An international research team led by Konrad Meister from Boise State University’s Department of Chemistry and Biochemistry and the Max Planck Institute for Polymer Research announced on Mar. 13 the discovery of a new class of proteins in lower fungi that help water freeze more easily.
The study is significant because it reveals how certain fungi, specifically those in the Mortierellaceae family, use a genetic blueprint originally from bacteria to produce water-soluble proteins that efficiently promote ice formation. These findings could have practical applications in freezing technology, including cryopreservation, food processing, and snow production.
The researchers found that while bacteria such as Pseudomonas syringae are known for their ice-nucleating proteins, the structure of similar proteins in fungi had not been well understood until now. The team sequenced genomes from ice-active fungi collected during polar expeditions and discovered genes closely related to those found in ice-active bacteria. Unlike bacterial proteins that require membrane embedding to function, the fungal versions are water-soluble and unusually stable.
Phylogenetic analysis suggested that the gene responsible for these proteins was likely transferred from bacteria to a fungal ancestor long ago. Rosemary Eufemio, a Biomolecular Sciences Ph.D. student at Boise State University involved in the research, said: “It’s a bit the same and yet different. Fungi use the same repetitive sequence architecture as bacteria for their ice-forming sites, but have made them more soluble and stable, which probably benefits their ecological function.”
To confirm their findings, scientists introduced two identified fungal genes into non-ice-active yeast and bacteria; these modified organisms then gained ice-nucleating abilities. Meister said: “Soluble ice-nucleating proteins are easier to isolate, handle and integrate into formulations and technological processes than membrane-bound ones. This opens up new possibilities for controlled freezing in the cryopreservation of cells and organs, food processing and snow production.”
Janine Fröhlich from the Max Planck Institute for Chemistry explained that this ability gives microorganisms survival advantages by allowing them to be transported over long distances through precipitation: “This allows bacteria and fungal spores to be transported over long distances and reach new habitats such as plant surfaces, soils or other geographical regions.”
The study appears in Science Advances under the title “A Previously Unrecognized Class of Fungal Ice-Nucleating Proteins with Bacterial Ancestry.”
