Hailstones Full Of Bacteria And Organic Chemicals Says Study
January 24, 2013

Hailstones Chock-Full Of Bacteria And Chemicals That May Affect Weather Patterns

Lee Rannals for redOrbit.com - Your Universe Online

According to a study published in the online journal PLOS ONE, there is a rich diversity of microbial life and chemicals in the ephemeral habitat of a storm cloud.

A Danish research team at Aarhus University analyzed hailstones recovered after a storm in May 2009 and found that they carried several species of bacteria typically found on plants as well as nearly 3,000 different compounds commonly found in soil.

The hailstones had very few soil-associated bacteria or chemicals typically found in plants, according to the researchers. Three of the bacterial species that they found were discovered in almost all of the hailstones they studied, and they could present "typical" cloud inhabitants, the study authors said.

Hailstones are a form of solid precipitation, consisting of 0.2- to 8-inch lumps made up mostly of water ice. The formation of hailstones requires environments of strong, upward motion of air with a parent thunderstorm and lowered heights of the freezing point.

"Those storm clouds are quite violent phenomena," said study co-author Tina Santl Temkiv, an environmental chemist at Aarhus University in Denmark. "They are sucking huge amounts of air from under the clouds, and that's how the bacteria probably got into the cloud."

According to the researchers, the enrichment of certain plant bacteria and soil chemicals in the hailstones reveal how specific processes during the lifetime of a cloud may impact certain types of bacteria more than others.

The team also suggests that these processes could affect the long-distance transportation and geographical distribution of microbes across the planet.

"When we started these analyses, we were hoping to arrive at a merely descriptive characterization of the bacterial community in an unexplored habitat," explained Ulrich Gosewinkel Karlson, leader of the aeromicrobiology research group at Aarhus University. "But what we found was indirect evidence for life processes in the atmosphere, such as bacterial selection and growth."

The team studied 42 hailstones that formed in a thunderstorm over Ljubljana, Slovenia in May 2009. After removing the outer layer and sterilizing the hailstone, they analyzed its chemical composition as well.

They were able to identify literally thousands of organic, carbon-containing compounds, said Temkiv. They also found several species of bacteria that normally live on the external surfaces of plants. Some of the bacteria even produced a pinkish pigment that allows them to withstand ultraviolet rays in the atmosphere.

Other bacteria found in the hailstones act as ℠seeds' for ice crystals to attach to in the clouds. When these same ice crystals grow large enough, they plummet to the ground as rain, snow or hail.

Temkiv said that their study suggests that these tiny bacteria may actually be influencing regional weather patterns.

"They may be growing in clouds, increasing in number and then modifying the chemistry in the cloud but also in the atmosphere indirectly," he explained. Quite a feat for a microscopic, single-celled organism.