Purple sky in Japan | Twitter photo: @ara_to1 Microbes are the truly dominant group of lifeforms. These invisible pieces of biogenic matter have been running Earth’s affairs for billions of years. Plants and animals popped up as the by-products of microbial mergers relatively recently in our planet’s history.
Understanding microbes is not easy. It took us some time to learn about the existence of the human microbiome , the collection of viruses, bacteria and fungi inside and outside our bodies that connects us to the rest of the microbial cloud that exists everywhere life can survive.
We are now learning that there is even a microbiome high in the sky. These are microbes that are swept into and then reside in the lower parts of the atmosphere. This includes the mid and upper troposphere at altitudes of between 8km and 12km above the ground, and the lower stratosphere at altitudes of up to 15km. What’s more, by joining the planetary wind systems, these lifeforms create microbial highways in the sky that transport them across the world.
Scientists first reported the existence of sky-bound bacteria in a couple of pioneering studies published in 2013 and 2018 . These were not isolated microorganisms found by chance. Instead, bacterial communities straddle the sky in large numbers, in the region of hundreds of thousands of bacteria for each cubic metre of air in the troposphere.
Between 60% and 100% of the bacteria in collected samples were alive and they typically lived in the sky for longer than five days. Analysing their genetic material confirmed the presence of dozens of different bacterial species. However, the tropospheric bacterial communities […]