Clouds may be dining cars for some germs

Imagine snacking on sweets while wrapped in a cozy bubble. Now picture this happening while floating in a cloud. It sounds like a pleasant dream. But for some lucky bacteria, it also may be a reality.

Researchers have discovered that at least one cloud-dwelling microbe — a bacterium belonging to the Bacillus genus— may dine on sugars while riding the winds in clouds. And this is not just any microbe. It’s one of the types most frequently found in the air and cloud-water droplets, reports a team of European scientists.

Mária Matulová works at the Slovak Academy of Sciences in Bratislava, Slovakia. Her team kidnapped some of the high-flying microbes. They had been riding clouds above the Auvergne region of France. These germs are known to eat and actively digest materials in the environment. But what they eat had been a mystery.

Back in the lab, Matulová’s group provided the germs a feast of sugars and starches. This meal consisted of materials commonly kicked into the atmosphere by Earthlings (yes, the human variety).

The bacteria broke down the heavenly sweets. Then they used this molecular rubble to fashion protective outer coatings for their cells. Those new shells may shield the microbes from both frigid temperatures and the sun’s potentially deadly ultraviolet radiation. Meanwhile, the high-altitude germs also may spur water-droplet formation, which could boost a cloud’s density. That, in turn, might boost precipitation downwind, the authors speculate. The researchers shared their new findings November 12 in Environmental Science & Technology.

Scientists had known for decades that clouds can host diverse communities of microbes. But researchers had suspected those germs, lofted into the air by winds, were just aimlessly hitchhiking rides, sometimes between continents. The new research shows that the germs are not just jetting long distances. Some may treat their cloud ferries like club cars, dining happily as they travel.

Power Words

bacterium(plural bacteria)  A single-celled organism. These dwell nearly everywhere on Earth, from the bottom of the sea to inside animals.

germ  Any one-celled microorganism, such as a bacterium, fungal species or virus particle. Some germs cause disease. Others can promote the health of higher-order organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

ultraviolet  A portion of the light spectrum that is close to violet but invisible to the human eye.