When you go skiing in the winter, and see those big machines spitting out snow, know that they are spitting out purified proteins made from dead bacteria. I didn’t realize this until recently! Basically, they take Pseudomonas syringae cells — not engineered; a natural microbe found on plants — and grow them up in huge bioreactors. The cells make ice-nucleating proteins, which sit on their outer membranes and help ice crystals form. The cells are concentrated, freeze-dried, and sterilized until only these proteins remain. The reason these proteins are useful is because they help water molecules form ice more quickly. Water can remain liquid even below 0°C, and only freezes when enough molecules form into a crystal. The proteins have, on their surfaces, repeating snippets of amino acids that help water molecules organize into that shape. So these snow machines just blast super cold water with these proteins, and the two hit the air, mix together, and immediately freeze into snow.