Fungal Proteins in the Sky: A New Discovery in How Rain Might Form
A study published in Science Advances reports a significant discovery: ice-nucleating proteins (INpros) produced by fungi. These proteins, primarily from the Fusarium and Mortierella genera, could play a previously unknown role in the Earth's water cycle.
These fungal proteins are secreted into the soil, are water-soluble, and can initiate ice formation in clouds at temperatures as high as -5°C. This is notably warmer than the temperatures typically required by other atmospheric particles like mineral dust or soot.
Background: The Need for a "Seed"
For precipitation like rain or snow to form, supercooled water droplets in clouds require a particle, or "seed," to initiate ice crystallization. This process is known as ice nucleation.
Certain bacteria, such as Pseudomonas syringae, are known to produce INpros that facilitate this process at relatively warm temperatures, around -2°C. The newly identified fungal INpros are structurally different from their bacterial counterparts and are secreted externally into the environment.
Mechanism and Ecological Implications
The research describes a potential bio-precipitation cycle. In this proposed cycle:
- Fungal proteins from forest soil are lofted into the atmosphere by wind.
- In clouds, they seed ice crystal formation.
- This contributes to rainfall, which subsequently returns to the soil and supports fungal growth.
Genetic analysis indicates that fungi in the Mortierellaceae family acquired the genes for these proteins via horizontal gene transfer from bacteria millions of years ago. Researchers suggest the proteins may aid fungal survival by directing moisture, providing frost protection, or aiding spore dispersal.
The study's authors note a potential environmental concern: widespread deforestation could disrupt this proposed biological rainfall mechanism by removing the source of these proteins.
Potential Applications
Beyond the natural cycle, these proteins have captured interest for their practical potential. They are proposed as a biodegradable alternative to substances like silver iodide for cloud-seeding programs. Such programs aim to induce precipitation or protect crops from frost.
Other potential applications mentioned in the research include use in snowmaking, food preservation, and advanced cooling systems.
Source: This article is a republication from The Conversation, authored by Diana R. Andrade-Linares, a Postdoctoral Fellow in Microbial Ecology at the University of Limerick.