Cloud-Borne Bacteria May Affect Human Health and the Environment

Louis Pasteur opened a glass flask on Montanvert Glacier in the French Alps in 1860 and collected some air. A few days later the bottom of that flask was teeming with goo--proof to Pasteur and his colleagues that there was something in the air, something invisible but quite real. Today we understand what that invisible stuff is--microbes aloft in our atmosphere--but despite the more than 150 years that have passed since Pasteur's experiment, scientists are just beginning to understand how microorganisms in the air affect life on earth.