In November 2015, Proceedings of the National Academy of Sciences published a paper reporting an incredible feat achieved by the microscopic tardigrade species Hypsibius dujardini. Already known for their incredible resilience to the elements, these tardigrades, reportedly, incorporated 17.5 percent foreign DNA into their genome.
However, the notion has been challenged by U.K. researchers, who published a new paper in Proceedings of the National Academy of Sciences last week.
“We independently sequenced the genome of H. dujardini and detected a low level of horizontal gene transfer,” the researchers wrote, noting that the previous study’s results were prompted by a failure to eliminate contaminants.
Tardigrades—also known as water bears— can survive desiccation, a process that leads to extreme dryness. Thomas Boothby and Bob Goldstein, both of the University of North Carolina at Chapel Hill (UNC) and authors of the November study, postulated that the drying out process was integral to the acquirement of foreign DNA. As Boothby explained previously to R&D Magazine, the DNA fragments may break apart as the animal’s cells dry out. Rehydration, however, could cause the cell’s plasma membrane to become leaky, temporarily allowing the transfer of DNA between the environment and the animal’s cells.
“Our assembly of the H. dujardini genome conflicts with the published UNC draft genome, despite being from the same original stock culture” the U.K. researchers wrote.
They found that less than 1 percent of the tardigrades’ genes were borrowed from other species.
“What would in decades past have taken many months to sort out became the focus of experts around the world and has been swiftly resolved,” said study co-author Mark Blaxter, of the University of Edinburgh. “We hope this paper will finally correct the scientific record. Tardigrades are amazing organisms, but these suggestions about their DNA were a step too far, even for their eight legs.”
Speculation surrounding Boothby and Goldstein’s work started appearing in early December, with various media outlets citing Blaxter and the University of Edinburgh’s follow-up study. A preprint paper was made available Dec. 1, 2015 to the public on bioRxiv server.
Boothby and Goldstein commented on the preprint paper. While they said they would undertake their own further analyses, they wrote “We appreciate that bioRxiv preprint server is a valuable way to move science like this forward without delay.”
Boothby did not respond to R&D Magazine’s request for a comment.
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