Chapter 24: Upper Atmosphere Microorganisms
The discovery of microorganisms - including viruses – in the higher atmosphere was unexpected to mainstream science because microorganisms cannot normally be transported from the lower atmosphere to the upper one because of the tropopause barrier:
The tropopause acts a barrier to the free movement of particles above 17km thereby making such transfer from Earth to the stratosphere very difficult.
[1]
The troposphere, the tropopause and the stratosphere
One of the few documented event able to pierce up the tropopause and possibly carry surface micro-organisms to the stratosphere is very large volcanic eruptions
[2].
But the large volcanic eruption hypothesis was dismissed when two of the papers reporting the presence of microorganisms in the stratosphere were conducted two years or more after the last major volcanic eruptions
[3]. Knowing that in two years or less, all the volcanic dust drops to the lower atmosphere
[4].
© Guiseppe Famiani
The 2015 Etna eruption. The most violent in 20 years.
The plume reaching the tropopause was blocked hence the characteristic anvil shape
So, not only microorganisms, including viruses, are present in cometary material as shown in the previous chapter,
they are also pervasive in Earth’s the upper atmosphere. The first discoveries date back to the 1930’s, almost one century ago:
[In 1936] a manned US high-altitude balloon, Explorer II, became the first air sampling mission to reach the stratosphere (up to 21 km ASL), and several viable microbes were isolated within the genera
Bacillus,
Macrosporium,
Aspergillus,
Penicillium and
Rhizopus [5]
Notice that this experiment already used autoclaved collection tubes discarding
de facto the possibility terrestrial contamination.
In the 1960’s, the air balloons flew even higher - 30 km and above – and they kept returning positive identification of microorganisms:
Although microbiological techniques available at the time were rather primitive compared to the present, there were already some intriguing
indications of the presence of extraterrestrial microbes in air samples collected at heights of 30 km and above (Bruch, 1967).
Positive detection of microorganisms at 39 km and a population density that increased with height pointed to a possible extraterrestrial[6]
In the 1970’s, the discovery of microorganisms was confirmed once again by the analysis of dust collected during stratospheric flights made by the U2 spy planes:
In the 1970s, high altitude flights (U2 aircraft) were used to collect them from the lower stratosphere, 18-20km altitude, on oiled sheets exposed outside aircraft flying at ~200m/s. This method suffered from the problem of contamination as well as breakage of the particles and a bias against small light ones (which tend to divert with the air stream). Moreover genuine interplanetary particles have to be diligently separated from terrestrial contaminants.
These so-called Brownlee particles, which were mostly in the form of fluffy aggregates of siliceous dust, have been found to
contain extraterrestrial organic molecules, with a complexity and diversity approaching that recently reported for the Murchison meteorite. In a few instances microbial morphologies were discovered within individual Brownlee particles.
[7]
© Whickramasanghe
Micron-sized carbonaceous structure in a Brownlee particle compared with a microbial fossil
It is in the 1970’s also that the highest elevation was reached when Imshenetsky and his research team collected air sample up to 85 km
[8] elevation – higher than the upper boundary of the stratosphere - from which they isolated bacteria and fungus:
In the 1970s, A. A. Imshenetsky and colleagues collected samples of air from even higher elevations, from the stratosphere to the mesosphere (48-85 km ASL), using γ-radiation sterilized meteorological rockets and investigated the characteristics of the bacterial and fungal strains isolated.
[9]
A similar experiment was conducted in 2001 in the stratosphere above India. It identified three microorganisms: two bacterial and one fungal species:
An Indian and British team of researchers led by Chandra Wickramasinghe reported on 2001 that air samples over Hyderabad, India, gathered from the stratosphere by the Indian Space Research Organisation (ISRO) on January 21, 2001,
contained clumps of living cells. Wickramasinghe calls this "
unambiguous evidence for the presence of clumps of living cells in air samples from as high as 41 km, above which no air from lower down would normally be transported".
Two bacterial and one fungal species were later independently isolated from these filters which were identified as Bacillus simplex, Staphylococcus pasteuri and Engyodontium album respectively.
