|A tardigrade. / Photo by: Giovanni Cancemi via 123RF|
New experiments and studies involving microscopic animals could change the scientific world, especially in Genetics and Evolution. These microorganisms are the future of discoveries entailing the unknown secrets of space and time including what lies ahead in our world.
Tardigrades, as defined by Nature.com, are small animals mostly in the range of several hundred micrometers in length and comprising approximately one thousand cells, resembling a junction between a naked mole rat and a polar bear.
These animals can survive anything, including the freezing, hostile, radiation-filled vacuum that is outer space. It is possible that there is a link between tardigrades’ indestructibility and their high proportion of foreign DNA.
Indestructible and ‘out of this world’
Research involving this tiny organism often referred to as ‘water bears’ concluded lots of expectations wherein tardigrades are believed to survive extreme environments, including extreme temperature, pressure, radiation, and even exposure to the vacuum of space.
A study published on Nature also reported the sequencing of the tardigrade H. dujardini and demonstrated that as many as 17.5% of the genes of this organism may have been acquired through horizontal gene transfer (HGT) and that these foreign origin genes may be the key to their extreme tolerance with a harsh environment.
“Protection and repair of DNA is a fundamental component of all cells and a central aspect in many human diseases, including cancer and ageing,” says Ingemar Jönsson, an evolutionary ecologist who studies tardigrades at Kristianstad University in Sweden.
This makes the new paper’s findings “highly interesting for medicine”, says Jönsson. It opens up the possibility of improving the stress resistance of human cells, which could one day benefit people undergoing radiation therapies.
Kunieda adds that these findings may one day protect workers from radiation in nuclear facilities or possibly help us to grow crops in extreme environments, such as the ones found on Mars.
Bob Goldstein, a biologist at the University of North Carolina at Chapel Hill who helped to sequence the genome of another tardigrade species, says the research is exciting and clever. He also thinks that the study’s authors are correct in predicting that this is probably just the first of many such discoveries.
“The tardigrade is resistant to a lot of different kinds of extremes,” says Goldstein. And this means that the animals must have many different ways of protecting themselves.
“We are really just at the beginning of exploring the genetic treasure that the tardigrade genome represents,” says Jönsson.
While these animals exhibit mind-boggling abilities, they too are threatened by danger. According to a study published by the Journal of Experimental Biology, Climate change could affect tardigrades’ survival rates.
Researchers studies how Acutuncus antarcticus, a tardigrade species native to the Antarctic, would react to climate change–associated stressors such as dehydration, high temperatures, and increased levels of ultraviolet (UV) radiation. While the organisms were able to cope with individual events, a combination of high temperatures and high radiation lowered their chances of survival. In addition, the researchers report that tardigrades born from UV-irradiated eggs took longer to reach sexual maturity and produced fewer eggs during their lifetime than those hatched from non-irradiated eggs.
The Foreign DNA
|A man has been tested for a DNA sample. / Photo by: Henrik Dolle via 123RF|
After sequencing the genome of the microscopic tardigrade, the only animal known to withstand the extreme rigors of outer space, researchers at the University of North Carolina at Chapel Hill discovered that an unprecedented amount of the organism’s genome – nearly one-sixth – is made up of foreign DNA.
Around 6,000 of tardigrades’ genes come directly from bacteria, plants, fungi and other organisms in a process known as horizontal gene transfer, the transfer of genes between species instead of directly from a parent.
The information changes not only how scientists think about tardigrades, but how they see evolution and the acquisition of genetic material. The scientists’ work was published in the Proceeding of the National Academy of Sciences.
“We had no idea that an animal genome could be composed of so much foreign DNA,” said Bob Goldstein, faculty in the biology department in UNC's College of Arts and Sciences. “We knew many animals acquire foreign genes, but we had no idea that it happens to this degree.”
Another tardigrade superpower discovered: a protective protein that provides resistance to damaging X-rays. And researchers were able to transfer that resistance to human cells. This could further help human DNA to withstand immense levels of radiation.
“Tolerance against X-ray is thought to be a side-product of [the] animal's adaptation to severe dehydration,” says lead study author Takekazu Kunieda, a molecular biologist at the University of Tokyo. According to Kunieda, severe dehydration wreaks havoc on the molecules in living things. It can even tear apart DNA, much like X-rays can.
The researchers wanted to know how tardigrades protect themselves against such harsh conditions. So Kunieda and his colleagues began by sequencing the genome of Ramazzottius varieornatus, a species that is particularly stress tolerant. It's easier to study processes within the tardigrade cells when the animal's genome is inserted into mammalian cells, says Kunieda. So researchers manipulated cultures of human cells to produce pieces of the water bear's inner machinery to determine which parts were actually giving the animals their resistance.
Eventually, Kunieda and his colleagues discovered that a protein known as Dsup prevented the animal's DNA from breaking under the stress of radiation and desiccation. And they also found that the tardigrade-tinged human cells were able to suppress X-ray induced damage by about 40%.
Much more unknown secrets are yet to be revealed with tardigrades especially with other microscopic animals that lie in our world. Further, the researches that scientists continue to conduct would ultimately end up being useful as these information integrate advances in medicine and other related fields.