A recent study on the radiation haze phenomenon in Pennsylvania revealed that bacteria thriving in fog droplets actively multiply and consume toxic pollutants like formaldehyde, demonstrating remarkable biological activity in our atmosphere.
Foggy fields in Pennsylvania harbor beneficial bacteria that help detoxify the air. Image credit: Thi Thuong Thuong Cao.
“The atmosphere contains thousands to millions of bacterial cells per cubic meter,” states Dr. Thi Tuong Tuong Cao from Arizona State University and his research team.
“It’s still uncertain whether these microorganisms are active and growing in their environment or simply transported in an inactive form.”
“Our understanding of the types of bacteria present in ground-level fog is still quite limited.”
To explore the role of atmospheric droplets as microhabitats for these microorganisms, Cao and his team executed an experimental study involving 32 radiation fog events over two years in central Pennsylvania.
While they found that less than 1% of fog droplets harbored bacteria, their collective presence indicated a surprisingly high lifespan.
“Combining all the droplets reveals that their bacterial concentration parallels that of the ocean,” noted Ferran García Pichel, another Arizona State University professor.
“A single thimble of mist contains around 10 million bacteria.”
Among these microorganisms, Methylobacteria were particularly notable. Air samples taken before fog formation showed fewer of these bacteria than those collected after the fog appeared, suggesting that fog enhances their population.
Methylobacteria utilize simple carbon compounds, including harmful chemicals like formaldehyde, known for contributing to ozone smog and posing health risks.
“Upon microscopic examination, we observed that the bacteria were enlarging, dividing, and reproducing,” Cao explained.
“We discovered they use formaldehyde as a nutrient for growth.”
Remarkably, these bacteria eliminated significant amounts of formaldehyde swiftly, indicating that they were not merely feeding on it. At elevated levels, this chemical can be toxic to bacteria, prompting them to degrade it into carbon dioxide, a beneficial process for both microorganisms and humans.
“Awareness of biological activity in clouds has only recently gained traction, leaving much still unexplored,” commented Pierre Herkes, an Arizona State University professor.
“For instance, nighttime presents fewer atmospheric chemical reactions, primarily driven by sunlight. However, if bacteria maintain their activity at night, they hold significant ecological importance.”
“The fascinating aspect is how much remains unknown about the micro-ecosystem within fog and clouds. Do bacteria vary by fog origin? What sustenance do these other bacteria seek? And how do they influence air quality?”
“The sky truly is the limit!” exclaimed Professor García Pichel.
The study is published in this week’s edition of mBio.
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Thi Tuong Tuong Cao et al. 2026. Growth of photoheterotrophs and formaldehyde degradation by Methylobacterium in radiation fog. mBio 0:e00463-26; doi: 10.1128/mbio.00463-26
Source: www.sci.news
