Discovery explains how unkillable tardigrades survive without water

Scientists studying the biology of the tardigrade have filled in important new details around how the tiny aquatic creature can survive the harshest of conditions. The discovery centers on a newfound mechanism that kicks into gear as dehydration sets in, protecting cells from death due to mechanical stress.

Also known as water bears, microscopic tardigrades are famed for their hardiness in all kinds of extreme settings, and the more we learn about them, the more impressive their survival skills seem to be.

Studies have detailed how tardigrades use DNA clouds and fluorescent shields to protect themselves from different kinds of radiation. They are also known to enter a state of suspended animation to survive boiling and freezing temperatures and the crushing pressures at the bottom of the ocean. Research has even suggested that they survived a crash-landing on the Moon, and that they may even live to see our Sun die.

Living without water is just one of the skills in the tardigrade toolkit, and scientists at Japan’s University of Tokyo have gained a new understanding of the biological process behind it. The team was investigating cytoplasmic-abundant heat soluble (CAHS) proteins, which recent research has shown become activated in tardigrades when dehydration sets in.

In exploring their role further, the team found that in dehydrated tardigrade cells, the proteins come together to form gel-like networks of protective filaments that help the cells keep their shape as their water content dries up. When the tardigrade cells were rehydrated the process is reversed, with the filaments slowly receding to avoid causing mechanical stress on the cell.

“Although water is essential to all life we know of, some tardigrades can live without it potentially for decades,” said study author Takekazu Kunieda. “The trick is in how their cells deal with this stress during the process of dehydration. It’s thought that as water leaves a cell, some kind of protein must help the cell maintain physical strength to avoid collapsing in on itself. After testing several different kinds, we have found that CAHS proteins, unique to tardigrades, are responsible for protecting their cells against dehydration.”

While these initial experiments focused on the function of CAHS proteins in dehydrated tardigrade cells, the team showed that they performed a similar but limited function when isolated and studied in human and insect cells. This kind of research could lead to new technologies for the dry preservation of cells or even organisms, which could mean medicines last longer on the shelf, for example, or organs survive longer outside the body before transplantation.

“Everything about tardigrades is fascinating” said Kunieda. “The extreme range of environments some species can survive leads us to explore never-before-seen mechanisms and structures. For a biologist, this field is a gold mine.”

The research was published in the journal PLOS Biology.

Source: University of Tokyo