Water Bear genome shows ‘stolen DNA’ in surprising amounts. Water bears, also referred to as tardigrades in scientific terms, are microscopic creatures that have been the object of several scientific research projects due to their unique abilities. Tardigrades seem to be able to survive in the most dire conditions such as freezing, radiation bombardment, complete dehydration and even within the vacuum of deep space.
But a new analysis of tardigrades by a group of researchers led by biologist Thomas Boothby at the University of North Carolina has focused on the tardigrade genome and has revealed that 17.5 percent of this genome actually descends from other organisms such as bacteria, fungi, plants and viruses. It seems that these genes were assimilated by the tardigrade DNA through a process known as horizontal gene transfer, which is common for single-celled organisms but extremely rare for animals.
The researchers isolated non-animal genes contained in the tardigrade gene sequence and then compared these non-animal genes with genes pertaining from other sequences organisms. Approximately 17.5 percent of the genes analyzed in the tardigrade seemed to closely resemble genes of non-animal origin, from organisms like plants and bacteria. This is unique in that it is the first time scientists have found an animal with a genome that is on-sixth of non-animal provenance.
Biologist Bob Goldstein, who collaborated on the study, explained that researchers can’t be sure which the exact species that contributed with their DNA to that of the tardigrade were, partially because some of those species’ genomes may have not yet sequenced and documented by scientists.
What might be the most interesting question worth asking is how did the tardigrade aquire such an eclectic genome? Researchers have speculated that its complex genome might be explained by the way the creature reacts to fear and stress. As tardigrades usually live in wet moss, one of their exposures to danger could include their need to endure desiccation, which means that they would need to dry out and, because of that process, their DNA would break.
However, when water would return to the area where the dried tardigrades were, they would rehydrate and continue to function. It is during this process of rehydration that their cell walls would become porous and fragments of DNA from desiccated organisms around them could enter their bodies and merge with the tardigrade’s revitalizing DNA.
Researchers have found that every time a tardigrade survives such a life-threatening form of stress, it picks up more genes in order to help itself recover from the ill effects of that stress.
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