Fungal spore survival in stratospheric extreme conditions
Fungi are ubiquitous. While their presence at low and medium altitudes up to 3000-5000 m is relatively well known, data about spore occurrences in the stratosphere is very sparse. Still, laboratory experiments have suggested that they could withstand the harsh stratospheric conditions including temperatures down to -63°C and intense UV irradiation.
In collaboration with (Agroscope), we investigate the presence and viability of fungal spores in the Earth stratosphere, between 12 and 35 km altitude, as well as the dynamics of their transport to the stratosphere, via either diffusion or injection events caused by wildfires or large volcanic eruptions.
We have developed dedicated sampling systems carried by regular radiosonding balloons up to 35 km altitude. They open and start sampling spores with glycerine-enducted spinning sticks based on real-time altitude measurements, while a regular radiosonde attached to the setup records and transmits the ambient conditions as well as the device position and altitude based on GPS.
The samples are recovered after landing and returned to the Agroscope 
Survival analysis provide valuable insights into the resilience of each species under extreme stratospheric conditions, including their ability to withstand low temperatures, UV radiation, and prolonged desiccation.
These findings also provide a highly valuable understanding of the long-distance dissemination risks posed by these fungi in both natural and agricultural ecosystems, particularly in the context of climate change and stratospheric dispersal, but also in the context of evolution in harsh conditions that may be encountered on exoplanets.