Atmosphere Is Home To Substantial Number Of Microorganisms
January 29, 2013

Bugs In The Troposphere! Researchers Find Microorganisms In The Atmosphere

[ Watch the Video: What is Bacteria? ]

Alan McStravick for - Your Universe Online

In 2010, a NASA DC-8 soared high up into the troposphere to collect air samples in order to study air masses associated with tropical storms. What they found was quite surprising. Bugs - microorganisms actually - in the troposphere.

The troposphere is the portion of the Earth´s atmosphere that extends from ground level up to approximately 12 miles above sea level, and apparently it is home to a significant number of living microorganisms, most notably, bacteria. The fact the samples were collected in both the middle and upper troposphere is what makes this first-of-its-kind study most interesting.

While their presence was an exciting find, it is still unknown whether or not the microorganisms actually call this area home, perhaps adhering themselves to carbon compounds known to be in this area, or if they were simply lofted there from the Earth´s surface.

Atmospheric scientists found the results particularly interesting because they hypothesize the microorganisms could play a role in forming ice that may impact global weather and climate. Additionally, pathologists are interested in determining if these bacteria undergo long-distance transport around the globe. This would be an important find, helping to create future disease transmission models.

NASA's Genesis and Rapid Intensification Processes (GRIP) program, which studies low- and high-altitude air masses associated with tropical storms, was the means by which air samples were collected. Collection was performed over both land and water, including the Caribbean Sea and portions of the Atlantic Ocean. Samples were collected before, during and after two major tropical hurricanes, Earl and Karl.

"We did not expect to find so many microorganisms in the troposphere, which is considered a difficult environment for life," said Kostas Konstantinidis, an assistant professor in the School of Civil and Environmental Engineering at the Georgia Institute of Technology. "There seems to be quite a diversity of species, but not all bacteria make it into the upper troposphere."

The research team designed a specialized filter meant for the collection of particles, including microorganisms. The collections were taken from outside air that entered the aircraft´s sampling probes. Analysis, requiring the utilization of genomic techniques including polymerase chain reaction and gene sequencing, was performed on samples collected in the filters. These genomic techniques allowed the researchers to detect and estimate the quantities of the microorganisms. Previously, this would have required the use of conventional cell-culture techniques.

When the aircraft pulled samples over land, the samples consisted primarily of terrestrial bacteria. The samples collected over water, conversely, were comprised of mostly marine bacteria. Researchers did note there was strong evidence to support the idea that hurricanes played an important role in the distribution and dynamics of microorganism populations.

Bacteria, according to the study, represented an average of 20 percent of the total particles that were detected. They were typically in the size range of .25 to 1 microns in diameter. In all, 17 individual bacteria taxa were detected. Some of the collected bacteria is, they determined, capable of metabolizing the carbon compounds that are so prevalent in the atmosphere — such as oxalic acid.

According to Athanasios Nenes, professor in the Georgia Tech School of Earth and Atmospheric Sciences and School of Chemical and Biomolecular Engineering, the impact on cloud formation by these microorganisms could be significant. Prior to this study, there had been no conclusive evidence identifying bacteria possibly supplementing the abiotic particles that normally serve as nuclei for the formation of ice crystals.

"In the absence of dust or other materials that could provide a good nucleus for ice formation, just having a small number of these microorganisms around could facilitate the formation of ice at these altitudes and attract surrounding moisture," Nenes said. "If they are the right size for forming ice, they could affect the clouds around them."

It is believed the bacteria and other microorganisms make their journey skyward in much the same way dust and sea salt is vaulted into the troposphere.

“When sea spray is generated, it can carry bacteria because there are a lot of bacteria and organic materials on the surface of the ocean,” according to Nenes.

The entire research team was comprised of microbiologists, atmospheric modelers and environmental researchers. They utilized the latest technologies available for studying the DNA of the bacteria samples collected. Future study, according to the team, will likely focus on determining if there are certain strains of bacteria that are better suited for survival at altitude. Additionally, they want to gain an understanding on the role that is played by the microorganisms and learn if the samples collected are able to perform metabolic functions in the troposphere.

"For these organisms, perhaps, the conditions may not be that harsh," said Konstantinidis. "I wouldn't be surprised if there is active life and growth in clouds, but this is something we cannot say for sure now."

While previous research studies gathered their biological samples from both mountain and snow samples, this study, collected from a jet aircraft, required the team to formulate a novel experimental setup. The researchers also had to create a protocol for the extraction of DNA from the limited levels of biomass they collected. Their sample sizes were far lower than what researchers will typically extract from soils or lakes.

"We have demonstrated that our technique works, and that we can get some interesting information," Nenes said. "A big fraction of the atmospheric particles that traditionally would have been expected to be dust or sea salt may actually be bacteria. At this point we are just seeing what's up there, so this is just the beginning of what we hope to do."

The team received funding from several different sources. Among them were grants and fellowships from NASA, the US Department of Education, and the National Science Foundation.

Research findings have are published in the Proceedings of the National Academy of Sciences.