There's a worm that can live a mile underground; this 'Devil Worm' was found in an aquifer and is the deepest animal that's been found living beneath the surface of the Earth. Researchers at American University have now sequenced the genome of this strange creature, which can survive in the harsh conditions found that far underground. This data, which has been reported in Nature Communications, may help us gain insights for the survival of our own species in a changing environment.
The worm was identified in 2008 by scientists Gaetan Borgonie and Tullis Onstott during their studies of subterranean bacterial colonies in the gold mines of South Africa. They were shocked to discover a multicellular animal in a place where they thought only microbes would be able to thrive; oxygen levels were low, methane levels were high, and it was very hot. They named the organism for Mephistopheles, dubbing it Halicephalobus mephisto.
This is the first time we've learned the genetic sequence of a subterranean animal. It can help show us how life might adapt in the extreme environments of Earth, or beyond, noted the research leader, John Bracht, an assistant professor of biology at American University who led the genome sequencing project.
The animal's genome carries many genes that code for proteins that are activated by stress, heat shock proteins (Hsps), specifically, many Hsp70 genes. Few other worm species carry this many Hsp70 genes, which are well known to be essential for life. They can help cells survive heat damage by restoring cellular health. Many Hsp70 genes in the Devil Worm genome are repeated. The animal also carries many copies of AIG1 genes, which are known to aid cell survival in animals and plants.
Bracht suggested that these gene copies indicate that the worm has evolved to adapt to its environment. "The Devil Worm can't run away; it's underground," Bracht explained. "It has no choice but to adapt or die. We propose that when an animal cannot escape intense heat, it starts making additional copies of these two genes to survive."
Bracht's team has also found that in bivalves (mollusks like mussels and oysters) there were many copies of Hsp70 and AIG1 genes. These animals are adapted to heat too, suggesting that the genetic pattern may help animals withstand the stresses of heat in their environments.
Since the discovery of the Devil Worm, Bracht and others have been studying it, in part to understand how life in extraterrestrial may be surviving. Worms are a good model to study evolutionary adaptation; they live in many different kinds of places and are plentiful.
"Part of this work entails looking for 'biosignatures' of life--stable chemical clues left behind by living things. We focus on a ubiquitous biosignature of organic life--genomic DNA--obtained from an animal that has adapted to an environment once considered uninhabitable to complex life: the deep terrestrial subsurface," Bracht explained. "It is work that might prompt us to broaden the search for extraterrestrial life to uninhabitable exoplanets' deep subterrestrial regions."
Bracht's team wants to know more about how Hsp70 is working in the worm, and how it may be responding to stress. They are also interested in transferring the gene to other types of worms to see whether it enables them to withstand heat.