We already blame bacteria for spoiling our food, damaging our gardens, causing all sorts of infections and illnesses and making us squirm and sneeze.
Now, scientists say, we may be able to add bad weather to the list of the one-celled organisms' troublesome deeds, too.
According to research presented this week at the meeting of the American Society of Microbiology in New Orleans, scientists at Montana State University in Bozeman have discovered large concentrations of bacteria at the core of hailstones — a finding that suggests that bacteria or other airborne microorganisms have a role in the stones' formation.
Co-author Alexander Michaud said germs floating in the atmosphere seem to behave as "ice nucleators" — particles that allow water molecules to collect and freeze in clouds. Ice nucleation is necessary for hail, as well as rain, snow and other forms of precipitation.
The hailstone discovery is new, but scientists have been studying this phenomenon — known as bioprecipitation — for decades, said Brent Christner, a microbiologist at Louisiana State University who was also interviewed along with Michaud during the ASM meeting.
But, Christner added, there's still plenty to discover about the process of bioprecipitation. Researchers don't even really know which bugs are involved. "Ninety-nine percent of the ice-nucleating organisms haven't been described yet," he said. "It may not be exclusive to bacteria."
Scientists have discovered many proteins that help plants fight freezing, he said — adding that he expects the same is probably true of proteins that speed the process.
"We know that biology affects climate in some way. But (that it does so) directly, in such a way as this is not just fascinating but very important."