This is the first in an EICES series entitled, “Notes from an increasingly lonely planet” which considers the latest developments in biodiversity science and what they tell us about life in an age of mass extinction.
In Nature|News (18 July 2013), where one can check out the latest happenings in science, we learned that when Jean-Michel Claverie and Chantal Aberget from Aix-Marseille University in France discovered their new species of humongous killer virus, they experienced one of the most exciting things that could ever happen to any of us – they discovered a new form of life! They didn’t just discover a new species, like the new species of tailor bird, chalice coral, noctuid moth, thread worm, catfish, gesneriad flower, or other new species discovered this year. What they discovered was not a bacteria, plant, or animal and though it behaved like a virus – it seems to be something entirely different, something completely alien.
And what’s even more amazing is that this new life form, or NLF, was found right here on Earth.
Most of us imagine that if we were to encounter an NLF it would be from outer space, and given the way NLFs are usually portrayed in the media, it would not be a very positive experience. If we weren’t abducted and probed by aliens, more than likely we would be eaten, possessed, or torn to shreds for no apparent reason. Failing that, the alien might simply vaporize us, also for no apparent reason. There have been TV shows in which alien NLFs disguise themselves as humans, befriend us, and then eat us. In the movie, The Arrival, aliens settle beneath the earth where they set about terraforming our planet by releasing greenhouse gasses into our atmosphere that eventually kill our species. (Climate change deniers must love this movie!) In Skyline, aliens came to harvest our brains to implant in their own life forms. This summer, in the movie Pacific Rim, aliens send giant Godzilla-like creatures through an underwater portal to rise up out of the sea and stomp us to death. Many aliens avoid direct confrontation and just come at us in giant space ships and blast the bejeezus out of us with death rays.
I love this stuff – and if it is in IMAX 3D, all the better! Aside from the entertainment of seeing how people imagine NLFs, these movies almost always end on a positive note. No matter how certain Earth’s annihilation seems, humans figure out how to cancel the apocalypse, to paraphrase Stacker Pentecost, played by Idris Elba in Pacific Rim. When you work on global environmental issues, it’s kind of uplifting to see us rally together to save the planet.
Perhaps the most interesting alien NLF movie so far is Species. In this movie, the aliens dispense with building space ships to invade Earth. Instead, they send us the code for their DNA and instructions on how to insert it into our own to make an alien-human hybrid right here on Earth. We would start with an ovum, but once the hybrid grew up we could interact with it and learn more about alien life. The scientists decide this is a terrific idea–big mistake! The creature who emerges, though it grows very rapidly to be a very handsome woman (played by Natasha Henstridge), has an insatiable appetite for sex with healthy men and a desire to make lots and lots of alien babies that grow up to be gruesome killers. Turns out the whole thing was just another alien plot to wipe us out.
Though ultimately Species does not stray too far from the tried and true formula of aliens-from-outer-space movies, what’s fascinating about the movie is that the alien was essentially human, but with a lot of non-human sequences in her DNA. Did that make her a NLF? While definitely monstrous in appearance, she looked like a woman just with scales, spines, tentacles, armored plates like insects or chitons, and other familiar biological structures. She didn’t have anything particularly novel. In fact, creatures in most alien-invasion movies are actually quite familiar – they have limbs, teeth, eyes, claws, wings, they drool, spit, and even fart explosive gasses. Oh yes, and they love to eat. No matter how big or fierce or nasty in disposition, they still look like insects, lizards, or mutant humans. I would argue that most movie aliens from outer space probably don’t qualify as NLFs – they are just another form of animal or, though more rarely, another form of plant or fungus as in The Thing, The Body Snatchers, or The Day of the Triffids.
So to be a new life form isn’t about being a new species. It’s about having a lot of unique DNA that encodes genes for traits most other species don’t have.
So how many life forms are there? Thousands? Millions? This is one of those mind-boggling facts about life – there are only three. In spite of there being ten million species on Earth, they all fall into just three forms or domains, as they are called in biology: the Eukaryotes, the Bacteria, and the Archaea. That’s beyond strange. I would have thought there would have been hundreds or maybe even thousands after 3.5 billion years of evolution. But there are just three domains.
The big news is that we may be on the verge of adding a fourth new life form. The creature Claverie and Aberget discovered was a humongous killer virus unlike any known in the biosphere at the time. Fortunately, this virus doesn’t attack us. It attacks and kills amoebae, those amorphous single-celled microorganisms common in soil and freshwater ecosystems.
Of course “humongous” is a relative term. Life doesn’t come any smaller than viruses, if one is even willing to consider them living things. Most viruses are between 5 to 300 nanometers long, or less than a hundred-thousandth of an inch. They are so small you can’t see them, at least not in any detail, even with the best of light microscopes. You can “see” them, however, with electron microscopes. There are bigger viruses, but the virus Claverie and Aberget found, officially named Megavirus chilensis (they discovered it in Chile), was about the biggest anyone had ever seen. Amazingly, you can readily see these with a good microscope.
What Claverie and Aberget found may be amazing as a humongous killer virus unlike any known before, but if it’s just a virus, why would it be considered an NLF? After all, if we are going to dismiss alien NLFs from outerspace as just a bunch of Eukaryotes, even though many of them are humongous killers, what makes M. chilensis so special?
In the journal Science (19 July 2013, Vo. 341, pp. 281-286), Nadège Philippe and colleagues, including Claverie and Aberget, report on their discovery of possibly two new species of humongous killer viruses which they called Pandoraviruses. They collected the Pandoraviruses’ DNA and analyzed it and they discovered DNA unlike any we’ve ever seen before – some of the genes looked like eukaryotic genes, some like bacteria, and some like virus genes. But they could find nothing that looked like the key genes a eukaryote would have and while they did have some genes that looked like megavirus genes, they did not have some key genes one would expect for viruses? So they may only look like viruses and behave like viruses and have some viral genes, but for all intents and purposes, they may not be viruses. And here’s the kicker – most of the genes they have don’t occur in any other species for which we have gene data.
So Pandoraviruses may not, in fact, be viruses, and may not belong to the other three domains of life. They have some things that look familiar, but their DNA is so unique, they could be the real deal – genuine NLF!
At a time when the diversity of life on Earth is vanishing incredibly fast, the discovery of Pandoraviruses couldn’t have come at a more important time. It has a lot to tell us about the living world, especially when considering the bizarre world of microorganisms as we’ll do when next we take notes on the extraordinary diversity of our increasingly lonely planet.
Shahid Naeem is professor of ecology, Department of Ecology, Evolution and Environmental Biology, and director, Earth Institute Center for Environmental Sustainability.