Ridwan Hossain
We know that our planet is infested with bacteria and that they play major roles in the earth’s ecosystem. For instance, nitrogen-fixing bacteria enable the nitrogen cycle that is essential for the protein-based life forms on earth, while cyanobacteria in the ocean are responsible for a large proportion of atmospheric carbon fixation. Fascinatingly, thanks to a string of studies over the past decade, we are learning that bacteria play a part in our weather system as well.
To understand how that works we need to think about how precipitation occurs. In our planet’s water cycle, water is taken up into the atmosphere by evaporation, and this in turn later comes down as rain, hail, or snow. Scientists have realized that a huge number of bacteria is also taken up into the atmosphere along with the water. And it turns out that while they are up there, the bacteria play an important role in precipitation.
Some specific types of bacteria, found largely among Gammaproteobacteria, act as ice nuclei. Ice nucleation is when something acts as the nucleus for the formation of ice around it. Such bacteria have specific proteins on their surfaces which result in the formation of ice a lot more rapidly and at higher temperatures than would otherwise occur. This often damages plants by promoting the formation of frost, but when these ice-nucleating bacteria are present in the atmosphere, the water in the atmosphere becomes rapidly condensed into ice. When they become too heavy to keep floating in the sky, they fall as rain, snow or hail, depending on temperatures closer to the surface.
Bibliography:
Ridwan is a junior at IUB whose
dream is to be a renowned mad scientist. He will be a Nobel laureate.
Junior
School of Life Sciences
Independent University, Bangladesh
March 23rd, 2019
We know that our planet is infested with bacteria and that they play major roles in the earth’s ecosystem. For instance, nitrogen-fixing bacteria enable the nitrogen cycle that is essential for the protein-based life forms on earth, while cyanobacteria in the ocean are responsible for a large proportion of atmospheric carbon fixation. Fascinatingly, thanks to a string of studies over the past decade, we are learning that bacteria play a part in our weather system as well.
To understand how that works we need to think about how precipitation occurs. In our planet’s water cycle, water is taken up into the atmosphere by evaporation, and this in turn later comes down as rain, hail, or snow. Scientists have realized that a huge number of bacteria is also taken up into the atmosphere along with the water. And it turns out that while they are up there, the bacteria play an important role in precipitation.
Some specific types of bacteria, found largely among Gammaproteobacteria, act as ice nuclei. Ice nucleation is when something acts as the nucleus for the formation of ice around it. Such bacteria have specific proteins on their surfaces which result in the formation of ice a lot more rapidly and at higher temperatures than would otherwise occur. This often damages plants by promoting the formation of frost, but when these ice-nucleating bacteria are present in the atmosphere, the water in the atmosphere becomes rapidly condensed into ice. When they become too heavy to keep floating in the sky, they fall as rain, snow or hail, depending on temperatures closer to the surface.
Ice-nucleating bacteria promote frost formation on plants. ASM
Just how much more rain is produced by these ice-nucleating bacteria? A 2012 study tried to tackle this question using a modeling approach [1]. The authors of the study employed the BRAMS (Brazilian Regional Atmospheric Model System) model, which is typically used for simulating weather conditions based on environmental parameters like pressure, temperature, and humidity. They ran simulations using atmospheric data collected using a radiosonde on a typical summer day in Sao Paulo City to predict ice crystal formation, precipitable ice mass, and rainfall, among other variables under different varying environmental conditions. In these simulations, they incorporated estimates of the concentration of the ice-nucleating bacteria Pseudomonas syringae from previous studies, to see to what extent their presence would affect precipitation. According to their simulations, ice-nucleating bacteria being present would be expected to reduce the percentage of rainfall by about 8%. The amount of hail and snow, on the other hand, would see massive increases. Snow, for instance, showed an increase of over 200% in most of the simulations.
As ice-containing structures and the friction between them in the clouds play an important role in the making of lightning they also wanted to find out if the presence of ice-nucleating bacteria may increase the amount of lightning being generated. Unsurprisingly, they saw a massive increase in the lightning rate due to the presence of ice-nucleating bacteria in their simulations. While this study exclusively used simulations, the results are consistent with data from experimental cloud chambers. But the simulations are limited by the use of estimates for the numbers of only one type of ice-nucleating bacteria.
Other studies since then have tried to quantify the diversity of bacteria, ice-nucleating or not, in the atmosphere. A 2013 study [2] attempted to do this for the upper troposphere, and also sought to find associations with weather patterns. The authors of the study collected bacterial samples from the upper troposphere before and after two hurricanes. Sequencing of pre-hurricane samples showed the presence of many more types of bacteria than previously estimated, with many appearing to be well-adapted to the upper troposphere. The majority of the bacteria in the upper troposphere appeared to be aquatic, and the hurricanes resulted in the introduction of a large number of new bacterial species.
The bacterial particles were found to be a major constituent of atmospheric aerosols, which suggests that the dynamic microbiome of the atmosphere may have major roles to play in weather cycles.
