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A Louisiana State University Professor of biological sciences, Brent Christner along with colleagues in Montana and France, found evidence recently that
rain making bacteria is widely spread throughout the atmosphere.
These scientists analyzed snow samples from around the world and discovered the content of snow's "biological ice nucleators" -- tiny particles that help water vapor coalesce and freeze and that high levels of bacteria were found in most samples. (85 percent)
Christner states that, "Atmospheric scientists haven't previously recognized that these particles are so widely distributed."
The fact that bacteria could cause snow and rain was discovered previously by accident in a study co-authored by David Sands, a Montana State University plant pathologist, while he was researching Pseudomonas syringae, which caused ice to form on leaves.
P. syringae is not the only biological ice nucleator, but it is the most common, and all varieties share a protein structure that provides a scaffold for free-floating water molecules. Once bound to the bacteria and to each other, the water vapors are able to freeze, and eventually fall back to Earth.
Christner says that before now, researchers never under understood how bacteria was so widespread in the clouds.
He goes on to defend the previous researchers by saying, "It's not that these atmospheric scientists are idiots -- they're not. But biological nucleators were not previously recognized as being that abundant or important. They're going to have to revise that."
USA Today explains it better in layman's terms by saying that moisture needs something to cling to [the nucleator] in order to condense into ice and that nucleator turns out to be bacteria [Pseudomonas syringae].
Science Daily explains how this works:
Bacteria form little groups on the surface of plants. Wind then sweeps the bacteria into the atmosphere, and ice crystals form around them. Water clumps on to the crystals, making them bigger and bigger. The ice crystals turn into rain and fall to the ground. When precipitation occurs, then, the bacteria have the opportunity to make it back down to the ground. If even one bacterium lands on a plant, it can multiply and form groups, thus causing the cycle to repeat itself.
Interestingly enough, this latest study found P. syringae in 20 samples from around the world, but was also later found to be in summer rain in the state of Louisiana.
Christner and his colleagues published their results on
Feb 29 in the journal Science.
