Published on 4/25/2026
Some countries use silver iodide to pollinate clouds and make them drop rain, but scientists have long wondered: What happens naturally that helps this happen?
You might be surprised to learn that one of the main actors in this process is a fungus that grows on the ground, and perhaps our feet set foot on it without us knowing. What do these fungi do, and how do their influence reach from the ground to the sky? These and other questions were answered by a study published by the journal Science Advances.
The study explained, for the first time, the details of a natural cycle whose main role is the Mortierella and Fusarium fungi, and one of the outcomes of this cycle is rainfall.
“It has long been thought that dust or salts are the primary natural catalyst for the formation of rain inside clouds,” says Diana Linares, a postdoctoral fellow in microbial ecology at the University of Limerick in Ireland, who wrote about that study in an article published on The Conversation website.
She added: “But what the study revealed was more complex, as it found that inside these clouds, water remains in a liquid state despite temperatures that may reach minus 40 degrees Celsius, in what is known as (supercooled water). In order to transform this water into ice, which is the first step towards rain, there must be a seed at which the freezing process begins, and this seed is the Fusarium and Mortierella fungi.”
Horizontal gene transfer
According to the study, these fungi secrete proteins in the soil whose properties are stimulating ice formation at temperatures much higher than normal. These fungal proteins are characterized by being smaller in size, soluble in water, and more efficient in stimulating ice formation inside clouds, even at temperatures higher than (-5 degrees Celsius).
She adds, “When the wind carries them into the atmosphere, they act as effective seeds that accelerate the formation of ice crystals, which grow and later fall in the form of rain.”
The study showed that these fungi acquired this ability through a process known as “horizontal gene transfer,” which is a mechanism that allows microorganisms to exchange genes among themselves, giving them new abilities quickly. The researchers identified the bacteria “Pseudomonas syringae” as a source that helped transfer those genes to the fungi.
Environmental and practical dimensions
Diana says, “This discovery outlines the features of an amazing natural cycle, which begins with the growth of fungi in moist soil, releasing their proteins into the air, stimulating rain, which in turn promotes the growth of more fungi, in an integrated circle linking life and climate.”
This discovery has important environmental and applied dimensions, as it means, according to Diana, that deforestation is not only a loss of trees, but may lead to the disruption of this natural biological cycle responsible for stimulating rain. These results also open the door to using these natural proteins as an environmentally friendly alternative in “cloud seeding” techniques, instead of chemicals such as silver iodide.
