A recent study published in the Proceedings of the National Academy of Sciences has revealed that water bears have super resistant DNA. As if these water species hadn’t been sufficiently strong, the fact that they have 17.5% foreign DNA also contributes to reinforce their durability.
Tardigrades, as researchers have scientifically named them, are highly resistant water micro-organisms that can resist even in the most difficult conditions. At the first look, these species don’t seem to have anything special that allows them to resist. They have eight legs and they live in places populated with water, be they in Antarctica or near the sea.
Nevertheless, a more recent study has revealed to us that tardigrades have a special form of DNA, which makes them even more resistant. Unlike rotifers, whose DNA is 9% foreign, water bears have a 17.5% foreign DNA. Tests have revealed that these genomes have been acquired through horizontal transfer from bacteria, fungi and other virus-like organisms.
Researchers managed to identify the non-animal DNA sequences by isolating them from the rest of the genes. They have been impressed by the large percentage of foreign genes that this water species contains. This is the first micro-organism with one sixth of its DNA coming from non-animal beings, but rather from plants and bacteria.
Even though they have deciphered the mystery of water bears’ resistance, there are still many aspects that remain to be solved. According to biologist Bob Goldstein, future studies have to focus on the identification of the species where these genomes come from. Furthermore, scientists want to understand how tardigrades have acquired this special DNA.
Investigators have come up with many possible explanations, but they haven’t opted for a particular hypothesis. They believe animal and non-animal DNA sequences have been mixed due to tardigrades’ desiccation and re-hydration.
More specifically, tardigrades, which live in extremely moist environments die because they simply dry out in the absence of water. Their body cells disintegrate, but some may be revived when water returns. The same process could be possible for other micro-organisms, as well and their desiccated cells could get incorporated by the extremely porous walls of the water bears.
Scientists think this process might also be the key to tardigrades’ eternal survival. The more stress factors they face during desiccation and de-hydration, the more powerful they become because their DNA acquires new genes that are resistant to the new stress factors. Yet, additional researchers have to be conducted to be truly convinced of tardigrades’ survival skills.
Image source: www.nasa.gov