Fungi Can Trigger Ice Formation in Clouds and That Could Change Weather Science
- Gauri Khanna
- Apr 13
- 4 min read
Too long to read? Go for the highlights below.
Fungal proteins can trigger ice formation in clouds, offering a potentially safer alternative to silver iodide: the toxic compound currently used in cloud seeding.
The gene responsible appears to have bacterial origins, acquired by a fungal ancestor through horizontal gene transfer hundreds of thousands to millions of years ago.
Unlike bacterial equivalents, the fungal proteins are cell-free and water-soluble, making them promising for frozen food production and cryopreservation of biological materials.
A newly identified class of fungal proteins can seed ice crystals at relatively warm subzero temperatures, with potential applications in cloud seeding, frozen food production, and climate modelling.
A Fungal Role in Rain Formation
Cloud seeding is the practice of releasing particles into clouds to trigger rainfall. It has been used since the 1940s to encourage precipitation in drought-prone regions, clear fog from airports, and attempt to suppress hail. The standard material is silver iodide, whose crystalline structure mimics that of ice and causes water droplets to freeze around it. The problem is that silver iodide is toxic, which creates regulatory and environmental complications wherever it is used at scale.
New research published in Science Advances (Eufemio et al., 2026) by an international team including scientists at Virginia Tech has identified a class of fungal proteins capable of nucleating ice, triggering the formation of ice crystals, at relatively warm subzero temperatures. The finding revives a long-standing but under-explored question: could biological molecules do what synthetic particles currently do, more safely and at lower cost?
Ice Nucleation: What It Is and Why Temperature Matters
Ice nucleation is the process by which water molecules begin to organise into a crystal lattice: the starting point for a snowflake or raindrop. Pure water, in the absence of any nucleating particle, can remain liquid well below 0°C. Nucleating agents, whether mineral, bacterial, or, as this research shows, fungal, provide a surface or molecular template that allows ice to form at much warmer subzero temperatures. The higher the temperature at which nucleation occurs, the more practically useful the agent.
Scientists have known since the early 1990s that some fungi can trigger ice formation, but the specific molecular mechanism remained unclear. Only recent advances in genome sequencing and computational analysis allowed the researchers to examine fungi in the Mortierellaceae family and pinpoint the responsible gene.
A Gene With Unexpected Bacterial Origins
The gene's origin adds an evolutionary dimension to the story. The team found strong evidence that it was acquired from bacteria through horizontal gene transfer which is a process by which genetic material moves between unrelated organisms, common in bacteria but relatively rare in fungi. The transfer appears to have happened at least hundreds of thousands of years ago, possibly millions, and the gene has since been refined over time, becoming more effective at triggering ice formation.
What precisely the fungi gain from the ability to nucleate ice remains unclear. One hypothesis is that it assists in breaking down organic matter by physically disrupting plant cell walls through frost damage. Another is that it plays a role in dispersal, since ice formation in clouds could carry fungal particles to new environments. The researchers do not yet have a settled answer.
Practical Applications: Food, Medicine, and Climate
The most immediate practical distinction between fungal and bacterial ice-nucleating agents is physical. Bacterial versions are membrane-bound: meaning to use them, you need the whole bacterial cell. Fungal proteins, by contrast, are cell-free and water-soluble, which means they can be isolated as a single well-defined molecule and applied without any accompanying cellular material. That distinction matters considerably in regulated contexts.
In frozen food production, this could allow manufacturers to freeze products at higher temperatures, reducing energy use and improving texture, using a chemically defined additive rather than whole bacterial cells. In cryopreservation of biological materials such as sperm, eggs, embryos, and tissues, the ability to trigger ice formation early, before temperatures fall to the point where cellular damage accelerates, could improve preservation outcomes. Current cryopreservation protocols rely on chemical agents that can themselves be toxic to cells; a naturally derived protein that works at milder temperatures offers a cleaner alternative.
For cloud seeding specifically, the researchers suggest that if fungal proteins can be produced in sufficient quantity at low cost, they could replace silver iodide in weather modification programmes; removing the toxicity concern without sacrificing efficacy.
Implications for Climate Modelling
Beyond direct applications, the research carries implications for how accurately scientists can model cloud behaviour. Ice formation in clouds affects how much solar radiation is reflected back into space versus transmitted to the Earth's surface: a variable with direct consequences for temperature and precipitation modelling. If fungal ice-nucleating proteins are present in clouds in meaningful quantities, they may already be influencing weather patterns in ways that current models do not account for.
The team notes that knowing the specific molecular structure of the protein will make it considerably easier to survey how much of it exists in the atmosphere. Over time, that data could feed into more accurate climate models: a modest but concrete contribution to one of the more intractable problems in environmental science.
