outdoor atmospheric samples, researchers were able to demonstrate that isolates
collected from the atmosphere over a landfill were able to oxidize methane in spiked
experiments conducted under cloud-like conditions (Santl-Temkiv et al. 2013).
Other types of seeps such as hydrogen-nitrogen seeps may be able to produce
atmospheric plumes capable of supporting microbial metabolism (Sano et al.
1993). Research of cloud water collected by aircraft at an altitude between ~1.4
and 3.1 km (cloud temperatures greater than 6
C) identified concentrations of
ammonia, nitrate, and dissolved organic nitrogen at ~43, ~39, and ~ 18%, respectively (Hill et al. 2007). This research noted that concentrations of bacteria in the
cloud samples averaged ~2.9 Â 10
5 m
À3 of cloudy air, that ~70% were metabolically
active, and that ammonia-oxidizing bacteria were identified in these samples (Hill
et al. 2007; Kourtev et al. 2011).
The evidence of metabolically active bacteria isolated from clouds and atmospheres associated with natural and anthropogenic gas seeps indicates the possibility
of the existence of microbial evanescent ecosystems in Earth’s atmosphere. Sources
that may load the atmosphere with terrestrial and aquatic microorganisms and
nutrients and also support these types of ecosystems include plumes originating
from volcanic eruptions, dust storms, fires, and sea spray. The optimal location for
these types of ecosystems is in the lower atmosphere where warmer temperatures
would allow metabolic rates that would be expected for a wide range of microorganisms. It may be possible that similar ecosystems exist at higher altitudes at lower
metabolic rates for known microorganisms or yet undiscovered groups of specially
adapted microorganisms. Genomic technology now exists to advance our understanding of atmospheric microbial metabolic activity and how aerosol sources affect
microbial densities and interactions by longitude, latitude, and altitude. However,
funding constraints have hindered the acquisition and analyses of high-altitude
atmospheric samples, and this has limited our ability to study and understand the
extent and constraints of microbial life in Earth’s atmosphere and those of other
planetary bodies.
Acknowledgments/Disclaimer The USGS Environmental Health Mission Area supported
the production of this article. Thanks to Tony Greco of the University of South Florida’s College of
Marine Science Electron Microscope Laboratory for assistance in acquiring the image in Fig. 5.2.
Any use of trade, firm, or product names is for descriptive purposes only and does not imply
endorsement by the US Government.
110
D. W. Griffin
collected from the atmosphere over a landfill were able to oxidize methane in spiked
experiments conducted under cloud-like conditions (Santl-Temkiv et al. 2013).
Other types of seeps such as hydrogen-nitrogen seeps may be able to produce
atmospheric plumes capable of supporting microbial metabolism (Sano et al.
1993). Research of cloud water collected by aircraft at an altitude between ~1.4
and 3.1 km (cloud temperatures greater than 6
C) identified concentrations of
ammonia, nitrate, and dissolved organic nitrogen at ~43, ~39, and ~ 18%, respectively (Hill et al. 2007). This research noted that concentrations of bacteria in the
cloud samples averaged ~2.9 Â 10
5 m
À3 of cloudy air, that ~70% were metabolically
active, and that ammonia-oxidizing bacteria were identified in these samples (Hill
et al. 2007; Kourtev et al. 2011).
The evidence of metabolically active bacteria isolated from clouds and atmospheres associated with natural and anthropogenic gas seeps indicates the possibility
of the existence of microbial evanescent ecosystems in Earth’s atmosphere. Sources
that may load the atmosphere with terrestrial and aquatic microorganisms and
nutrients and also support these types of ecosystems include plumes originating
from volcanic eruptions, dust storms, fires, and sea spray. The optimal location for
these types of ecosystems is in the lower atmosphere where warmer temperatures
would allow metabolic rates that would be expected for a wide range of microorganisms. It may be possible that similar ecosystems exist at higher altitudes at lower
metabolic rates for known microorganisms or yet undiscovered groups of specially
adapted microorganisms. Genomic technology now exists to advance our understanding of atmospheric microbial metabolic activity and how aerosol sources affect
microbial densities and interactions by longitude, latitude, and altitude. However,
funding constraints have hindered the acquisition and analyses of high-altitude
atmospheric samples, and this has limited our ability to study and understand the
extent and constraints of microbial life in Earth’s atmosphere and those of other
planetary bodies.
Acknowledgments/Disclaimer The USGS Environmental Health Mission Area supported
the production of this article. Thanks to Tony Greco of the University of South Florida’s College of
Marine Science Electron Microscope Laboratory for assistance in acquiring the image in Fig. 5.2.
Any use of trade, firm, or product names is for descriptive purposes only and does not imply
endorsement by the US Government.
110
D. W. Griffin