Cloudy with a chance of microbes
By Zeke Barlow
As children, we are taught about the beautiful simplicity of the water cycle.
Precipitation cascades from the sky, falls onto plants and ponds and people, then evaporates back into the atmosphere and eventually descends back to Earth.
But what if it isn’t that simple? What if instead of just modest H2O, there were also millions of microbes in the rain? What if these microbes then went back up into the atmosphere and became parts of clouds again? What if these bacteria and fungi and other tiny organisms actually contributed to the formation of rain itself?
Turns out, there is plenty of evidence for this.
“Clouds are actually teeming with microbial life,” said David Schmale III, an associate professor in the Department of Plant Pathology, Physiology, and Weed Science. “But little is known about microbes in the rain.”
Schmale and Boris Vinatzer, an associate professor and geneticist in the same department, are part of an international team that is leading a first-ever study to examine and run DNA analyses on millions of microbes that hit the earth with each passing raindrop.
The work is being sponsored by a $2 million grant from the National Science Foundation’s Dimensions of Biodiversity Program, which asked scientists around the world to examine biodiversity in all corners of the world. While lots of work has been done to catalog microbes that live in the sea and on land, the study of microbial life in the atmosphere and in rain is largely unexplored.
Vinatzer and Schmale, along with visiting postdoctoral research associate Caroline Monteil of the French National Institute for Agricultural Research, are collecting samples of rain in buckets at Virginia Tech’s Kentland Farm. But because rain serves as an excellent atmospheric scrubber, Schmale will also gather precipitation from clouds using unmanned aerial vehicles to collect untainted samples for testing.
The group is working with Brent Christner of Louisiana State University, Caroline Weber of Idaho State University, David Sands of Montana State University, and Cindy Morris, also of INRA.
In the coming years, samples will be collected in Louisiana, Idaho, Montana, and France in order to glean a snapshot of microbial life in rain around the world. The team will also examine microbial diversity in glacial ice core samples to see if the atmospheric microbial makeup has changed since the 1700s.
“We still know very little about the importance of rain in plant, animal, and human health, so this work has the potential to paint a picture of our environment that has never been done before,” Vinatzer said.
The team has already cultured and identified thousands of microorganisms from rain that fell in Blacksburg this year.
Many of the bacteria will be characterized in detail by sequencing their genomes and testing them for their ability to catalyze the formation of ice. This could lead to more accurate weather forecasting and could potentially help with cloud seeding — when clouds are injected with a material that encourages rain.
Mark Twain once famously groused that everyone complains about the weather, but nobody does anything about it. Too bad he never got to meet Schmale and Vinatzer.