We all know from science class that precipitation is when water droplets fall from the clouds, but there's also a biological version where microbial showers help water the plants.
This process called bioprecipitation starts when bacteria form colonies on the surface of plants. Winds will then sweep the bacteria into the atmosphere, and ice crystals form around them.
Water molecules clump onto the crystals, turn into rain or snow and fall to the ground. When precipitation occurs, the bacteria have the opportunity to make it back down to the ground. If even one bacterium lands on a plant, it can multiply and form colonies, thus causing the cycle to repeat itself over and over.
The discovery of bioprecipitation has many far reaching implications. For example, a reduced amount of bacteria on crops could affect the climate. Because of the bioprecipitation cycle, overgrazing in a dry year could actually decrease rainfall, which could then make the next year even dryer.
This discovery reminds us once again of the importance of microbes in our environment, even far up in the sky.