Using Water Bears to Investigate Adaptations to Extreme Stresses

Certain animals can survive environmental extremes that are beyond those at which purified DNA, protein, and membranes typically degrade; suggesting that mechanisms exist that protect and/or rapidly repair multiple cellular components. Some protectants have been identified, but the mechanisms that can allow animals to survive such extremes are in general not yet well understood, despite being of wide interest. The long-term goal of this work is to contribute to understanding the mechanisms by which animals and animal tissues can survive extremes. This project addresses this issue using tardigrades, which are microscopic, 8-legged invertebrates that can survive a remarkable range of environmental extremes: desiccation for years, ionizing radiation 1000 times what humans can survive, temperatures from below 1 degree Kelvin to more than 150 degrees Celsius, and extremes of pressure including even the vacuum of space. The project also involves several efforts with potential to have broader impacts, including making educational materials for children and teachers, contributing to museum exhibits and events, providing images and videos to television and print journalists and for textbooks, and sharing of newly developed methods with other scientists seeking to make use of this emerging model system.

Tardigrades and other organisms have acquired certain genes by horizontal gene transfer from other organisms including bacteria. Recent studies have revealed the roles of certain horizontally transferred genes in the ability of tardigrades to survive some extreme conditions. This project will more thoroughly identify mechanisms that contribute to survival of extreme conditions by examining functional roles for a set of horizontally transferred genes whose expression is induced by an environmental extreme. The hypothesis that products of certain foreign genes can perform key biochemical functions under extreme conditions will be tested, and the mechanisms by which these genes entered tardigrade genomes will be investigated. Methods to be shared through this project include lab culture methods, methods for examining tardigrade gene expression and disrupting gene functions, and methods newly developed in the course of the research. The research in this project and its efforts to make tardigrades easier for other scientists to study may contribute, in the long run, toward suggesting new avenues for the development of protectants for biomaterials.