Highlights

Wind-Riding Microorganisms

Samples collected during airplane flights reveal that a wide diversity of microorganisms, some of them potentially pathogenic, can thrive in the troposphere – where they can travel vast distances on wind currents

Samples collected during airplane flights reveal that a wide diversity of microorganisms, some of them potentially pathogenic, can thrive in the troposphere – where they can travel vast distances on wind currents

Our findings represent a paradigm shift in how airborne microorganisms thrive and travel

Some microorganisms travel by air. But how high and how far can they go? This was the question that Xavier Rodó and colleagues set out to answer. After conducting ten tropospheric flights between 1000 and 3000 metres above Japan and analysing 22 air samples, they made a surprising discovery: viable bacteria and fungi, associated with aerosols originating thousands of kilometres away, were present at these high altitudes.

We know that above a certain point in the troposphere, called the planetary boundary layer, certain materials can be transported over long distances because the air in that region is isolated from the surface and there is less friction. But we did not suspect that viable microorganisms could be there also,

– Xavier Rodó.

Microbes on the move

DNA sequencing identified over 260 fungal and 300 bacterial genera, some of which are known to be potentially harmful to humans, other animals or plants. Bacteria such as Escherichia coli, Clostridium difficile, and Acinetobacter baumannii were identified, as well as some fungi that can cause disease in immunocompromised individuals. Furthermore, bacteria collected from the air were found to be viable, and some were resistant to one or more commonly used antibiotics. This discovery, made in collaboration with Jordi Vila’s team, suggests that antimicrobial resistance may spread via tropospheric bridges, which connect air from distant regions of the world.

Long-distance travel

Chemical analysis of the aerosols confirmed an agricultural origin, linking them to intensively farmed croplands in northeast China more than 2,000 km away. Simulations conducted by the researchers support the possible transport of particles by air masses that generate in northeast China and descend to land in Japan.

This study reveals an unprecedented diversity of microbes hitching rides on tropospheric winds and traveling vast distances across the globe,

– Rodó.

While it 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 these pathogens over this previously unrecognised route.

References

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