Are Pandora viruses a fourth domain of life?

Chris - It's amazing. What do you know about it Damon? Tell us what you know about it.

Damon - I don't know much. I think they said you could even see it with a standard microscope. It was that large.

Chris - Yeah. It's published in Science this week. It's by a group in France who discovered this. Actually, they discovered this massive virus in a pool of freshwater, a pond basically, near Melbourne in Australia. They also found a very similar virus off the coast of Chile and these viruses, they've dubbed the Pandora viruses because when they had a look at them genetically, then it was anyone's guess what was in there because they did not bear any resemblance to any kind of life than we'd ever found before. So, we talk about life having 3 established domains. There's the eukaryotes - cells like ours. There's prokaryotes - they're bacteria, we know about those and then there's another sort of ancient evolutionary spinoff called the archaea. And we were very happy that all life on earth fitted into those 3. Now, we've got these viruses that have come along. That a) are huge, they're more than a thousandth of a millimetre across which is in virus terms, that's like you walking down the street and bump into someone 60 feet tall. They are enormous, these viruses and they bear no genetic resemblance to anything else that exists on the earth. So, the big questions are, why do they exist? Why are they so huge? I mean, what they do is they live on amoebae, these little single-celled organisms, they prey on them. As I said, absolutely enormous with a huge genome. They've got 2.5 million genetic letters in their genome, which is massive. I mean, it's 10 times bigger than your average virus does. So, scientists are saying, 'well, when we look in the sea and we find all these bacteria that we can't grow in culture.' Actually, they might not be bacteria that we can't grow at all. They might be viruses. These massive viruses that we previously hadn't realised because the people who write the paper have said - well actually, 13 years ago looking in the literature, people described these funny particles and they didn't know what they were. They thought they were some funny hard to grow bacterium because they were so big, because they're literally 10 times bigger than a normal virus. And now, they realise they are a virus, but we don't know what the hell they are.

Dave - So, when you say then nothing like anything else say in life basically, so if they're a virus, surely, they must be hijacking another animals sort of replication machinery. So surely, it can't be that different otherwise it wouldn't work.

Chris - Sure, the genetic code is exactly the same, so a gene in them will the same sort of gene, it would work the same way in one of our cells and vice versa. They haven't rewritten the genetic code, but they prey on amoebae and they just make more new viruses and it's interesting because what most viruses do when they make a virus particle is that they make the coat of the virus and then they stuff the genetic material inside. These things start basically almost like they're knitting a jumper. They knit, the coat as well as the genetic material into it all at once. So, they have this really weird way of growing and they have genetic material, they don't use genes which are used by any other organisms that we know of apart from them. So, exactly why they exist and where they've come from, we don't know. They are completely alien species. Are you spooked, Damon?

Damon - Not so much spooked as just confused.

Ian - I'm just wondering if these are one of the hangovers from the Precambrian when you had a huge diversity of different life forms and some of those went on into the Cambrian and produced really exotic things that then suddenly vanished. Maybe these were something really exotic, but they just happen to have been saved in the deep oceans and places like that of obscure places, and they're part of what went on to be the Burgess Shale type things.

Chris - Now, they've been discovered, I guess we'll look in and we'll find out, but it's very interesting, isn't it?