Flying skydivers leads geneticist Clemson to develop a system to detect DNA in the sky

July 5, 2023July 5, 2023

As she flew through a Saharan dust plume above Anderson while piloting skydivers to their jump altitude, Clemson University geneticist and licensed commercial pilot Kimberly Mtris saw a research opportunity literally before her eyes.

The atmosphere was saturated with particulate matter as transcontinental clouds of dust and sand swirled through the air, creating a visually stunning spectacle.

At altitude, I could see dust particles making their way out of Africa in these strong air currents, said Mtris, a former Clemson student who has been a faculty member in the Department of Genetics and Biochemistry since 2019. I mused. about what genetic material was there and in the air I fly every day. He then decided to conduct research to unravel the mysteries that lay above.

Long story

Atmospheric biology has a long and rich history, since the 1800s scientists have studied the microorganisms in airborne atmospheric dust.

Airplanes in particular are useful for covering long distances at selected altitudes in short periods, Mtris said. As early as 1921, airplanes were being used to capture biological material in the United States for plant pathogen monitoring. In the 1930s, people like Fred Meier and Charles Lindbergh had reported collections of microorganisms from the United States and the Arctic atmosphere by plane.

To conduct his research, Mtris wanted an instrument that was cheap, sterilizable, and could be precisely controlled to sample bioaerosols directly from the atmosphere using an aeroplane. Such an instrument didn’t exist, so she and her husband, Jeremy Mtris, developed one that features full-flow active filtration of a quantifiable and controllable volume of air and a high-integrity chamber to protect the sample from leaking or contaminations.

The probe can be mounted on an aircraft wing strut to sample only the free airflow ahead of the wing’s leading edge. It is controlled by the operator via a vacuum pump and manifold inside the aircraft cabin.

Using an aerial survey grid developed by the researchers, Mtris flew over an area of ​​more than 4,500 acres in northwest South Carolina and northeast Georgia.

The area is characterized by numerous poultry and livestock farms; agricultural fields and forests; industrial buildings such as sewage treatment plants, hospitals and clinics; and other urban development activities. Ground-level emission patterns were visible from the aircraft at all flight altitudes.

The researchers conducted flights in May and June 2022 and collected samples at three altitudes of 1,800, 4,500 and 8,500 feet above mean sea level.

After collecting the samples, Mtris used high-throughput metagenomics for sequence identification.

More than 50 types

The study, recently published in the journal PeerJ life and environment, discovered the widespread and heterogeneous presence of prokaryotic and eukaryotic environmental DNA in the atmosphere, reaching thousands of meters into the planetary boundary layer of the lower troposphere.

Over 50 types of airborne bacteria, including pathogens, have been sequenced. Common plant allergens from grasses, weeds, and trees and weeds have also been found to have antimicrobial and anti-inflammatory properties.

Surprisingly, the researchers found animal bioaerosols at high altitudes, including chicken, cow and human DNA detected at all altitudes. DNA has also been recovered from bacteria previously undocumented in the lower troposphere but reported in other extreme environments such as deep-sea sediments and the International Space Station.

Human activities such as waste disposal and treatment, agriculture and industry, as well as natural processes such as pollination and evapotranspiration can release bioaerosols with DNA and RNA into the atmosphere, propelling them to new locations.

Mtris pointed out the power of atmospheric circulation in transporting these bioaerosols.

This environmental DNA or RNA can be lifted, transported and deposited elsewhere by atmospheric mixing, lifting action, buoyancy and other air biogeography processes, potentially leading to biological consequences such as gene flow and hybridization.

Microorganisms and pollen in the air can act as nuclei for ice and cloud formation, affecting our global climate.

We breathe and ultimately exist in a mighty ocean of air, Mtris said. The global pandemic is a recent example that has brought this reality to the forefront of society. Atmospheric environmental genomics is an exciting and emerging field with applications that we are just starting to explore, and the sky is not the limit!

The detailed results can be found in the paper titled Aircraft surveys for air eDNA: probing biodiversity in the sky.