For the first time, researchers have successfully isolated both animal and human DNA from the air, paving the way for new and better ways to monitor animals noninvasively.
The study, published March 31 in PeerJ, provides the first evidence that environmental DNA, or eDNA, can shed from animal cells and persist in the air long enough to be collected and analyzed.
When cells degrade and die, their DNA is shed into the environment, allowing researchers to collect and analyze the DNA without having access to the organism itself. This is useful in tracking animals as they move through different environments. It's also a less invasive method from a conservation standpoint.
"The world is really an ocean of DNA. It's in the water, the soil, and now we know it's in the air," first author Elizabeth Clare said in an explanatory video accompanying the study. "This is a huge source of information for us to learn about the planet."
Clare, a molecular ecologist at Queen Mary University of London, explained in an interview with The Academic Times that eDNA is not a new discovery, but it is currently collected mainly from aquatic environments, not the air.
"Environmental DNA is a tool that is now very, very common in scientific literature and has made its way into a lot of regulatory bodies and even commercial industries," she said. "It's a very common approach to monitoring fish and other aquatic things, and even mammals, through runoff from the shoreline into the water we can detect."
However, there is no scientific literature demonstrating that eDNA can be isolated from the air, though there have been a few attempts made by students, including a high school science-fair project in Japan. But those attempts have not been extensively documented or peer reviewed.
Clare and her colleagues believed that it would be possible to collect and sample eDNA from the air, but they needed to develop an ideal system to put this hypothesis to the test. So they turned to a bizarre creature: the naked mole rat.
Clare explained that the naked mole rat was an ideal subject for the study because her co-author Chris Faulkes had already established indoor colonies of the rats as part of his other research, making them easy to study during nationwide COVID-19 lockdowns in the U.K. Using a hairless animal also eliminated the possibility of hair contaminating the samples.
"We're really in this trying to maximize the chance of success," Clare said. "So we have an established colony in an established room that is going to be contaminated with DNA [and] is likely to give us a good result."
A good result is exactly what the researchers got. By filtering air through a sieve smaller than a molecule of DNA and then amplifying the collected DNA through a polymerase chain reaction, the team collected enough DNA to sequence using classical genetic methods.
As hypothesized, their samples contained naked mole rat DNA. However, the researchers were surprised to also find human DNA in their samples, indicating that DNA from the animals' caretakers was also able to persist in the air.
This method of collecting DNA has immediate ecological implications for the surveillance of animal species, especially in hard-to-reach areas, such as in caves or underground. The researchers are already partnering with industries and charitable organizations to bring these applications to life, including NatureMetrics, an eDNA-monitoring company.
However, the discovery of human DNA within the samples also presents a flood of alternative applications yet to be explored.
"What started off as an attempt to see if this approach could be used for ecological assessments has now become much more, with potential applications in forensics, anthropology and even medicine," Clare said.
However, before these applications can be brought to fruition, the techniques need to be further refined. This study proves the concept in an ideal environment, but much remains to be learned about the full scope of its application.
"We really need to expand the study to consider all the factors which might help preserve or degrade that air DNA. That will help us understand its potential as a tool," Clare said in the video. "I really hope other people will go out and try this — help us narrow down the methods that are going to work and the conditions that are going to make this a really useful tool. This is [a] really exciting new development. I look forward to seeing what comes next."
The study, "eDNAir: proof of concept that animal DNA can be collected from air sampling," published March 31 in PeerJ, was authored by Elizabeth L. Clare, Chloe Economou, Chris G. Faulkes, James D. Gilbert, Frances Bennett, Rosie Drinkwater and Joanne E. Littlefair, Queen Mary University of London.