Fog and aerosol environmental samples Metagenome
Bacteria are ubiquitously found in suspension in the atmosphere, though it is unclear if they are active or simply being transported with the wind in an inactive state. Through a two-year long study of overland radiation fogs, we show that fogs constitute a transient hub of microbial biomass in the atmosphere. Bacterial concentrations in fog droplets approached those of continental freshwaters, their microbiomes well differentiated in composition and consistently and strongly enriched in Methylobacterium-like species. There, metabolically active, growing bacteria degrade toxic volatiles like formaldehyde at unprecedently high rates. This suggests that atmospheric water should be considered an aquatic habitat, and highlights the unique role of fogs in atmospheric chemistry, and has implications for the harvesting of fogs as a source of fresh water for human use.