Ancient Bacterial Gene Enables Fungi to Trigger Rain by Freezing Water

Researchers have revealed the fascinating mechanism behind certain fungi's ability to induce rain. These fungi possess ice-nucleating proteins that can freeze water at relatively high temperatures, a trait they acquired by borrowing a gene from ancient bacteria.

This discovery sheds light on the complex interactions between microorganisms and the atmosphere, suggesting fungi may play a more significant role in weather patterns and the water cycle than previously understood.

How Fungi Borrowed the Power to Freeze Water

Scientists at Virginia Tech studied fungi from the Mortierellaceae family and identified a gene nearly identical to the bacterial InaZ gene, responsible for ice nucleation. This gene was likely acquired through horizontal gene transfer millions of years ago, allowing fungi to produce proteins that initiate ice formation at temperatures around -5°C (23°F).

The Role of Ice-Nucleating Proteins in Nature

Ice-nucleating proteins enable certain bacteria and fungi to freeze water, which can damage plants or help organisms access scarce water resources. For example, fungi in lichens may use these proteins to pull moisture from humid air, creating frost that melts later to provide water.

"On mornings with high humidity and low temperatures, fungal proteins can trigger frost on lichens that then melts and provides water later in the day.",—Boris Vinatzer, Microbiologist at Virginia Tech

Fungi’s Surprising Influence on Weather

Ice-nucleating bacteria are known to be part of the water cycle, seeding clouds to form rain or snow. Fungi, which can secrete many ice-nucleating proteins, might be even more influential in this process. Their proteins can form ice crystals in clouds, potentially triggering precipitation and impacting ecosystems on a large scale.

• Fungi secrete ice-nucleating proteins into the environment.
• These proteins act as nuclei for ice crystal formation in clouds.
• Ice crystals grow and eventually fall as rain or snow.
• Fungi may outnumber bacteria in clouds, amplifying their weather influence.

Potential Applications and Future Research

The discovery opens possibilities for environmentally friendly cloud-seeding alternatives. Currently, silver iodide—a toxic chemical—is used to induce rain. Fungal ice-nucleating proteins could serve as a benign substitute if production methods are developed. However, scientists still seek to understand the evolutionary advantages fungi gain from this ice-forming ability.

"These proteins could be an alternative to toxic silver iodide. If we can figure out how to produce them, why not use them instead?"—Boris Vinatzer