This could lead to advances in cryobiology
Ice-minus bacteria are notorious plant pathogens, causing up to billions of dollars of frost damage to crops annually. These same bacteria help our ski resorts stay open during warm weather by generating artificial snow. They also form precipitation in the atmosphere.
A team of scientists led by Tobias Weidner, a physicist at the Max Planck Institute for Polymer Research in Germany, has finally gotten to the bottom of what makes this species of bacteria so good at producing ice crystals. Their findings were recently published in the journal Science Advances.
It turns out that ice-minus bacteria have an important trick up their sleeve — they cause water to freeze at warmer temperatures that it normally would. Weidner told Popular Mechanics, “For example, if you have pure water suspended in the atmosphere, sometimes the water droplets won't freeze until they're at -40 degrees centigrade. But if these bacteria are around, that freezing point can drop to just -5 degrees."
The team looked at some of these ice-minus bacteria more closely using an imaging tool called a sum frequency generation spectrometer, which gently vibrates the molecules on the surface of the bacteria while it is turning water into ice. These vibrations allow researchers to see exactly what the surface molecules are doing to make ice crystals to grow.
Imaging revealed that the bacteria’s surface proteins shift water molecules ever so slightly so that they form into a neat lattice — the exact structure required for ice crystal formation.
Next, the bacteria remove heat from the surrounding area, forcing the water molecules to coalesce into ice. The scientists still don’t fully understand how the bacteria manage to eliminate heat, but this is a key feature of their unique ability to form ice.
During this heat-removing process, antifreeze proteins in the cell membrane protect the bacteria from being damaged by the cold.
"If we can figure out ways to mimic this bacteria and learn either how to initiate surface icing, or do the exact opposite and avoid it, well that could have a lot of applications,” said Weidner. These might include anything from “advances in cryobiology and learning how to keep tissues cool, to developing electric land lines that could better weather snowstorms and lots of ice."
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