This Virus Shouldn't Exist (But it Does)

Hidden in the microverse all around you, there's a merciless war being fought by the true rulers of this planet: microorganisms. Amoeba, protists, bacteria, archaea, and fungi compete for resources and space. And then there are the strange horrors that are viruses, hunting everyone else. Not even alive, they are the tiniest, most abundant, and deadliest beings on earth, killing trillions every day. Not interested in resources, only in living things to take over.

Also, we thought, turns out there are giant viruses that blur the line between life and death. Considerably smaller than your cells or even bacteria, viruses are nothing but a hull, a tiny bit of genetic material and a few proteins. No metabolism, no way to propel themselves, no will or ambition. They float around aimlessly and hope to stumble upon a victim to infect and take over. Viruses are so simple that we're not sure if they should count as living things or not. Some scientists argue viruses are alive; others think that the cells they infect are the actual living viruses—hybrid organisms called viral cells—and the viral particles are more like seeds or spores. Many others think viruses are just dead material.

The origin of viruses is a mystery because how can something that needs victims to make more of itself emerge in the first place? There are many ideas. Viruses may have been essential steps in the emergence of life, or maybe they started out as escaped DNA from cells that became really good at making copies of themselves. Maybe they are the descendants of truly lazy parasites that let others do all the work for them. The current thinking is that viruses probably emerged multiple times from different origins, but we simply don't know for sure yet.

Whatever the truth is, viruses are the most successful beings on this planet. There's an estimated 10,000 billion billion billion viruses on earth. If we put them all next to each other, they would stretch for 100 million light-years, 500 Milky Way galaxies wide. Very recently, viruses became even weirder when scientists found a completely new type: giant viruses nicknamed gyruses. Not only did it break all sorts of records, but it also questioned many assumptions we had about their nature. Gyruses even come with their own parasites: virophages—viruses that hunt other viruses—which seemingly makes no sense at all.

Since we identified the first one in 2003, it seems like these giants are everywhere we look: in the oceans, in water towers, in the guts of pigs, and the mouths of humans. They are even weirder than we thought. Gyruses look funny, like hairy geometric forms or mini pickles—not much larger than all viruses we knew before, which explains how they could hide in plain sight for centuries. Scientists saw them under their microscopes and just thought they had to be bacteria. It's like suddenly discovering there are elephant-sized ducks everywhere.

Most gyruses we've found so far hunt amoebi and other single-celled beings. When they find a victim, they connect with it and use its natural processes to enter the cell. Like all viruses, their goal is to misappropriate the victim's infrastructure and procreate. Imagine a mouse crawling into your mouth and using your guts, bones, and fat tissue to build a mouse factory. The gyrus unloads its attack proteins and genetic material, rearranging the cell from the inside. Its structural elements, protein production machinery, and large amounts of mitochondria for energy are changed to become an actual factory called viroplasm. Some gyruses even construct a membrane to shield them from the cell's antiviral defenses.

Once finished, the viroplasm begins to assemble new gyruses, using the victim up from the inside until it's filled up. Finally, the invader usually orders the cell to self-destruct and releases new gyruses to look for new prey. But what makes gyruses special is not their modus operandi or their size, even—it's that they are much more complex than thought possible for a virus. Your cells have around 20,000 genes; a typical bacterium has a few thousand genes. The coronavirus has around 15; HIV or the flu, around 10. The number of genes alone is certainly not everything.

The tomato, for example, has 35,000 genes, but generally, we think of life as a complex system. So, below a certain complexity level, something may be closer to dead material rather than a living organism. But gyruses can have hundreds or even thousands of genes, blurring the line between living and dead things. And it's not just the numbers that are special, but also what these genes do. We used to think of viral genes as the simplest of instructions—just enough to overcome the defenses of their victims and make new viruses. But many gyrus genes are completely unique—basically, mystery genes.

Even more confusing, a huge selection of their genes that are actually hallmarks of living things—genes that regulate nutrient intake, energy production, light harvesting, replication, or are just necessary to keep cells alive. Some recent studies have even suggested that some gyruses with very complex genomes may be able to maintain a basic level of metabolism on their own, which, if true, will shake up what we thought of viruses even more. We still don't know anything for sure, but one idea about gyrus genes is that they might fundamentally alter the physiology and evolution of their victims by integrating their own genomes and merging with them into chimeric organisms. Or, the other way around, take some host genes with them and be changed themselves.

For billions of years, gyruses may have been existing alongside and infecting cells, exerting an unseen influence on the development of life—not just as a parasite but jerking evolution in different directions by mixing genes around in all directions. This brings us to another unique thing about them: virophages— the viruses hunting gyruses. The concept itself is a bit mind-boggling. How can a thing that might be dead hunt another thing that might be dead too?

Let's look at one of them: the viruphage sputnik is hunting a gyrus called mama virus that itself is hunting amoebi. Sputnik is a tiny, minimalistic virus that doesn't even have the genes and tools to replicate itself. What it does have is the ability to hijack the viroplasm factories of mama viruses. So, virophages need their victim, the gyrus, to infect their victim, an amoeba. First, and then they can parasitize it. A memovirus viroplasm infected by sputnik can only produce very few new gyruses, and among these, many are deformed and broken—unable to infect further cells.

Instead, it makes loads of new sputnik viruphages. Other virophages are even more subtle: when they infect a viroplasm, they just integrate their genetic code into the newly produced gyruses like sleeper agents. The next time one of these infiltrated gyruses successfully infects a cell, it produces mostly viruphages instead of gyruses. Gyruses are not completely defenseless, though. A few years ago, the world was in awe when scientists discovered CRISPR, a bacterial defense system against viruses.

It turns out some gyruses have a system that might be similar—a sort of gyrus immune system against virophages. In turn, virophages can also be used as an anti-gyrus defense mechanism by living cells. Some protists have been found that integrated the genetic code of virophages into their genome and kept it. When the protists were infected by gyruses, they used the code to create virophages themselves to take over the gyrus factories. In the end, the protists would still be killed by the gyrus infection, but instead of releasing gyruses to kill its buddies, it released virophages to hunt them.

The amazing thing about everything we've told you in this video is that we're still very much at the beginning. It's not even been 20 years since the discovery of gyruses and virophages. There is so much going on in the microverse. Life is not an isolated event but a ping pong game of trillions of organisms and viruses. So when you feel down and like there's not that much new to discover, think of gyruses and all the other elephant-sized ducks all around us— invisible until we look more closely.