[10]
In 2005, air samples were collected at altitudes of more than 40 km
[11]. The results were unexpected, not only 15 different known species of microorganisms were identified but also
three bacteria species[12] unknown on Earth until then:
In 2005 an improved experiment was conducted by ISRO. On April 20, 2005, air samples were collected from the upper atmosphere at
altitudes ranging from 20 km to more than 40 km. The samples were tested at two labs in India. The labs
found 12 bacterial and 6 different fungal species in these samples. The fungi were Penicillium decumbens, Cladosporium cladosporioides, Alternaria sp. and Tilletiopsis albescens. Out of the 12 bacterial samples,
3 were identified as new species and named Janibacter hoylei (after Fred Hoyle), Bacillus isronensis (named after ISRO) and Bacillus aryabhattai (named after the ancient Indian mathematician, Aryabhata).
These three new species showed that they were more resistant to UV radiation than similar bacteria[13]
The following year, air samples were collected, once again, above in India. Not only the stratospheric air sample led to the identification of four more unknown bacteria species but some of collected microorganisms were viable despite the added stress induced by the cryosampling and the use of a very narrow range of nutrients:
Cryosampling of the stratosphere above Hyderabad (India), resulted in
the isolation of four new species from the genus Bacillus: B. aerius sp. nov., B. aerophilus sp. nov., B. stratosphericus sp. nov., and B. altitudinis sp. nov. In many studies, such as this one, the selection of microbes cultivated was dependent on the method of collection (cryotubes were flushed with buffer that was then spread on culture media) in this case and the medium used (e.g. Luria-Bertani agar or Nutrient agar), and
effectively allowed for the recovery and cultivation only of specific microbes.[14]
The number of bacteria, archaea
[15] and fungi strains found the stratosphere and above is so impressive that DasSama
et al. compiled a non-extensive list:
© DasSama
List of microorganisms found in the stratosphere
Notice that the experiments described above collected air samples with increasingly sterile procedures:
Balloon flights launched by the Indian Space Research Organisation (ISRO) from the 1990s initially reached heights of ~30 km for sampling stratosphere CFCs, collecting frozen air in steel cylinders with all-metal valves (remotely controlled) immersed in liquid neon. The more recent flights reached heights of 40-45 km with all equipment ultra-clean and sterile to reduce contamination. In January 2001 this technique was used to collect pristine cometary dust aseptically using cryoprobes flown aboard balloons to heights of 41km
[16]
In summary, we have, on one hand, meteorites directly carrying new microorganisms, including virus as demonstrated in the previous chapter and, on the other hand, the Earth’s high atmosphere laden with microorganisms as shown in the present chapter. Could the latter be a consequence of the former? Are the Earth in-bound meteorites enabling the deposition of microorganisms in the atmosphere?
Coincidentally or not, it’s in the mesosphere - where microorganisms have been repeatedly found - where meteors begin to fragment:
A variety of microbes have been discovered in the upper atmosphere, including those who are radiation resistant, and
at heights ranging from 41 km to 77 km[17] and thus in both the stratosphere and the mesophere which is extremely dry, cold (−85 C (−121.0 F), and lacking oxygen.
It is the mesophere where meteors first begin to fragment as they speed to Earth.
[18]
One might object that microbes at such altitude would be destroyed by the ambient cold, vacuum and radiation, but it appears that some microbes are anaerobic
[19] and resistant to freezing
[20]:
© S. Grossmann
Microscope picture of psychrophilic (cold-loving) bacteria.
Some microorganisms are also resistant to radiation
[21], more than that, they thrive in such an extreme environment. Here is a striking example:
In 1960, Fowler
et al. reported a species of Pseudomonas living in a research nuclear reactor where the
average dose was estimated to be more than a million rads[22][23]
Likewise, viruses have been shown repeatedly to survive extraterrestrial conditions including cold temperature, microgravity, vacuum and intense radiations
[24].
So it seems that some microorganisms are perfectly able to survive space conditions. The debate about viability of stratospheric microorganisms was seemingly put to an end when metabolically active microbes were launched into the stratosphere and returned to Earth. These cells retained their viability
[25] after their stratospheric journey.
Now that we know that some microorganisms their space journey the next question is: how many them fall on Earth? The estimate of the daily input of cometary debris is massive:
With a daily input of cometary debris averaging some 500 tons, the possibility of detecting infalling microbes must surely exist.
