Study explains how bacteria induce ice crystal formation

POTSDAM, Germany, April 25 (UPI) -- New research out of Germany highlights the ice-inducing effects of certain bacteria. The findings may have implications for variety of research fields, including climate science and horticulture.

Pure water doesn't freeze at zero degrees Celsius. In fact, pure water droplets don't freeze until the thermometer reads minus 37.

The story is different when the water is in contact with larger surfaces of ice, or when droplets aren't pure. Impurities, like bacteria, encourage the formation of ice crystals. Until now, researchers hadn't studied the molecular mechanism that induces ice formation.

Using a laser-based imaging process known as sum frequency generation spectroscopy, researchers were able to zoom in on interactions between water and protein molecules present on the surface of an ice-active bacterium called Pseudomonas syringae.

The analysis showed that the bacteria proteins generate unique ordered structures in water droplets and expel heat.

Water droplets containing Pseudomonas syringae freeze at minus 2 degrees Celsius. For comparison, water containing mineral dust doesn't freeze until it's minus 15 degrees.

An improved understanding of bacterial ice induction is important for researchers trying to curtail frost damage in agriculture, as well as scientists working to improve cloud formation and precipitation models. Ice-active bacteria can become airborne, thus triggering the formation of snow and rain clouds.

The new research also suggests scientists may be able to replicate the structure of ice-inducing bacteria proteins.

"For the future it is conceivable to produce artificial nano-structured surfaces and particles to selectively influence and control the formation of ice," Tobias Weidner, a scientist at the Max Planck Institute for Polymer Research, said in a news release.

Weidner and his colleagues detailed their latest research efforts in the journal Science Advances.

"We plan to examine the ice-nucleating proteins in isolated form," added researcher Janine Frohlich-Nowoisky of the Max Planck Institute for Chemistry. "Currently, we are still analyzing whole bacterial cells and cell fragments. Additionally, we want to extend the analyses to fungal ice nuclei."