Scientific Theme: Advanced Modeling and Observing Systems

Complementary Research: Faculty Fellows Research
Temporal Variability in Airborne Microbial Populations
Noah Fierer
Funding: A.W. Mellon Foundation, NSF
Bacteria and fungi are ubiquitous in the atmosphere and represent a large proportion of total
airborne particulates. Atmospheric transport is a key mode of microbial dispersal and the
transmission of airborne plant and animal pathogens can have significant impacts on
ecosystems, human health, and agricultural productivity. Despite their importance, there
have been very few studies describing the full extent of bacterial and fungal diversity in the
atmosphere. We used a cultivation-independent molecular approach to identify the bacteria
and fungi present in air samples collected from a single site in Boulder, Colorado. We
documented shifts in the types of bacteria and fungi found in air from the site over an eight-day period to assess the
temporal variability associated with the diversity of airborne microbes and the climatic factors driving this
variability.
We found that the air samples were dominated by potentially allergenic fungi and a diverse array of bacteria,
including specific types of bacteria that are commonly found in air samples collected from across the globe.
Bacterial:fungal ratios varied by two orders of magnitude over the sampling period, and we observed large shifts in
the diversity of bacteria present in the air samples collected on different dates. We observed more phylogenetic
similarity between bacteria collected from geographically distant sites than between bacteria collected from the
same site on different days. These results suggest that outdoor air may harbor similar types of bacteria regardless of
location, and that the short-term temporal variability in airborne bacterial assemblages can be very large. We are
currently expanding on this work to further understand how airborne microorganisms vary across space and time so
we can better predict disease outbreaks (including allergenic asthma) triggered by airborne bacteria and fungi.
Figure 1. Air sampling equipment on site in northeastern
Colorado.
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Figure 2. The taxonomic composition of the
biological aerosols sampled from Boulder, CO on
five dates.