To prove this, most animals have less than one percent of foreign DNA and the rotifer which is a freshwater zooplankton, and previously held the record of the most foreign DNA in any animal, had only half of the tardigrade’s foreign DNA.
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Amazingly, research shows that a large portion of its genome comes from “foreign” DNA. It can also withstand temperatures from just above absolute zero to well above the boiling point of water, can cope with ridiculous amounts of pressure and radiation, and can live for more than 10 years without food or water. According to co-author of the study, Bob Goldstein from the University of North Carolina, the team had no clue that this animal’s genome will be composed of so much foreign DNA.
By grabbing DNA from other organisms, the creatures, also known as tardigrades, have adapted to extreme environments, scientists find.
The eight-legged water bear – a hardy, nearly microscopic animal resembling its mammal namesake – gets a huge chunk of its DNA from foreign organisms such as bacteria and plants, scientists have revealed.
The researchers say they’ve detected nearly 6,000 genes in the water bear genome that are foreign, mostly originating in bacteria but also coming from plants, types of fungi and a number of single-celled microorganisms. And it’s this incredible variety of genes that researchers suggest has allowed the water bear to survive in such extreme conditions.
Since we see that many [horizontal gene transfer] genes in tardigrades have known or suspected roles in stress tolerance, it sets up an interesting “chicken and the egg” scenario. Under intense stress, such as punishing dryness, the water bear’s genome breaks up into tiny pieces, the research team explained. Moreover, tardigrades can fix their damaged DNA as the cell rehydrates and stitch in the foreign DNA in the process, creating a mosaic of genes that come from different species. I mean, when is the last time you met an animal that could survive being dehydrated for years at a time?
Lately, researchers were able to discover an organism on the face of the Earth that has the ability to steal DNA from other organisms. As they re-hydrate, their cell walls become porous and leaky, and fragments of DNA from the desiccated organisms around them can flow inside and merge with the animal’s rejuvenating DNA. But what’s really exciting is that it provides new insight into exactly how life evolves.
“We think of the tree of life, with genetic material passing vertically from mom and dad”, Boothby said.
We normally think of genetic material being passed down from one generation to the next, but as horizontal gene transfer becomes better understood, it offers a chance to better understand the process of evolution and how genetic material is inherited, Boothby says.
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Water bears may be the ultimate borrowers. So instead of thinking of the tree of life, we can think about the web of life and genetic material crossing from branch to branch. “We are beginning to adjust our understanding of how evolution works”.
