A new study that was supported by a Louisiana State University research grant informs us that snowflakes could be transporting bacteria. The majority of snowflakes, as well as rain, are formed in chilly conditions high in the sky.

The Discovery News report says that the moisture needs something to cling to in order to condense. The study conducted by Brent C. Christner, an assistant professor of biological sciences at Louisiana State University and others shows that, a surprisingly large share of those so-called nucleators turn out to be bacteria that can affect plants.

"Bacteria are by far the most active ice nuclei in nature," said Brent C. Christner

The research team sampled snow from Antarctica, France, Montana and the Yukon.

The bacteria were most common in France, followed by Montana and the Yukon, and were even present to a lesser degree in Antarctica.

Pseudomonas syringae was the most common bacteria found and it can cause disease in several types of plants including tomatoes and beans.

Pseudomonas syringae was found in 20 samples of snow from around the world and subsequent research has also found it in summer rainfall in Louisiana.

Prior to this study the reaction to Pseudomonas was to try and eliminate it; this new information calls that tactic into question.
"The question is, are they a good guy or a bad guy," Christner said, "and I don't have the answer to that."

It is now apparent that Pseudomonas is effective at getting moisture in a cloud to condense.

The question that now stands out is whether planting crops known to be infected by Pseudomonas in areas experiencing drought might help increase precipitation there by adding more nuclei to the atmosphere.

It was already understood that microbes and insects and algae blow around in the atmosphere, Christner said "but the atmosphere has not been recognized as a place where things are active. That has been changing in the last decade. In a cloud you've got water, organic carbon," everything necessary to support a microorganism.

Virginia K. Walker is a biologist at Queen's University in Kingston, Ontario, Canada, and she said that other researchers have found bacteria serving as snow nuclei, but had not identified it as Pseudomonas.

"It's one of those great bacteria ... you can find them anywhere," said Walker, who was not part of the research team. "They are really interesting."

Charles Knight is a cloud physics expert at the National Center for Atmospheric Research Boulder, Colo. Knight was not surprised by the finding, however.

At relatively warm temperatures of just a few degrees below freezing, bacteria are "remarkably effective" at attracting ice formation, said Knight, who also was not part of the research group.