S.Years ago, Sandeep Eswarappa was filming the documentary film show cosmos and was immediately immersed in the subject of the episode: tardigrades. It was great enough that the pinhead-sized animals could endure extreme environments on earth and in space. But it was the fact that these organisms, also known as water bears, survived all five of the mass extinctions on Earth that caught Eswarappa’s attention, he says The scientist. “I then decided that tardigrades would be one of my projects when I returned to India to open my own laboratory.”
At the time he saw them cosmos Eswarappa was a postdoctoral fellow in cell biology at Cleveland Clinic, studying cancer and other pathologies associated with the abnormal growth of blood vessels. About a year later, in 2015, he was hired to start his own group at the Indian Science Institute in Bangalore, and he recruited PhD student Harikumar Suma to help him start a tardigrade project. Fascinated, Suma and several other students at the lab began combing the institute’s crevices for water bears to study, and eventually found some in the moss growing on a concrete wall.
Suma brought the moss back to the lab and gently patted it on the side of a Petri dish to remove and collect the tardigrades for examination under a microscope. Like other tardigrades, they appeared as 600 nanometer long, reddish-brown bear-like creatures with four pairs of legs and tiny, Y-shaped claws at the tips. However, when the researchers sequenced the tardigrade genomes, they found that the sequences did not correspond to any previously identified species; This was an entirely new species of the genus Paramacrobiotus. This led to a challenge in cultivating the water bears in the laboratory, because “we didn’t know what they feed on and what temperature they need to live. . . its life cycle, ”says Suma, now a project assistant at the Leibniz Institute for Natural Product Research and Infection Biology in Germany The scientist. “There has been a lot of trial and error and a lot of tardigrades have been lost.”
This recently identified species of tardigrade glows blue under UV light.
With kind permission of SANDEEP ESWARAPPA
However, after a month, Suma found the ideal place to grow the tardigrades and began to study their resilience to various environmental stressors. He and Eswarappa were particularly curious about the animals’ resistance to ultraviolet (UV) radiation. The tardigrades were placed under a germicidal UV lamp – an exposure that would kill most microorganisms – for 15 minutes and were left intact. Curious to see if they could give the UV protection C. elegans and another species of water bear, the researchers grind up the new tardigrade to make a paste containing the mysterious UV-resistant substance that they could apply to the other creatures. They found that the paste fluoresced under UV light.
Other animals, such as comb jellies and corals, also fluoresce and can do so as protection against UV light, as fluorescent molecules absorb light of higher wavelengths than they emit and prevent the harmful radiation from damaging the animals’ cells. The results from Suma and Eswarappa suggested that the same could be true of the new species of water bear. Tardigrades that contained a higher concentration of fluorescent molecules showed better UV exposure than those with less. And when the team was bathing C. elegans and the UV-resistant tardigrade Hypsibius exemplaris They survived in the extracted fluorescent molecules and exposure of the animals to UV light. “It was like putting a sunscreen on your skin,” says Eswarappa.
With the results, Eswarappa and Suma join a growing group of scientists studying tardigrade tolerance to extreme environments, says Nadja Møbjerg, a cell biologist at the University of Copenhagen and an expert on water bear research. “The field has received a lot of attention in recent years,” she says. “It’s actually an expanding field.”
Some of the attention could be due to the popularization of tardigrade science by people like Neil deGrasse Tyson cosmos and the stories of journalists in the media. James Kadonaga, a molecular biologist at the University of California at San Diego, actually fell into tardigrade research after reading an article about the animals in Chemical & Engineering News. The piece, published in 2016, explained Takuma Hashimoto’s work on sequencing the entire genome of the most stress-resistant tardigrade species of the time. Ramazzottius varieornatus. Based on the genetic analysis, the team identified a protein called Dsup, or Damage Suppressor, that was responsible for making the tardigrade tolerant of X-rays and other stressors. When added to human cell cultures, the protein blocked x-ray and oxidation damage to DNA.
Kadonaga, an expert on chromatin, was particularly interested in mentioning the article that dsup colocalizes with nuclear DNA in tardigrade cells. He looked up the sequence of the Dsup protein in Hashimoto’s original paper and was surprised by what he saw. “It looked a bit like a chromatin protein,” says Kadonaga The scientist. Working with student Carolina Chavez, Kadonaga discovered that Dsup binds to nucleosomes, structures made up of roughly two turns of DNA wrapped around a set of eight histone proteins. Dsup can form a kind of “protective cloud” of protein around the chromatin and protect the DNA from the hydroxyl radicals that arise when X-rays hit cells, explains Kadonaga. The team also showed that dsup wasn’t the only protective protein in the tardigrade arsenal. H. exemplaris has an ortholog that seems to work in the same way.
Studies like those by Kadonaga and Eswarappa could have practical applications, the researchers say. For example, Dsup or other related proteins could be used to extend the life of cell lines designed to make proteins or T cells designed to fight cancer. “You may be able to make cells that are tougher, more robust, and possibly last longer,” says Kadonaga. Tardigrades’ newly discovered fluorescent molecules could now be used in sunscreens or UV-resistant glasses, says Eswarappa.
A lot of water bear research also deals with basic research questions in areas like evolutionary biology and genetics, Møbjerg says. Her way into the field led through her father Reinhardt Kristensen, a world expert on tardigrades. When she watched him study tardigrades, she was fascinated by them. When she received a tenure, she began her research on anatomy, phylogeny, and the animal’s ability to tolerate warming air temperatures and changing salt levels in seawater. When she worked with tardigrades found in gutters around Copenhagen, she found that heating their water in the laboratory made them “feel less good”. They didn’t have the usual fidgeting of legs and bodies, she says.
This observation started her team’s work on the animal’s response to climate change, an issue other teams have also worked on. In warmer temperatures, it could be the Achilles heel of the tardigrades, she says. “They tolerate warming temperatures less well than other extremes.”
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