, therefore, favor our evolution. However, when a new virus jumps from its reservoir to the human species, the price is usually devastating in the short term in individuals, it is not much consolation to be simple links in that long evolutionary chain.
Viruses are not ‘interested’ in their host dying. If the host dies, they die with the host. You have to think long-term in biology. Life does not think of the years that a person lives, life thinks of millions of years. In the long term, the relationship between a virus and its host is mutualistic. That is, there is a certain benefit. We know that viruses are capable of providing genes, new metabolic capacities, to cells. In that long-term process, viruses constantly bring us beneficial things, but we pay a price. In the short term, cells die, but in the long term, no: the species survives. It is a contradiction. In the short term, if a coronavirus infects me and I have the misfortune that something happens to me, I will experience it negatively. But, probably, as we have seen in evolution, as we saw with the placenta, they continually give beneficial things not only to us, but to any organism. Ability to grow better, exploit new resources … And that evolutionarily must be seen as something positive.