Department of Environmental Sciences
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Seminar Abstracts
Environmental Sciences Seminar Abstract            

  Tracking The Sources And Origins Of Microbial Communities Suspended In Indoor And Outdoor Air
Jordan Peccia
Yale University

The goal of this research was to determine the origins and population characteristics of airborne bacteria in an occupied classroom. We hypothesize that human occupancy is the dominant source of indoor airborne bacteria and that what is airborne reflects a combination of surface resuspension plus active shedding and/or emissions from humans. In addition to monitoring PM10 airborne mass and bacterial genome concentrations under occupied and unoccupied scenarios, the origins of the airborne biological material were determined by producing 16s rDNA-based phylogenetic libraries of indoor air and potential indoor air sources including floor dust, outdoor air, human hands, and human saliva. Bioinformatic tools were used to quantitatively compare these libraries with each other and to also compare these libraries with databases of the human microbiome or soil and plant associated microbiota.

Quantitative PCR-monitoring of total airborne bacteria in PM10 aerosol fractions during occupied and unoccupied conditions demonstrated a greater than 10 times increase in airborne bacteria genomes during occupancy. Principal component analysis based on phylogenetic similarities in populations of potential sources (human hands and saliva, floor dust, outdoor air, ventilation ducts) indicates that the dominant source of this increased load is resuspended floor dust. Floor dust populations show close similarities with indoor air populations and significant differences with other sources. A more detailed observation of the ecology in indoor air indicates that many of the prominent phylogenetic groups that account for more than 30% of the abundance in indoor air during occupancy can be traced to taxa that are highly enriched in human skin, hair, and nostrils (e.g. Propionibacterineae, Staphylococcus, and Corynebacterineae). These results suggest that in densely occupied environments, exposure to microbes from human sources can commonly occur through inhalation.


Last updated: 04/26/2011