A more recent study [3] attempted to quantify ice-nucleating bacteria in precipitation. Previous studies had shown that ice-nucleating bacteria mostly belong to the Gammaproteobacteria class of bacteria, but in this study they identified additional groups of bacteria acting as ice-nucleating agents. Notably, they identified the first known ice-nucleating Gram-positive bacteria. These bacteria are distantly related to the Gram-negative Gammaproteobacteria, suggesting that ice nucleation evolved at least twice in the evolutionary history of bacteria. This leads to speculation over whether this trait was adaptive. It is not inconceivable that the bacteria evolved to nucleate ice to rapidly exit the harsh conditions of the atmosphere as precipitation.
While this field is still in its infancy, these and other studies have established that bacteria are abundant in the atmosphere, and they are likely to play a significant role in the precipitation system. With climate change affecting the diversity of organisms from all branches of life, it is important to understand what roles bacteria in the atmosphere play, which bacteria are mainly involved, and how these functions may be affected by disruption of the atmospheric microbiome.
As ice-containing structures and the friction between them in the clouds play an important role in the making of lightning they also wanted to find out if the presence of ice-nucleating bacteria may increase the amount of lightning being generated. Unsurprisingly, they saw a massive increase in the lightning rate due to the presence of ice-nucleating bacteria in their simulations. While this study exclusively used simulations, the results are consistent with data from experimental cloud chambers. But the simulations are limited by the use of estimates for the numbers of only one type of ice-nucleating bacteria.
Other studies since then have tried to quantify the diversity of bacteria, ice-nucleating or not, in the atmosphere. A 2013 study [2] attempted to do this for the upper troposphere, and also sought to find associations with weather patterns. The authors of the study collected bacterial samples from the upper troposphere before and after two hurricanes. Sequencing of pre-hurricane samples showed the presence of many more types of bacteria than previously estimated, with many appearing to be well-adapted to the upper troposphere. The majority of the bacteria in the upper troposphere appeared to be aquatic, and the hurricanes resulted in the introduction of a large number of new bacterial species.
The bacterial particles were found to be a major constituent of atmospheric aerosols, which suggests that the dynamic microbiome of the atmosphere may have major roles to play in weather cycles.
A more recent study [3] attempted to quantify ice-nucleating bacteria in precipitation. Previous studies had shown that ice-nucleating bacteria mostly belong to the Gammaproteobacteria class of bacteria, but in this study they identified additional groups of bacteria acting as ice-nucleating agents. Notably, they identified the first known ice-nucleating Gram-positive bacteria. These bacteria are distantly related to the Gram-negative Gammaproteobacteria, suggesting that ice nucleation evolved at least twice in the evolutionary history of bacteria. This leads to speculation over whether this trait was adaptive. It is not inconceivable that the bacteria evolved to nucleate ice to rapidly exit the harsh conditions of the atmosphere as precipitation.
While this field is still in its infancy, these and other studies have established that bacteria are abundant in the atmosphere, and they are likely to play a significant role in the precipitation system. With climate change affecting the diversity of organisms from all branches of life, it is important to understand what roles bacteria in the atmosphere play, which bacteria are mainly involved, and how these functions may be affected by disruption of the atmospheric microbiome.
Bibliography:
1. Gonçalves, F. L. T., Martins, J. A., Albrecht, R. I.,
Morales, C. A., Silva Dias, M. A., & Morris, C. E. (2012). Effect of
bacterial ice nuclei on the frequency and intensity of lightning activity
inferred by the BRAMS model. Atmospheric Chemistry and Physics, 12(13),
5677–5689. https://doi.org/10.5194/acp-12-5677-2012
2. DeLeon-Rodriguez, N., Lathem, T. L., Rodriguez-R, L. M., Barazesh, J. M., Anderson, B. E., Beyersdorf, A. J., … Konstantinidis, K. T. (2013). Microbiome of the upper troposphere: species composition and prevalence, effects of tropical storms, and atmospheric implications. Proceedings of the National Academy of Sciences of the United States of America, 110(7), 2575–2580. https://doi.org/10.1073/pnas.1212089110
2. DeLeon-Rodriguez, N., Lathem, T. L., Rodriguez-R, L. M., Barazesh, J. M., Anderson, B. E., Beyersdorf, A. J., … Konstantinidis, K. T. (2013). Microbiome of the upper troposphere: species composition and prevalence, effects of tropical storms, and atmospheric implications. Proceedings of the National Academy of Sciences of the United States of America, 110(7), 2575–2580. https://doi.org/10.1073/pnas.1212089110
3. Failor, K. C., Schmale, D. G., Vinatzer, B. A., &
Monteil, C. L. (2017). Ice nucleation active bacteria in precipitation are
genetically diverse and nucleate ice by employing different mechanisms. ISME
Journal, 11(12), 2740–2753. https://doi.org/10.1038/ismej.2017.124
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