Snow is Filled with Bacteria, New Study Shows

By Anastacia Mott Austin

Ah, that first snowfall of the winter season. So clean, fresh, sparkling white, covering everything with a soft blanket of……bacteria?

That’s what scientists from Louisiana State University are saying this week, after completing a study about how snow is formed in the clouds.

The droplets of water and crystals of ice formed in clouds that release precipitation need solid molecules around which to form, say the researchers, and their study showed that the primary source for these molecules are airborne particles of bacteria.

Said microbiologist Brent C. Christner, lead author of the study published in this week’s edition of Science journal, "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."

The study is important because it allows us to examine how snow and rain form, possibly impacting future rainfall levels and even broadening our knowledge of how global warming affects weather patterns. The bacteria molecules help rain droplets or snow crystals form in higher temperature conditions than other air particles like soot or dust. In essence, they keep temperatures lower by accelerating the freezing process.

"The organisms don’t grow in elevated temperatures," said Christner to Associated Press reporters. "If the world is heating up then that means less growth and maybe less rain."

After sampling snow from a variety of locations worldwide, Christner and his team found that the bacteria molecules were present in over 85% of their samples.

The most common form of bacteria found in the samples was pseudomonas syringae, a widespread germ known to cause diseases in plants. It is thought that the bacteria infect a plant then dissipate into the atmosphere where they are redeposited on other plants in the form of rain or snow.

This type of bacteria has commonly been seen as a pest, but after the recent research, Christner wonders if it should be given a new reputation. "A bacterium only implicated as bad might actually have an important role, a role we haven’t realized," Christner said. "The question is, are they a good guy or a bad guy? And I don’t have the answer to that."

One thing is for sure, the snow-making bacteria are everywhere, and their impact should not be overlooked. "The role that biological particles play in atmospheric processes has been largely overlooked. However, we have found biological ice nuclei in precipitation samples from Antarctica to Louisiana. They’re ubiquitous," wrote Christner in the study’s report. "Our results provide an impetus for atmospheric scientists to start thinking about the role these particles play in precipitation."