[26]
Correlated with the substantial infalling of cometary debris, the deposition of microorganisms on Earth is also massive:
Here, we demonstrate that even in pristine environments, above the atmospheric boundary layer, the downward flux of viruses ranged from 0.26 × 109 to 7 × 109 m2 per day. These deposition rates were 9–461 times greater than the rates for bacteria, which ranged from 0.3 × 107 to 8 × 107 m
2 per day
[27]
You read it right. Everyday there are about one billion viruses falling from the sky for every single square meter
[28]. To give a more commensurable example, in a country like Canada, this astounding deposition rate translates into 25 viruses that fall from the sky daily per inhabitant:
"Every day, more than 800 million viruses are deposited per square meter above the planetary boundary layer -- that's 25 viruses for each person in Canada," said University of British Columbia virologist Curtis Suttle, one of the senior authors of a paper in the International Society for Microbial Ecology Journal that outlines the findings.
[29]
Now that we know that microorganisms, including viruses, are present in both cometary material and in the higher atmosphere the questions that are arises is: where do these viruses come from? What is their origin?
The next chapter aims to provide some answers to these questions.
[1] Wickramasinghe, Chandra
et al. (2013) “Diseases From Space: Astrobiology, Viruses, Microbiology, Meteors, Comets, Evolution”
Cosmology Science Publishers
[2] Pitari, Giovanni
et al. (2016) “Impact of Stratospheric Volcanic Aerosols on Age-of-Air and Transport of Long-Lived Species”
Atmosphere 7. 149. 10.3390
[3] Wickramasinghe, 2013
[4] Aerosol particles' lifetime (such as those from volcanic eruptions) in the stratosphere, has been calculated to be 1 to 2 years
[5] DasSarma P.
et al. (2020) “Earth's Stratosphere and Microbial Life”
Curr Issues Mol Biol. 38:197-244
[6] Burdyuzha, 2006
[7] Wickramasinghe
et al. (2010) “Bacterial morphologies in carbonaceous meteorites and comet dust”
Proc. SPIE 7819
[8] 53 mi
[9] DasSarma P., 2020
[10] Wikipedia contributors (2022) “Panspermia”
Wikipedia
[11] 25 mi
[12] Shivaji, S.
et al. (2009) "Janibacter hoylei sp. nov., Bacillus isronensis sp. nov. and Bacillus aryabhattai sp. nov., isolated from cryotubes used for collecting air from upper atmosphere"
International Journal of Systematic and Evolutionary Microbiology. 59 (Pt 12): 2977–86
[13] Ibid
[14] DasSarma P.
et al. (2020) “Earth's Stratosphere and Microbial Life”
Curr Issues Mol Biol. 2020;38:197-244
[15] A group of micro-organisms that are similar to, but evolutionarily distinct from bacteria
[16] Wickramasinghe, Chandra
et al. (2010) "Bacterial morphologies in carbonaceous meteorites and comet dust"
Instruments, Methods, and Missions for Astrobiology XIII, vol. 7819, pp. 299-315
[17] 25 to 48 mi
[18] Joseph R. (2010) “Comets and Contagion: Evolution, Plague, and Diseases From Space”
Research Gate
[19] Díaz EE.
et al. (2006) “Phenotypic properties and microbial diversity of methanogenic granules from a full-scale upflow anaerobic sludge bed reactor treating brewery wastewater”
Appl Environ Microbiol. 72(7):4942-9
[20] Torosian S.
et al. (2009) “A refrigeration temperature of 4 °C does not prevent static growth of Yersinia pestis in heart infusion broth”
Canadian journal of microbiology 55. 1119-24. 10.1139
[21] Singh, O. and Gabani, P. (2011) “Extremophiles: radiation resistance microbial reserves and therapeutic implications”
Journal of Applied Microbiology 110: 851-861
[22] Hoover, R.B.
et al. (1986) “Diatoms on earth, comets, Europa and in interstellar space”
Earth Moon Planet 35, 19–45
[23] For comparison a dose of 1,000 rad is almost invariably fatal for humans
[24] Pavletić B
et al. (2022) “Spaceflight Virology: What Do We Know about Viral Threats in the Spaceflight Environment?”
Astrobiology 22(2):210-224
[25] DasSarma, S. and DasSarma, P. (2018) “Survival of microbes in Earth's stratosphere”
Current Opinion in Microbiology 43, 24-30
[26] Vladimir Burdyuzha (2006) “The Future of Life and the Future of our Civilization”
Springer
[27] Isabel Reche
et al. (2018) “Deposition rates of viruses and bacteria above the atmospheric boundary layer”
The ISME Journal
[28] 10 sqft
[29] Ibid
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