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The almost indestructible animal that is helping human beings!

Tardigrade. Heard this name before now?

Tardigrades, also known as “water bears,” are eight-legged microscopic animals capable of withstanding some of the most severe environmental conditions. Tardigrades are notable for being the most resilient animal: they can survive extreme conditions that would be rapidly fatal to nearly all other known life forms. They can withstand temperature ranges from 1 K (−458 °F; −272 °C - close to absolute zero) to about 420 K (300 °F; 150 °C), pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space. They can go without food or water for more than 30 years, drying out to the point where they are 3% or less water, only to rehydrate, forage, and reproduce.

They are not considered extremophilic because they are not adapted to exploit these conditions. This means that their chances of dying increase the longer they are exposed to the extreme environments, whereas true extremophiles thrive in a physically or geochemically extreme environment that would harm most other organisms. They have been found everywhere from mountaintops to the deep sea, from tropical rain forests to the Antarctic.

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Tardigrades are about 0.5 mm (0.02 in) long when they are fully grown. They are short and plump with four pairs of legs, each with four to eight claws.

Tardigrades have truly bizarre genetic constitution (2). Earlier researchers thought that that 17.5 percent of the tardigrade genome comes from other organisms, including plants, fungi, bacteria, and viruses. The water bear was earlier considered to have acquired many of its characteristics not as a result of its own evolution, but through the toil of others in a process called horizontal gene transfer.

Researchers from Japan have now created the most accurate picture of the tardigrade genome, revealing the neat tricks it uses to stay alive. In a new study published in Nature Communications (1), geneticist Takekazu Kunieda and his colleagues from the University of Tokyo present a genetic analysis of Ramazzottius variornatus, arguably the toughest and most resilient species found in the entire tardigrade clan. Their results show that tardigrades have evolved a unique arsenal of strategies to cope with stressful conditions, including a protein that protects its DNA from radiation damage. The new research from the University of Tokyo challenges the earlier assumptions, showing that the vast majority of tardigrade characteristics are truly “proprietary,” and not the result of horizontal gene transfer.

The new study differed from the previous one in some very important ways. The researchers used one of the most resilient tardigrade species on the planet, R. varieornatus, whereas the previous study looked at Hypsibius dujardini, which is among the least tolerant freshwater species of tardigrade.

Also, the researchers successfully eliminated all extraneous bacteria (using commercial chlorine bleach, among other measures), which allowed them to scan the tardigrade genome without any contaminants. This is important because the authors of the original study claimed that an incredible amount of bacterial genes were included in the tardigrade genome.

Lastly, the researchers were able to sequence the tardigrade genome at a much higher level of accuracy, creating a genetic profile that was 100 times less fragmented than the previous one.

Looking at the newly sequenced genome, the researchers observed that the proportion of foreign genes is closer to 1.2 percent, which is much lower than the 17.5 percent claimed last year.

The proportion of 1.2 percent is not so special in the animal kingdom, and thus extensive horizontal gene transfer is not common in tardigrades, if any. “A striking feature of tardigrades is that they have developed—and abundantly express—tardigrade-unique genes, and some of them likely play important roles in tolerance.”

When the researchers transplanted this protein to cultured human cells, the same protections still applied - a finding with potential applications to cellular preservation methods, genomic therapies, and the burgeoning science of transgenics ( mixing the DNA of different animals like injecting the genes of animals into humans. It's the use of any number of recombinant DNA techniques to introduce new characteristics — via genes — into organisms that weren't present before. These changes can either alter the germ cell line, passing new traits down to offspring; or they can affect the somatic cell line, which just changes the individual who receives treatment. Transgenesis can involve the entire organism, or a few individual cells. Transgenic animals are sometimes called chimeras or hybrids. These genetically-mixed animals are often used to model specific human diseases, produce novel materials and tissues, and engineered to withstand diseases, among many other things).

The authors of the new study were able to pinpoint a number of genes and biological processes responsible for the tardigrades’ remarkable survival skills.

For example, its genome contains more copies of an anti-oxidant enzyme and a DNA-repair gene than any other animal. Kunieda says these tools help the tardigrade counteract oxidative stress when it’s dehydrated, and to efficiently repair its damaged DNA.

They also found that the hardy water bear expresses a tardigrade-specific protein that binds itself to DNA. This unique protein, dubbed Dsup, acts like a shield against x-ray radiation, preventing the DNA from snapping apart. This would help to explain why tardigrades are seemingly impervious to radiation, and why they can survive the vacuum of space.

This tolerance to x-rays can be transferred to the cells of other animals. On tests using cultured human cells, the researchers demonstrated that Dsup suppresses x-ray-induced DNA damage by a whopping 40 percent. If this tardigrade-specific protein could be transplanted to live humans, it could improve our own tolerance against X-rays. And perhaps tardigrade biology could be used to make humans more adaptable to space.

Once Dsup can be incorporated into humans, it may improve radio-tolerance. But at the moment, we’d need genetic manipulations to do this. However, Dsup isn’t perfect, as it reduces the damage done by radiation to DNA by approximately half, “which is significant, but still only half.” What’s more, the researchers are confident that tardigrades use other strategies in addition to Dsup to fend off the effects of radiation.

Scientists see big things for Dsup, and other “extremotolerant” characteristics, both those that have already been discovered, and those still waiting to be found. Using these tolerant genes collectively, they could confer enhanced tolerance to other animals. Especially, if dehydration-tolerance can become transferable, it will transform the way we preserve various biological materials, including cells, crops, meats, fish, and the list can become infinite!

Protection and repair of DNA is a fundamental component of all cells and a central aspect in many human diseases, including cancer and ageing. This makes the new paper’s findings highly interesting for medicine. 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.

So if scientists can tap these potentials of tardigrade, we can pack our bags and get ready to travel into space without much fear.

Updates...

A study that has been published in the journal, PLOS Biology says...

Scientists found that the key to their survival is genetic. Dry conditions trigger some of the creature's genes to produce proteins which replace missing water in their cells. Once water is available again it refills the cells dissolving the proteins.

The researchers say understanding this innate survival ability of tardigrades could have benefits for humans, such as allowing live vaccines to be posted around the world and stored without refrigeration.

The scientists also discovered a different set of proteins which can protect tardigrade DNA, perhaps explaining how the creatures can survive radiation.

References:

1. http://www.nature.com/ncomms/2016/160920/ncomms12808/full/ncomms128...

2. http://gizmodo.com/indestructible-water-bears-have-a-genome-that-is...

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