Tardigrade observed using a confocal fluorescent microscope. The tardigrade was overexposed to 5-MF, a cysteine selective fluorescent probe, that allows for visualization of internal organs. Credit: Smythers et al., 2024, PLOS ONE, CC-BY 4.0
Key points:
- Researchers exposed tardigrades, microscopic animals also called “water bears”, to freezing temperatures or high levels of hydrogen peroxide, salt, or sugar to trigger dormancy.
- During these experiments, they found that water bears use a molecular sensor—based on the amino acid cysteine—to detect harmful conditions and signal the need for dormancy.
- These results uncovered the regulatory mechanism that contributes to water bears’ hardiness and ability to survive in ever-changing environments.
Tardigrades, also called “water bears” are microscopic animals that can withstand extreme conditions including freezing temperatures, radiation, and environments without oxygen or water. A new study, published in PLOS One, reveals how water bears are able to go dormant and enter a tun state to survive these conditions.
Researchers exposed water bears to freezing temperatures or high levels of hydrogen peroxide, salt, or sugar to trigger dormancy. As a response to these harmful conditions, water bears’ bodies became dehydrated, their eight legs retracted, their metabolism slowed, and their cells produced damaging oxygen free radicals.
During these experiments, researchers found that water bears use a molecular sensor – based on the amino acid cysteine. The sensor detects harmful conditions as it is oxidized by oxygen free radicals and signals the animals to enter the tun state. Once conditions improve, the free radicals disappear and the water bears emerge from dormancy.
To confirm the role of cysteine, the team applied chemicals to block cysteine and determined that the water bears were no longer able to detect free radicals or go dormant, meaning cysteine is key for the dormancy response to multiple stressors.
For the first time, these results uncover the regulatory mechanism that allows water bears to enter and leave a state of dormancy and survive in ever-changing environments.