No animal on Earth is stronger than tiny tardigrades, as they can survive freezing at -272 degrees Celsius, exposed to the emptiness of outer space, and even exposed to an amount 500 times greater than the amount of X-rays that kills humans.
The harsh conditions that tardigrades endure
In other words, this organism can withstand conditions that do not exist on Earth. This amazing flexibility, along with their endearing appearance, has made tardigrades a favorite among animal lovers. But apart from that, researchers are looking to these microscopic animals, roughly the size of a dust moth, to learn how to prepare humans and crops to withstand the rigors of space travel.
The slow-paced’s toughness stems from its adaptation to its environment, which may seem surprising, because it lives in seemingly comfortable places, like the cool, damp clumps of moss that dot garden walls. Because they live in such habitats, as well as their short and stout appearance, some people call tardigrades water bears or mossy piglets.
Drought resistance of slow paced
But it turns out that the wet habitat of tardigrades can dry out several times a year. This drought is a major disaster for most living things, as it destroys cells in the same ways that freezing, vacuum and radiation do.
On the one hand, dehydration leads to high levels of peroxides and other reactive oxygen species. These toxic molecules cut the cell’s DNA into short pieces – just as radiation does. Dehydration also causes cell membranes to wrinkle and crack. It may break down the tiny proteins, rendering them useless. But tardigrades have devised special strategies to deal with these types of damage.
Above: When the slow-paced dries out, its cells make long, cross-linked proteins (shown) that coat and protect cell membranes.
When tardigrades dry out, their cells emit many strange proteins that are unlike anything found in other animals. These proteins in water are soft and shapeless. But as the water disappears, these proteins self-assemble into long, criss-cross fibers that fill the inside of the cell. Like styrofoam granules (pellets made of polystyrene foam), these fibers support cell membranes and proteins, preventing them from cracking or sloughing off.
And there are at least two species of tardigrades that also produce another protein that no other animal on Earth has. This protein, called a “damage blocker”, binds to DNA and protects it from reactive forms of oxygen.
How slow pacers get us to the stars
And mimics of tardigrades could one day help humans colonize outer space. Food crops, yeast and insects could also be engineered to produce slow-paced proteins, allowing these organisms to thrive more efficiently on spacecraft where radiation levels are higher than on Earth.
It is reported that scientists earlier inserted a gene for a “damage inhibitor” protein into human cells in the lab, and many of these modified cells escaped levels of X-rays or peroxide chemicals that kill normal cells. When introduced into tobacco plants – an experimental food crop model – the gene appeared to protect the plants from exposure to a DNA-damaging chemical called ethyl methanesulfonate. Plants with the added gene grew more quickly than plants without it. Also, plants containing this protein showed less DNA damage when exposed to ultraviolet light.
Above: Microscopic tardigrades can withstand extreme cold, drought and extreme levels of radiation thanks to unique molecular adaptations.
The slow-paced proteins are showing early signs that they may be protective in humans. And when human cells were modified to produce these proteins, they became resistant to camptothene, a cell-killing chemical agent, researchers report. The slow-paced proteins do this by inhibiting apoptosis, a cellular approach to self-destruction that often kicks in when exposed to harmful chemicals or radiation.
So, if humans make it to the stars, part of the success of this feat may be based on learning from the tiny, eight-legged endurance specialists who inhabit our backyards.
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