All things fungal are popular again, what with the release of the second series of The Last of Us, the fungus-ridden zombie post-apocalyptic drama show based on the celebrated video game. But while viewers across the land sit and watch this misnamed show (seriously, for the “last” of us, there are certainly a lot of people knocking around. It’s more like The Most of Us), little do they know that fungal spores are traveling great distances miles above their heads.
The spores were picked up by scientists as they drifted in the stratosphere, which typically has harsh conditions that would kill most other organisms. However, when the researchers brought the spores back to their lab, they were able to culture some specimens that are known to cause infections in humans and plants.
The survival of microorganisms, like bacteria and fungi, in the Earth’s stratosphere has become increasingly interesting for scientists in recent years. This is a known an inhospitable environment, boasting all sorts of life-ending factors such as low temperatures, higher levels of ultraviolet and ionizing radiation, lower atmospheric pressure, and significant nutrient scarcity. By identifying the kinds of microorganisms that can survive in these conditions, as well as figuring out how they get up there – reaching heights well above that of even commercial aircraft – scientists can learn a great deal about various issues related to climate change and astrobiology.
In addition, they can also learn more about how potentially dangerous pathogenic organisms spread across the world, which in turn could help establish ways to combat emerging diseases. That was the driving force behind this latest research.
Spores are essentially the seeds of fungi. They are released through various mechanisms depending on the fungal species and are dispersed on the air, which can carry them great distances. They are incredibly tough. Depending on the chemical and structural nature of their walls, some are able to survive extreme conditions such as remarkably high temperatures or exposure to UV radiation. In fact, the spores of Botrytis cinerea (conidia), a fungal pathogen responsible for gray mold disease, can be dry stored at -80°C (-112°F) for years and still be capable of germinating.
This potent survivability suggests fungal spores can likely endure the harsh conditions in the stratosphere, so a team of researchers led by Jérôme Kasparian at the University of Geneva’s Institute for Environmental Science and Katia Gindro at Agroscope, Switzerland’s agricultural research center, designed a cheap sampling device to examine their diversity.
The device consists of a sealed polystyrene box that has ports at the top and bottom. These ports allow for air to circulate inside the box. As air flows into the box, a rotating arm spins to collect samples from the air. The arm has four sticks attached to it, each coated with petroleum jelly (to serve as an adhesive for airborne microorganisms).
The box remains sealed as it rises into the air, carried by a meteorologic balloon. Once it reaches 12,000 meters (39,370 feet), the ports are opened by mobile covers driven by servomotors controlled by a system connected to a high-pressure pressure sensor. When the balloon eventually bursts at around 35,000 meters (114,829 feet), it parachutes back to Earth. The cover closes again once it reaches 12,000 meters.
The box has been fitted with a GPS transmitter, so it can be easily collected once it arrives back on the ground.
The researchers have now carried out five test flights, between October 2023 and June 2024, allowing them to validate and optimize the device and to assess the sampling conditions.
Based on DNA sequencing analysis, the team identified 235 genera of fungi, including some that are pathogenic to plants and humans. These included species that infect blackberries and carrots in the US and Japan, as well as the species Naganishia albida, which causes sickness in immunocompromised people. During their lab work, the team was also able to revive and culture around 15 species of spores, which also included some plant pathogens. Other species did not survive the extreme conditions in the stratosphere, so could not be revived.
The research not only proves the effectiveness of the team’s low-cost sampling device but also demonstrates the need for monitoring the atmosphere for traveling fungal spores. Keeping track of their biodiversity and seasonal variations may be an important step in identifying potential future contaminations.
The study was presented at the European Geosciences Union General Assembly 2025.
Source Link: Pathogenic Fungal Spores Found Surviving Miles Above Our Heads In Earth's Stratosphere
