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Everything and anything => weathEU and XEarth => : electrobleme October 02, 2009, 02:39:54

: bioprecipitation - bacteria (ice nucleators) live & move in rain clouds? Gaia?
: electrobleme October 02, 2009, 02:39:54
Gaia - bioprecipitation - ice nucleators

Rainmaking bacteria that live in clouds may have evolved the ability to spur showers as a way to disperse themselves worldwide, a recent study found.

The research gives scientists a first glimpse into the link between biology and climate, and into how the tiny organisms globe-trot with the weather cycle.

The microbes—called ice nucleators—are found in rain, snow, and hail throughout the world, according to previous work by Brent Christner, a microbiologist at Louisiana State University.

Christner had shown that, at a high enough concentration, these organisms may be efficient drivers for forming ice in clouds, the first step in forming snow and most rain.

But he hadn't been able to pinpoint their source—until now.

In the recent study, Christner and colleagues found that the critters hail from snow, soils, and young plant seedlings in such such far-flung sources as Antarctica, Canada's Yukon Territory, and the French Alps.

The bacteria may be part of a constant feedback between these ecosystems and clouds.

"This is sending ripples through the atmospheric science community," Christner said.

"This idea would have been viewed as crazy 25 years ago, but these new findings have invigorated research … in the role that biology may play in atmospheric processes."


On the ground, researchers found ice nucleators alongside aerosols—tiny particles suspended in air—that could be chemically traced back to clouds.

In some places, the nucleators had come mostly from soil and plant ecosystems, the results showed.

One possible explanation is that the bacteria rely on the atmosphere—and rainfall—to disperse, much like plants rely on windblown pollen grains to colonize new habitats, Christner said.

For instance, an organism specialized to live on plants may become airborne, spur ice formation in clouds, and then travel back to Earth with that precipitation.

This may be an important and yet unrecognized component of a bacteria's normal life cycle, according to Christner, whose results were published in November 2008 in the journal Proceedings of the National Academy of Science.

Piggyback Rides

The theory—called bioprecipitation—was pioneered by David Sands, a plant pathologist at Montana State University, in the 1980s. But little information existed on how the rainmaking bacteria moved through the atmosphere until Christner and his colleagues began their work in 2005.

Sands told National Geographic News that the critters may even employ creative means of transportation: For instance, they could "ride piggyback" on pollen or insects.

"We thought [the bacteria] were just plant pathogens [germs], but we found them in mountain lakes, in waterfalls, in Antarctica—they get around," Sands said.

Scientists still haven't identified most of the important ice nucleators in the atmosphere. For instance, a whole host of other microbes—as well as pollen grains, fungi, and other organisms—may be producing the ice nucleators detected, study author Christner added.

The vast majority of ice nucleators that are active at temperatures higher than 10 degrees Celsius (50 degrees Fahrenheit) have been found to be biological or bacterial.

Roy Rasmussen, a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, studies Earth's wintertime water cycle.

The theory that bacteria can shape the water cycle is "an interesting hypothesis, but one that is not verified, Rasmussen said in an email.

"The real issue is whether the concentration of these cells is high enough to impact precipitation formation in any significant way."

No Rain Dancing

Scientists had already suspected that cloud bacteria may be linked to plants and soils in a "feedback loop," a system of exchange between ecosystems.

In fact, these bacteria may have evolved with plants over millennia, building a dependent relationship, Sands said.

The concept also ties into Sands's ongoing study of the idea that drought cycles are connected to bacteria in clouds.

(Related: "Sun's Cycles Can Forecast Floods, Drought?" [December 10, 2008].)

For instance, if people overgraze lands, "these bacteria are without a home … and can have serious consequences, possibly, for lack of rainfall," Sands said.

Simply put, a lack of vegetation may lead to a lack of bacteria, which could limit clouds' ability to shed rain.

But drought-affected farmers have alternatives, Sands said: They may be able to choose plant species that harbor more bacteria.

"It's better than rain dancing," he added.

Sands and colleagues have a network of researchers already observing bacteria in croplands in Syria, Uzbekistan, and New Zealand.

However, he said, "We're only halfway there. We haven't proven all these things yet."
Rainmaking Bacteria Ride Clouds to "Colonize" Earth? - nationalgeographic .com (http://news.nationalgeographic.com/news/2009/01/090112-clouds-bacteria.html)
: Microbiological meteorology: biological ice nucleation and precipitation
: electrobleme October 02, 2009, 02:43:14

Microbiological meteorology: biological ice nucleation and precipitation

Microbiological meteorology: biological ice nucleation and precipitation. Certain plant-associated bacteria have the capacity to freeze supercooled water at temperatures as warm as –1° C, which is catalyzed by a protein in the outer membrane of the bacterial cell. Ice nucleating active bacteria are present at altitudes of several kilometers and have been documented in rain and snowfall. Based on the warm temperature and efficiency at which they function as ice nuclei, we hypothesize that these biotic particles have important impacts on atmospheric processes by serving as freezing catalysts in clouds, thus inducing precipitation. Glacier ice cores provide long-term records to examine linkages between airborne biological ice nucleating particles, environmental conditions, and precipitation.
Brent C. Christner - The Ohio State University (http://www.biology.lsu.edu/faculty_listings/fac_pages/bchristner.html)
: LSU Scientist Finds Evidence of “Rain-Making” Bacteria
: electrobleme October 02, 2009, 02:47:01
LSU Scientist Finds Evidence of “Rain-Making” Bacteria

LSU Scientist Finds Evidence of “Rain-Making” Bacteria
Could have implications for climate and understanding dissemination of agricultural pathogens

Brent Christner, LSU professor of biological sciences, in partnership with colleagues in Montana and France, recently found evidence that rain-making bacteria are widely distributed in the atmosphere. These biological particles could factor heavily into the precipitation cycle, affecting climate, agricultural productivity and even global warming. Christner and his colleagues will publish their results in the prestigious journal “Science” on Feb. 29.

