Water bears or tardigrades are microscopic critters with impressive survival skills that reportedly can withstand freezing, radiation, desiccation, the emptiness of deep space, and they even reportedly survived five mass extinctions. But a group of scientists found that water bears can survive extremes through foreign DNA acuisition.
Researchers at University of North Carolina at Chapel Hill were able to sequence the tiny animal’s genome and the findings were stunning. Analysis showed that up to 17.5 percent of their genomes is made up of DNA coming from non-animals such as fungi and bacteria.
Scientists explained that tardigrades acquired the foreign DNA through a mechanism called horizontal gene transfer, which is widely spread among single-cell organism but nearly nonexistent in the animal kingdom.
However, researchers said it was the first time they found a creature with 1/6 of its DNA made up of other organisms’ genetic material. The previous record holder is a microscopic plankton which has 9 percent of its DNA of foreign origin.
Bob Goldsteain, co-author of the water bear study, recently said that his team was not able to decipher yet what creatures donated genetic bits to the tardigrade, but they have a theory on how that happened.
The team estimates that the microscopic animal may resort to horizontal genetic transfer when it is under a lot of environmental stress. Water bears love wet environments, but when they are deprived of water and become desiccated, their DNA breaks apart.
Yet, biologists long knew that when moisture returns, they will re-hydrate and go on with their lives as nothing happened. Scientists believe that during the re-hydration process, they absorb nearby DNA of other desiccated creatures through their cell walls. Foreign DNA is next incorporated in the animal’s genome, helping it to rebuild DNA from pieces.
If the genes are absorbed by a germcell, foreign DNA fragments can be passed on to offspring for generations to come. The team also learned that foreign DNA acquisition may be linked to stress tolerance.
Goldstein, however, admitted that his team were still struggling with a ‘chicken and egg scenario.’ The scientist’s personal opinion is that the animals have beefed up their survival skills over time through gene acquisition because they were under a lot of environmental stress. As a result, the amount of foreign genes that entered their system mounted over time so that today the better at survival the creature is the more foreign DNA it can ingurgitate.
Image Source: Wikipedia