Noah Fierer
Ph.D. Ecology, University of California – Santa Barbara, 2003
Assistant Professor, Ecology and Evolutionary Biology Department
E-mail: fierer@cires.colorado.edu
Web: EBIO
Fierer Research Group
Office: CIRES 1B56
Phone: 303-492-5615
Research Interests
Microbial ecology. Terrestrial ecosystem ecology. Microbial biogeography. Impact of global change factors on microbial communities and processes.
Current Research: Microbial Life in the Atmosphere
Bacteria are abundant in the atmosphere with the near-surface atmosphere containing more than 106 bacterial cells per cubic meter of air. Atmospheric transport is a key mode of microbial dispersal, and the transmission of airborne plant and animal pathogens can significantly affect ecosystems, agriculture, and human health. For example, recent work implicates bacteria found in outdoor air—rather than pollen or fungi—as being one of the dominant triggers of allergies and asthmatic reactions in many locations. In addition, recent evidence suggests that airborne bacteria may be able to alter precipitation events by facilitating atmospheric ice nucleation and cloud condensation. If this is valid, it would suggest a novel linkage between the land surface (the source of bacterial cells) and the atmosphere, with micron-sized organisms having far-reaching impacts on local and regional atmospheric conditions.
The dominant bacterial phyla and sub-phyla found in air samples
collected from across the three land-use types in the Colorado Front
Range: forest (n = 5), agricultural (n = 5), and suburban (n = 5). Error bars
indicate ± 1 standard error of the mean. (click image for full size)
Graduate student Bob Bowers with air sampling equipment at an agricultural field east of Boulder.
Our ongoing work addresses three fundamental questions regarding bacteria in the atmosphere: 1) What is the full extent of bacterial diversity in the nearsurface atmosphere?, 2) How does the abundance, composition, and diversity of airborne bacterial communities change across land-use types?, and 3) How abundant are high-temperature bacterial ice nucleators in the atmosphere?
During the past year, we have been addressing these questions with aseries of studies conducted across the Colorado Front Range. We have focused on 15 sites in three land-use types that dominate the Front Range area (urban/suburban, agricultural fields, and forests). We used a range of molecular techniques, including high-throughput pyrosequencing, to characterize the bacterial communities in the collected air samples. We found that the atmosphere over each land-use type harbored significantly different bacterial communities, and we could link these shifts in the bacterial communities to changes in the relative importance of soil (dust) versus leaf inputs of bacteria to the atmosphere. We also found that the atmosphere above agricultural fields has far higher concentrations of bacterial ice nucleators than the other land-use types, and we link these airborne ice nucleators to those bacteria commonly found on wheat and other agricultural crops. Finally, we show that bacterial diversity in the atmosphere is far higher than expected, with hundreds of bacterial species per cubic meter of air.
We are currently expanding on this work to examine airborne bacterial diversity across broader spatial and temporal gradients. We are also investigating whether we may be able to use airborne bacteria to track the sources of air parcels as they move across the continental United States.