Christner’s team examined precipitation from global locations and demonstrated that the most active ice nuclei – a substrate that enhances the formation of ice – are biological in origin. This is important because the formation of ice in clouds is required for snow and most rainfall. Dust and soot particles can serve as ice nuclei, but biological ice nuclei are capable of catalyzing freezing at much warmer temperatures. If present in clouds, biological ice nuclei may affect the processes that trigger precipitation.

The concept of rain-making bacteria isn’t far-fetched. Cloud seeding with silver iodide or dry ice has been done for more than 60 years. Many ski resorts use a commercially available freeze-dried preparation of ice-nucleating bacteria to make snow when the temperature is just a few degrees below freezing.

“My colleague David Sands from Montana State University proposed the concept of ‘bioprecipitation’ over 25 years ago and few scientists took it seriously, but evidence is beginning to accumulate that supports this idea,” said Christner.

But, what makes this research more complicated is that most known ice-nucleating bacteria are plant pathogens. These pathogens, which are basically germs, can cause freezing injury in plants, resulting in devastating economic effects on agricultural crop yields.

“As is often the case with bacterial pathogens, other phases of their life cycle are frequently ignored because of the focused interest in their role in plant or animal health,” said Christner. “Transport through the atmosphere is a very efficient dissemination strategy, so the ability of a pathogen to affect its precipitation from the atmosphere would be advantageous in finding new hosts.”

It is possible that the atmosphere represents one facet of the infection cycle, whereby the bacteria infects a plant, multiplies, is aerosolized into the atmosphere and then delivered to a new plant through atmospheric precipitation.

“The role that biological particles play in atmospheric processes has been largely overlooked. However, we have found biological ice nuclei in precipitation samples from Antarctica to Louisiana – they’re ubiquitous. Our results provide an impetus for atmospheric scientists to start thinking about the role these particles play in precipitation,” said Christner. “This work is truly multi-disciplinary, bridging the disciplines of ecology, microbiology, plant pathology and climatology. It represents a completely new avenue of research and clearly demonstrates that we are just beginning to understand the intricate interplay between the planet’s climate and biosphere.”

LSU Scientist Finds Evidence of “Rain-Making” Bacteria - lsu .com (http://www.lsu.com/UNV002.nsf/%28NoteID%29/D807D7193CA91738862573FE004E8FF8?OpenDocument)

: MSU professor's research on bacteria's role in precipitation cycle
: electrobleme October 02, 2009, 02:53:25

MSU professor's research on bacteria's role in precipitation cycle published by "Science"

A Montana State University professor and his colleagues have found evidence suggesting that airborne bacteria are globally distributed in the atmosphere and may play a large role in the cycle of precipitation.

The research of David Sands, MSU professor of plant sciences and plant pathology, along with his colleagues Christine Foreman, an MSU professor of land resources and environmental sciences, Brent Christner from Louisiana State University and Cindy Morris, will be published today in the journal "Science."

These research findings could potentially supply knowledge that could help reduce drought from Montana to Africa, Sands said.

Sands, Foreman, Morris, and Christner -- who did post-doctorate work at MSU -- examined precipitation from locations as close as Montana and as far away as Russia to show that the most active ice nuclei are actually biological in origin. Nuclei are the seeds around which ice is formed. Snow and most rain begins with the formation of ice in clouds. Dust and soot can also serve as ice nuclei. But biological ice nuclei are different from dust and soot nuclei because only these biological nuclei can cause freezing at warmer temperatures.

Biological precipitation, or the "bio-precipitation" cycle, as Sands calls it, basically is this: 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.

"We think if (the bacteria) couldn't cause ice to form, they couldn't get back down to the ground," Sands said. "As long as it rains, the bacteria grow."

The team's work is far-reaching. Sands and his colleagues have found the bacteria all over the world, including Montana, California, the eastern U.S., Australia, South Africa, Morocco, France and Russia.

The team's research also shows that most known ice-nucleating bacteria are associated with plants and some are capable of causing disease.

"Bacteria have probably been around for a million years," Sands said. "They live on the surface of plants, and may occasionally cause plant disease. But their role in rain-making may be more important."

Indeed, the implications of a relationship between rain and bacteria could be enormous, though they are yet to be proven, Sands said.

For example, a reduced amount of bacteria on crops could affect the climate. Because of the bio-precipitation cycle, overgrazing in a dry year could actually decrease rainfall, which could then make the next year even dryer.

"Drought could be less of a problem once we understand all of this," Sands said.

Sands, who earned a doctorate in pathology and bacteriology from the University of California-Berkeley, proposed the concept of bio-precipitation approximately 25 years ago, but few people believed him.

Since that time, he said, better tools have changed the research climate, because new DNA technology allows researchers to distinguish the bacteria, and giant computers allow people to do meteorological studies with satellites.

"It's fun to see something come out after 25 years," Sands said, "particularly when we knew back then it was true."

More studies must be done, though, because questions remain. For example, since the bacteria do not grow above 84 degrees, precipitation could be affected if the world's weather creeps up and reaches a cut-off point, Sands said. The researchers are also examining the bacteria to find out if they vary by region.

A diverse group of people should be interested in the research, because bio-precipitation could affect many things.

"I want people to be fascinated by the interconnection of things going on in the environment," Sands said. "It's all interconnected."
MSU professor's research on bacteria's role in precipitation cycle  - montana .edu  (http://www.montana.edu/cpa/news/nwview.php?article=5659)