While fog can create an eerie, lonely atmosphere, it’s teeming with life. Scientists have found vibrant microbial communities in low-hanging clouds, including bacteria that can detoxify air pollution. And these microbes could play a larger role in our air quality than previously expected.
Misty microbes
Fog water can have “bacterial concentrations similar to those in continental or marine bodies of water” and “contain microbiomes well-differentiated in composition from those in the dry aerosol microbiomes,” said a study published in the journal mBio. While scientists have known that bacteria and other microbes exist in the air, not much was known about “whether those airborne microbes are doing much,” be it “growing, feeding, dividing and changing the air around them” or “simply waiting to land somewhere better,” said ZME Science.
Fog is “basically just a cloud that’s low to the ground — water vapor that has condensed or frozen to form tiny droplets or crystals in the air,” said The Weather Channel. Researchers focused on radiation fog, which is the still kind that “occurs on clear nights as the ground cools the moist air immediately above it.”
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They “collected and analyzed samples from 32 separate fog events along with aerosol particles gathered before, during and after fog formation,” said a release about the study by Susquehanna University. The findings showed that fog is “more than a vehicle for transporting microbes” and could be a “habitat where bacteria can thrive and positively influence atmospheric chemistry, air quality and even climate processes.”
While “fewer than 1% of fog droplets contain bacteria,” when “averaged together, they represent an astounding amount of life,” said a release by Arizona State University (ASU). “When you take all of the droplets together, the concentration of bacteria is the same as in the ocean,” said study co-author Ferran Garcia-Pichel, the director of the ASU Biodesign Center for Fundamental and Applied Microbiomics, in the release. Each fog event had an average of 188 unique bacterial signatures, and the “communities of microbes present were similar across all fog samples” but “differed quite a bit from those found in air without fog,” said Science News Explores.
Cloud cleaning
Scientists identified Methylobacterium as “one of the most abundant bacteria in the samples,” said the Susquehanna release. These microbes “consume single-carbon compounds such as formaldehyde,” which is a common air pollutant “resulting from the combustion of carbon fuels that contributes to ozone smog and poses health risks.”
The Methylobacteria “cleared such large amounts of formaldehyde so quickly that the researchers suspected they weren’t just eating it,” said the ASU release. At “high levels, the chemical is toxic to the bacteria, so they break it down into carbon dioxide to keep the levels low,” which is a “win-win for microbes and humans alike.”
“We observed them under the microscope to see that, yes, the bacteria are getting bigger and they are dividing, so there’s growth,” making fog a microbial habitat, said lead study author Thi Thuong Thuong Cao, a postdoctoral researcher at ASU, in the ASU release. The potential for “harvesting fog for drinking water has also been up for discussion,” said The Weather Channel. “Now, we need to consider and further study if these air-cleaning benefits are too good to pass up.”
People “think of fog as just water droplets,” said study co-author Derek Straub, an associate professor at Susquehanna University, in the Susquehanna release. But there’s a “tremendous amount happening inside those droplets that we are only beginning to understand.”
