Fungal spore survival in stratospheric extreme conditions
PI: Jérôme Kasparian
Collaborators: Katia Gindro, Agroscope
Funding: DIP; FNS request under evaluation
Dates: 2023 --
Description:
Fungi are ubiquitous. From a pathological perspective, this implies their constant presence and readiness to colonize substrates when climatic conditions become favorable. 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. Furthermore, preliminary in-situ measurements suggest that some spores indeed survive in the stratosphere.
We investigate the density, taxonomy, and viability of fungal spores in the Earth stratosphere, between 12.000 and 35.000 m 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 laboratory for cellular and molecular analysis. More specifically, we analyze cultivable fungi in the stratospheric samples. Furthermore, given that cultivable fungi likely represent only a small fraction of the total fungal diversity at altitude, we will also assess the full fungal biodiversity of the stratosphere using environmental DNA (eDNA) and metabarcoding. This technique involves detecting the trace DNA left by each fungal species within a given environment. This makes it possible to highlight non-cultivable fungi as well as obligate biotrophic oomycetes.
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. Such abilities are key to develop in potentially extreme conditions of exoplanets.
These findings will 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 in remote worlds.
Positions:
- One PhD student (Sara Leoni)
- One apprentice (Océane Devisme)