Recent evidence suggests that bacteria in clouds may have evolved the ability to make it rain as a way of dispersing themselves around the globe.
The theory-called bioprecipitation-was pioneered by David Sands, a plant pathologist at Montana State University, in the 1980s. But little information existed on how the rainmaking bacteria moved through the atmosphere until Christner and his colleagues began their work in 2005. Sands told National Geographic News that the critters may even employ creative means of transportation: For instance, they could "ride piggyback" on pollen or insects. "We thought [the bacteria] were just plant pathogens [germs], but we found them in mountain lakes, in waterfalls, in Antarctica-they get around," Sands said.
