Abstract
Urban green space provides health benefits for city dwellers, and new evidence suggests that microorganisms associated with soil and vegetation could play a role. While airborne microorganisms are ubiquitous in urban areas, the influence of nearby vegetation on airborne microbial communities remains poorly understood. We examined airborne microbial communities in parks and parking lots in Eugene, Oregon, using high-throughput sequencing of the bacterial 16S rRNA gene on the Illumina MiSeq platform to identify bacterial taxa, and GIS to measure vegetation cover in buffer zones of different diameters. Our goal was to explore variation among highly vegetated (parks) versus non-vegetated (parking lots) urban environments. A secondary objective was to evaluate passive versus active collection methods for outdoor airborne microbial sampling. Airborne bacterial communities from five parks were different from those of five parking lots (p=0.023), although alpha diversity was similar. Direct gradient analysis showed that the proportion of vegetated area within a 50m radius of the sampling station explained 15% of the variation in bacterial community composition. A number of key taxa, including several Acidobacteriaceae were substantially more abundant in parks, while parking lots had higher relative abundance of Acetobacteraceae. Parks had greater beta diversity than parking lots, i.e. individual parks were characterized by unique bacterial signatures, whereas parking lot communities tended to be similar to each other. Although parks and parking lots were selected to form pairs of nearby sites, spatial proximity did not appear to affect compositional similarity. Our results also showed that passive and active collection methods gave comparable results, indicating the “settling dish” method is effective for outdoor airborne sampling. This work sets a foundation for understanding how urban vegetation may impact microbial communities, with potential implications for designing neighborhoods and open space systems that foster better human health.
Highlights
Human well-being in urban areas is linked to the abundance and degree of access to nearby green space (e.g., Maas 2006; Maas et al 2009; Villeneuve et al, 2012; Mitchell and Popham 2007; Dadvand et al 2012; Donovan et al 2013)
We know that urban green space has significant health benefits, we do not know the exact mechanism(s) through which those benefits arise
By 2050, the world population is expected to reach 9.3 billion and all population growth in the 35 years is projected to occur in urban areas, bringing the percentage of people living in cities to about 66% (U.N., 2012)
Summary
Human well-being in urban areas is linked to the abundance and degree of access to nearby green space (e.g., Maas 2006; Maas et al 2009; Villeneuve et al, 2012; Mitchell and Popham 2007; Dadvand et al 2012; Donovan et al 2013). Over the past few centuries our lifestyles have shifted dramatically (indoor living, antibiotic use, processed food, chemical treatment of water, etc.) and, in the process, this has altered the abundance, diversity, and composition of the microbial communities to which we are exposed on a daily basis (Blaser and Falkow 2009) While these shifts in lifestyle have been associated with reduced incidence of many diseases, greater longevity, and other benefits, it is widely recognized that early life immunological experiences, including exposures to various environmental substances as well as the lack of exposures, are associated with the development of later life immune-mediated disease, such as asthma, allergy and other inflammatory disorders (Russell et al 2012; Rook, 2013; Ege et al 2012)
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