Winter sports areas around the world employ some microscopic help when Mother Nature is being finicky with snow production. Pseudomonas syringae, an ice-active bacterium, boasts a high-ice nucleating ability. An inactive form of the bacterium is used in the commercial snow inducer product—Snomax.
Publishing in Science Advances, researchers from the Max Planck Institutes for Chemistry and for Polymer Research zeroed in on the molecular mechanism that gives this bacteria the ability to form ice.
“With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins,” the researchers wrote. “Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequence for cloud evolution, precipitation, and climate.”
Using a technique called sum frequency generation spectroscopy, the researchers glimpsed how the bacteria exerted influence over a nearby water network.
“The interactions of specific amino-acid sequences of the protein molecules generate water domains with increased order and stronger hydrogen bonds,” according to the Max Planck Institutes. “Additionally, the proteins remove thermal energy from the water into the bacteria. As a result, water molecules can aggregate into ice crystals more easily.”
The bacterium is capable of inducing freezing in water droplets at negative 2 C. Mineral dust, or atmospheric aerosols, trigger ice formation only when below negative 15 C.
Tobias Weidner, one of the study’s authors, told Popular Mechanics that pure-water droplets in the atmosphere sometimes won’t freeze until reaching negative 40 C.
According to The Verge, P. syringae has been found in snowfall around the world. The bacterium’s properties have led scientists to believe they’re integral to cloud formation and rainfall. It is believed the bacteria are blown from the ground to the sky. However, their role in causing precipitation has never been established, Russ Schnell, of the National Oceanic and Atmospheric Administration, told the media outlet.
The researchers said they hope to replicate the bacterial ice nucleating mechanism, and use it for other applications.
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