Scientists have sucked animal DNA out of thin air for the first time
On a dreary winter day in December 2020, conservationist Elizabeth Clare strolled through Hamerton Zoo in England brandishing a small vacuum pump. She paused outside the animal enclosures, holding up a flexible tube attached to the machine. His mission: to suck up animal DNA from nothing.
The ability to detect the airborne genetic material of animals has been on scientists’ wish lists for more than a decade. DNA taken from water has been used to track aquatic species, including salmon and sharks (SN: 07/05/18). Scientists knew they could use environmental DNA, or eDNA, in the air to monitor terrestrial species — if only they could trap it. Now researchers have done just that using vacuum cleaners, two independent groups report Jan. 6 in current biology.
“It’s such a crazy idea,” says Clare, of York University in Toronto. “We suck DNA from the sky.”
The idea came to Clare, who did the work at Queen Mary University of London, during a previous experiment in which she sampled the air outside naked mole-rat burrows. At the zoo, Clare and her colleagues ran the vacuum pump for half-hour sessions in and around animal enclosures, collecting 72 samples from 20 sites. Then the team took the material trapped in the pump filter back to the lab for analysis.
Meanwhile, another team from the University of Copenhagen was unknowingly pursuing the same idea. Biologist Kristine Bohmann and her colleagues sought to trap airborne DNA at Copenhagen Zoo using tiny fans similar to those that cool computers. The team also experienced the void. By deploying their contraptions between 30 minutes and 30 hours in the tropical house, stables and outdoors, the researchers found that the fan method and the vacuum method collected a large amount of animal DNA.
“It was so much fun,” says Bohmann. “It felt like we could just play and be creative.”
To test the technique, the two teams used a zoo for its list of animals. Air in nature could harbor DNA from unpredictable places, but in zoos, researchers could cross-reference DNA captured from the air with animals listed in exhibits. This allowed scientists to confirm the source of the DNA and see the distance traveled between the enclosures.
Bohmann and his colleagues identified 49 different vertebrate species in Copenhagen Zoo. They detected animals living in the sampled enclosures, such as okapis (Okapia johnstoni) in the stables and a land boa from Dumeril (Acrantophis dumerili) in the rainforest house. But the researchers also discovered mammals and birds from surrounding exhibits as well as fish used as food. “It was quite surprising,” says Bohmann.
At Hamerton Zoo, Clare’s team identified 25 different species, including not only targeted zoo residents, but unexpected species as well. In the dingo enclosure, the team detected DNA from meerkats (suricata suricatta) that live 245 meters away.
Strangers at the zoo also appeared in each team’s results. Clare’s team detected the European hedgehog (Erinaceus europaeus), which is endangered in England, while Bohmann’s group discovered domestic mice and dogs. They also picked up whiffs of human DNA.
Sucking DNA from the air could be a non-invasive way to identify where endangered species are by detecting their genetic fingerprints, says Bohmann. The method would be an upgrade to camera traps, which only work when creatures are walking around, she says.
Neither team was aware that the other was working on the same concept. They got in touch after seeing an early draft of each other’s studies on a preprint server. Clare describes it as “the most enormous scientific coincidence” in either of their lives. The teams chose to publish their studies together to corroborate each other’s findings and foster adoption of their emerging ideas.
How this proof-of-concept technology will translate to the field is unclear. Airborne eDNA in nature is more dispersed and detection can be affected by environmental factors such as weather and wind. But just as aquatic eDNA has advanced over the past decade, so too will airborne eDNA, Clare says. “I’m really looking forward to seeing other people come out and use the technique.”