The biosphere is a truly vast cosmic cloud dominated by microbes. Even though this biosphere description places us, other animals, and plants in the evolutionary back corner, it tallies with the history of life. Microbes, invisible and air-floating pieces of biogenic matter, have been running the bio-geochemical affairs on Earth for billions of years. Plants and animals popped up as the by-products of microbial mergers relatively recently.
Understanding microbes is not easy. It took us some time to learn about the existence of the human microbiome – viruses, bacteria, archaea, and fungi, inside and outside our bodies that connect us to the cosmic microbial cloud. We are now learning that there is even a microbiome high in the sky. These are bacteria and viruses residing in the mid and upper troposphere, and lower stratosphere, at 8-15 km altitude. The microbial cloud is real.
In a couple of pioneering studies, published in 2013 and 2018, scientists discovered bacteria high in the sky. These are not some isolated microorganisms found by chance. Instead, bacterial communities straddle the sky in large numbers. By joining the planetary wind systems bacteria form microbial highways in the sky. The sky may virtually be alive and teeming with microbes. A kind of bacterial Lucy in the Sky with Diamonds, from the Beatles song. But bacterial Lucy is not keen on diamonds. She seems to prefer ice.
Some bacteria promote freezing of water in the air. Bacterial-borne ice particles become ice nuclei required for the cloud formation. Other bacteria act as cloud condensation nuclei without freezing. So bacteria play an important role in the process of aerosol-cloud-precipitation that is behind the atmospheric chemistry. But forget chemistry for a moment. Understanding microbial Lucy and her highways in the sky can help us learn how disease-causing microbes are transported over planetary-scale distances.
We now know that microbial Lucy is not only made up of bacteria. She also contains viruses and even fungi. In a recent study, scientists found that viruses are falling from the sky in large numbers, like invisible snowflakes covering the Sierra Nevada Mountains where viral detectors have been placed. Thanks to microbial highways in the sky, genetically identical viruses can be found over the Sierra Nevada Mountains and Californian vineyards.
An example of a disease agent carried over the microbial highway is the agent causing Kawasaki disease. The disease affects children leading to heart problems. It is not known whether the cause of Kawasaki disease is an infecting or genetic agent. However, a group of Japanese scientists has shown that the causing agent may be a fungal toxin. The toxin is carried over long distances from China to Japan by the microbial highway in the sky. The analysis of air samples over Japan during the season of Kawasaki disease confirmed that the most dominant microbial species is the fungus Candida. As viruses spill over the microbial highways and fall on Sierra Nevada Mountains, so do fungal spores of Candida over sampling sites in Japan.
The whole world is watching the saga of the current COVID-19 pandemic. We have been told that the virus spreads through human contact. However, a group of doctors has recently warned WHO that the viral particle may be travelling through the air. This is consistent with the concept of microbial highways and the raining of viruses from the sky.
In the most recent development, a group of international scientists led by Professor Chandra Wickramasinghe investigated the global spread of the COVID-19 virus. The pattern of the early stages of pandemics, affecting countries mainly in the 30-50oN latitude zone is explained by dust carrying the virus by a circum-global jet-stream. In other words, the virus is carried by the microbial highway in the sky.
The sub-tropical microbial highway in the high-altitude troposphere lies above northern China in the early spring-time, so it appears to be the most likely carrier. The study hypothesizes that wind-borne dust carried the COVID virus over southern USA states, thence across the Atlantic to Portugal and further states to the east. In this model the primary in-fall of the infective dust depends on the jet-stream interaction with regional weather systems, causing the incidence of COVID cases in various countries underneath the jet-stream. The exceptional case of Brazil could be due to the Azores cyclonic weather system west of Portugal diverting part of the jet-stream into the south-westerly trade winds during spring-time when these winds penetrate to Brazil.
The study implies that dust particles, including invisible microdust, protect the virus from the destructive ultraviolet radiation and so can carry the infection around the globe. Air travel appears to be a less important carrier. Urban dust also serves as a carrier within towns and cities. This could be vitally important for local policies to combat COVID-19. The filters on air conditioning systems in shops, offices, and transport vehicles should be checked or upgraded and people should wear facemasks outdoors on urban streets at all times. When the virus is abundant in the environment, contact tracing plus isolation will be ineffective in suppressing it. The use of facemasks in public spaces (replacing a 2 metre distancing rule) may be a way of unlocking the dreadful crisis faced by many industries, including theatre, music halls, restaurants, etc.
So microbial Lucy in the Sky and her highways may transport the COVID-19 virus around the globe. But the idea of microbial Lucy looming over the Earth may be incomplete. Fred Hoyle and Chandra Wickramasinghe developed the modern panspermia theory. Viruses and bacteria may be travelling over cosmic microbial highways. Our Lucy in the Sky maybe just a local girl, perhaps chatting to her cosmic friends over endless cosmic microbial highways.
