Microbial richness and air chemistry in aerosols confirm 2,000-km long-distance transport of potential human pathogens

Air samples taken at altitudes up to 3,000 metres over Japan unveil the presence of a wide array of microbes, some of which are potentially pathogenic to humans, contain resistance genes and are transported thousands of kilometres away by sub-micron aerosols in strong winds far from the surface. We could trace the origin and direction of winds to a densely agricultural area in NE China, while controlling for no entrainment of surface air in the way between. The chemical matrix of bioaerosols confirmed an agricultural origin and the rich content in trace elements, some of which very toxic, confirmed the likely relationship with fertilisers and bioremediation practices of agricultural soils in remote locations in NE China.Pathogens can be airborne, but little is yet known about the diversity of microbes that can survive at very high altitudes, where the conditions are harsh. In the free troposphere winds can disperse particles very long distances, and the 10 tropospheric flights we conducted over Japan uncovered a rich microbial diversity at high altitudes. Most studies have been performed only at a few metres above the ground or the ocean. 266 fungal and 305 bacterial genera associated with the aerosols were identified, some of which with species potentially pathogenic for humans, animals or plants. A small portion could be cultured and proven viable and in a majority of cases, contained natural resistance genes, even multidrug resistant strains were identified.While the study does not prove a causal link between the presence of known human pathogens in aerosols and health effects, it does emphasise the need to further explore the spread of different microbial pathogens over long distances. Also this represent a shift in how we thought that microbial biodiversity can be seeded among ecosystems and how resistance genes can be propagated in the environment.