High-flying bugs cause bad weather?

London, May 25 (Agencies): High-flying bacteria in the atmosphere may be playing a leading role in causing bad weather, scientists say. Researchers from Montana State University in the US found numerous airborne microbes in the centre of hailstones, which suggests that the bugs are not only responsible for hail storms, but also for other weather events.
All precipitation -- rain, hail, snow or sleet -- begins with ice crystals forming around cloud particles, and it's believed that dust grains and pollution droplets may both serve as "nucleating particles". But the new finding, the researchers said, has helped confirm suspicions that in many cases living micro-organisms cause the rain to fall, the Daily Mail reported.
Lead researcher Dr Alexander Michaud said: "Bacteria have been found within the embryo, the first part of a hailstone to develop. The embryo is a snapshot of what was involved with the event that initiated growth of the hailstone.
"In order for precipitation to occur, a nucleating particle must be present to allow for aggregation of water molecules. "There is growing evidence that these nuclei can be bacteria or other biological particles."
For their research, Dr Michaud and his team analysed hailstones over 5cm in diameter that were collected after a storm in June last year. The large stones were separated into four layers, each of which was analysed in turn.
Living bacteria that could be grown in the laboratory were present in the highest numbers in the inner cores of the hailstones, the researchers found. A bug that infects plants, Pseudomonas syringae, is the most well-studied biological rain-maker.
"Ice nucleating strains of Pseudomonas syringae possess a gene that encodes a protein in their outer membrane that binds water molecules in an ordered arrangement, providing a very efficient nucleating template that enhances ice crystal formation," said co-researcher Dr Brent Christner of Louisiana State University in the US.
Computer simulations suggested that high concentrations of biological particles may influence precipitation levels at the ground, cloud cover, and even the way the Earth is insulated from solar radiation, the researchers said. The new findings were presented at the meeting of the American Society for Microbiology in New Orleans.

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