Storm Clouds Crawling With Bacteria

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Hailstones: A Window into the Microbial and Chemical Inventory of a Storm Cloud


The storm clouds in Earth's atmosphere are filled with microbial life, according to a new study.

The research, published today (Jan. 23) in the journal PLoS One, revealed that hailstones  drawn from storm clouds harbor several species of bacteria that tend to reside on plants, as well as thousands of organic compounds normally found in soil. Some of the bacterial species can seed the tiny ice crystals that lead to rain, suggesting they play a role in causing rain.


"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."


   Abstract

Storm clouds frequently form in the summer period in temperate climate zones. Studies on these inaccessible and short-lived atmospheric habitats have been scarce. We report here on the first comprehensive biogeochemical investigation of a storm cloud using hailstones as a natural stochastic sampling tool. A detailed molecular analysis of the dissolved organic matter in individual hailstones via ultra-high resolution mass spectrometry revealed the molecular formulae of almost 3000 different compounds. Only a small fraction of these compounds were rapidly biodegradable carbohydrates and lipids, suitable for microbial consumption during the lifetime of cloud droplets. However, as the cloud environment was characterized by a low bacterial density (Me = 1973 cells/ml) as well as high concentrations of both dissolved organic carbon (Me = 179 µM) and total dissolved nitrogen (Me = 30 µM), already trace amounts of easily degradable organic compounds suffice to support bacterial growth. The molecular fingerprints revealed a mainly soil origin of dissolved organic matter and a minor contribution of plant-surface compounds. In contrast, both the total and the cultivable bacterial community were skewed by bacterial groups (γ-Proteobacteria, Sphingobacteriales and Methylobacterium) that indicated the dominance of plant-surface bacteria. The enrichment of plant-associated bacterial groups points at a selection process of microbial genera in the course of cloud formation, which could affect the long-distance transport and spatial distribution of bacteria on Earth. Based on our results we hypothesize that plant-associated bacteria were more likely than soil bacteria (i) to survive the airborne state due to adaptations to life in the phyllosphere, which in many respects matches the demands encountered in the atmosphere and (ii) to grow on the suitable fraction of dissolved organic matter in clouds due to their ecological strategy. We conclude that storm clouds are among the most extreme habitats on Earth, where microbial life exists.


{ Copyright: © 2013 Å antl-Temkiv et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. }


   Living on a cloud

In the past, researchers have found bacterial life in clouds that drift over mountaintops. Bacteria have been found as far up as 24.8 miles (40 kilometers) and may even survive as spores into space, Temkiv said. [Holey Clouds: Gallery of Formations Cut By Airplanes]. 


Bacteria Pseudomonas syringae, serves as the nucleus for the formation of crystal snowflakes and hail. Owner photo: Shawn Doyle and Brent Christner, Louisiana State University

Temkiv and her colleagues wanted to see if bacteria lived in the violent storm clouds that hover above the Earth's surface. To find out, they studied 42 hailstones that had formed in a thunderstorm over Ljubljana, Slovenia, in May 2009.

After carefully removing the outer layer and sterilizing the hailstone, they analyzed its chemical composition.

The team found thousands of organic, or carbon-containing, compounds — nearly as many as found in a typical river, Temkiv said. In addition, they found several species of bacteria that normally live on plants. Some of the bacteria make a pinkish pigment that allows them to withstand the punishing ultraviolet rays in the atmosphere.

Some of bacteria found are ice-nucleators, meaning they can act as seeds for ice crystals to attach to in the clouds above Earth. When these same ice crystals get large enough, they fall as rain or snow, depending on the air temperature.

The findings suggest that bacteria could influence weather patterns, possibly making rain, Temkiv said.

"They may be growing in clouds, increasing in number and then modifying the chemistry in the cloud but also in the atmosphere indirectly," she told LiveScience.

The researchers think the bacteria come from the air hovering just above Earth that gets swept into the storm clouds through updrafts. That would suggest the atmosphere is a thread that can connect distant ecosystems, and that certain bacteria may be better at colonizing faraway environments, Pierre Amato, a researcher at France's Blaise Pascal University who was not involved in the study, wrote in an email. 


09.03.2012. Hawaii was recorded hailstones with bacterial nucleus, 10.8 length and a width of 5 inches. Source: NOAA and Live Sceince

"Clouds can be thought of as transient ecosystems selecting for certain [types of bacteria] that are better fitted than others, and that can thus quickly disperse over the globe," Amato said. "Understanding how microbes disperse is relevant, of course, for epidemiology, and also for microbial ecology."











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