Airborne Bacteria – The Nucleus of Snowflakes: Study

Teemed up with tiny bacteria that grab up water vapor in the atmosphere to make cloud droplets, the sky is not an airy, sterile realm, a new study shows.
Airborne bacteria play a more powerful role in producing rain and snow than earlier thought, researchers unfold.

Scientifically, the water droplets in clouds, along with particles of dust, soot and airplane exhaust and bacteria, which come down either in form of rain or snow, need a nucleus to cling onto in order to form in temperatures above minus 40 degrees Celsius – the process atmospheric scientists call cloud condensation nuclei (CCN).

Amazingly, snow samples picked up from three sites in Antarctica, France, and the Yukon and checked by microbiologist Brent Christner at Louisiana State University revealed that as much as 85 percent of the nuclei were bacteria.

"Nucleation events and this ice formation is widely recognized as a process that is important to the initiation of precipitation, whether it be snowfall or rain," Christner emphasizes.

Psedomonas syringae, the most common bacteria found is responsible for causing disease in several types of plants like tomatoes, green beams and other similar plants. On overall examination, the bacterium was found in 20 samples of snow from around the world and some traits in summer rainfall in Louisiana.

"Bacteria and other particles of biological origin are actually pretty good at collecting water vapor to form cloud droplets", Christner said.

"Biological particles such as bacteria are the most active ice nuclei in nature. In other words, they have the ability to catalyze ice formation at temperatures warmer than a particle of abiotic origin", he explained.

The study, supported by a Louisiana State University research grant and by the National Science Foundation and the Earth Institute at Columbia University, is published in today’s edition of the journal Science.