Short-Term Temporal Variability in Airborne Bacterial and Fungal Populations

Abstract

Airborne microorganisms have been studied for centuries, but the majority of this research has relied on cultivation-dependent surveys that may not capture all of the microbial diversity in the atmosphere. As a result, our understanding of airborne microbial ecology is limited despite the relevance of airborne microbes to human health, various ecosystem functions, and environmental quality. Cultivation-independent surveys of small-subunit rRNA genes were conducted in order to identify the types of airborne bacteria and fungi found at a single site (Boulder, CO) and the temporal variability in the microbial assemblages over an 8-day period. We found that the air samples were dominated by ascomycete fungi of the Hypocreales order and a diverse array of bacteria, including members of the proteobacterial and Cytophaga-Flavobacterium-Bacteroides groups that are commonly found in comparable culture-independent surveys of airborne bacteria. Bacterium/fungus ratios varied by 2 orders of magnitude over the sampling period, and we observed large shifts in the phylogenetic diversity of bacteria present in the air samples collected on different dates, shifts that were not likely to be related to local meteorological conditions. 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.

Primary biological aerosol particles in the atmosphere: a review

“…Mancinelli and Shulls, 1978;Atlas and Bartha, 1997;Atlas and Bartha, 1997;Fuzzi et al, 1997;Kellogg and Griffin, 2006;Amato et al, 2007b;Fang et al, 2007;Fahlgren et al, 2010), whereas culture-independent techniques primarily find Gram-negative bacteria (e.g. Radosevich et al, 2002;Maron et al, 2005;Brodie et al, 2007;Despre´s et al, 2007;Fierer et al, 2008;Fahlgren et al, 2010). Independent of the choice of detection method, several general trends can be observed from ambient measurements.…”

“…nor a high species richness (in particular Basidiomycota), which may well be due to limitations of the applied PCR primers (e.g. Despre´s et al, 2007;Fierer et al, 2008;Bowers et al, 2009), although over 1500 fungal DNA sequences from 5 urban air samples were measured by Fierer et al (2008) and several dozens of filter samples of urban, rural and highalpine air were analysed by Despre´s et al (2007). Thus, careful selection and combination of multiple PCR primer pairs and other materials for the extraction and amplification of DNA obtained from aerosol samples are key elements for achieving high coverage of species richness (!300 species), as discussed in .…”

“…Studies based on DNA obtained directly from atmospheric aerosol samples offer new possibilities to identify the origin of fungal matter, independent of viability, cultivability and fragmentation (e.g. Boreson et al, 2004;Peccia and Hernandez, 2006;Fierer et al, 2008;Bowers et al, 2009;. DNAbased techniques can amplify target regions of the DNA extracted directly from atmospheric aerosol samples.…”

“…Baertsch et al, 2007;Moletta et al, 2007;Thummes et al, 2007), but these are specialised environments rich in biological material. Three aerosol studies (Despre´s et al, 2007;Fierer et al, 2008;Bowers et al, 2009) utilised polymerase chain reaction (PCR) primers capable of amplifying archaeal DNA, but were unable to amplify and detect genetic material from archaea. This may be due to limitations of the applied PCR primers and amplification conditions as described in Section 3.3.1.3.…”

Workshop on the Sources, Quantification and Health Implications of Bioaerosols Workshop Report

“…Although bioaerosols are ubiquitous in all environments, the concentration and composition of bioaerosols emitted from natural sources (e.g., animals, man, soil, plants and fungi) depends on several factors, including geographic location, weather, season and time of day Brodie et al, 2007;Fierer et al, 2008;Lee et al, 2010). There has been sufficient evidence, for example, that warm, damp and humid conditions promote the survival and growth of fungi (mold) in the indoor environment.…”