Unravelling the mysteries of the devil worm.

Prof. John Bracht, American University

This infernal nematode otherwise known as the devil worm (Halicephalobus mephisto) lives more than 1.50 km below the Earth's surface and can survive extremely harsh conditions.

A team of scientists has sequenced its genome, offering clues as to how it adapts to incredibly extreme environments and also opens new doors in the search for extraterrestrial life. 

This peculiar nematode was not discovered until 2008, in a South African gold mine and was immediately named as the only living species found so deep under the Earth’s surface. After all, who else could we find living in the intense heat and crushing pressure of such depths? 

With the sequencing of its genome, scientists have extracted some of the secrets of the devil worm. For example, to maintain its slender half-millimetre figure, it fearlessly bites bacteria. And since it has probably been under our feet for thousands of years, the creature has had plenty of time to evolve in this inhospitable habitat. Its genome shows many adaptations designed to cope with the high heat where it lives.

For example, this extremophile has duplicated a gene that repairs fire damage until it has made  70 copies of the gene. It has multiple copies of a second protective gene, leading scientists to speculate that the devil worm wrapped itself in armour to survive the conditions around it.

The sequence revealed that the genome encodes an unusually large amount of thermal shock proteins known as Hsp70, something to note, because many species of nematodes whose genomes are sequenced do not reveal such a large amount. Hsp70 is a well-studied gene that exists in all life forms and restores cell health due to heat damage.

The worm also has spare copies of a gene called AIG1, which is related to cell survival in plants and animals.

By scanning other genomes, experts identified other cases in which the same gene families expand.  

"It has no choice but to adapt or die. We propose that when an animal cannot escape the intense heat, it begins to make additional copies of these two genes to survive," the authors stated in a study published in the journal Nature.

The devil worm has become the first genetically mapped underground creature, giving researchers hope that studying other organisms will conclude with equally unusual and inspiring results.

Who knows if the knowledge the devil worm has just revealed can teach us anything about living with a demon we know well: climate change.

Reference: Weinstein, DJ, Allen S, Lau M, Erasmus M, Asalone KC, Walters-Conte K, Deikus G, Sebra R, Borgonie G, van Heerden E, Onstott TC, Bracht, JR. The genome of a subterrestrial nematode reveals an evolutionary strategy for adaptation to heat. Nature Communications. DOI: 10.1038/s41467-019-13245-8 / Megan N. Guerin et al. Stress Adapted Mollusca and Nematoda Exhibit Convergently Expanded Hsp70 and AIG1 Gene Families, Journal of Molecular Evolution (2019). DOI: 10.1007/s00239-019-09900-9



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