Pandey, R., Usui, K., Livingstone, R. A., Fischer, S. A., Pfaendtner, J., Backus, E. H., Knopf, D.A. … & Scheel, J. F. (2016). Ice-nucleating bacteria control the order and dynamics of interfacial water. Science Advances, 2(4), e1501630.
If you’ve ever skied on a mountain covered in artificial snow, you have a microbe to thank. To make fresh powder, humans have co-opted a specialized protein from a bacterium that jump-starts the freezing process when water is close to 0°C—a talent the microbes normally use to damage their host plants. But the way they do it is still mostly a mystery. To understand how the bacteria deploy their X-Men–style superpowers, researchers used a special laser-based technique called sum frequency generation spectroscopy. This allowed them to see—at a molecular level—how the Pseudomonas syringae bacteria push water around to create ice. They found, as expected, that one part of an InaZ protein on the bacteria’s surface arranges water molecules into an orderly formation—getting them prepped to form ice. But the key, according to the study in Science Advances, is the way the protein arranges water intoalternating stripes of tightly and loosely-packed molecules. The lines between these stripes may act like the boundary between water and air—which is where ice crystals are most likely to form. The protein also funnels heat away from water as it freezes, helping the process along. The discovery could help more than just makers of artificial snow. It may improve the accuracy of predictions about climate change—because the microbes also help create rain and snow high in the atmosphere.
(Video credit: Science)