Abstract
The aerial surfaces of plants harbor diverse communities of microorganisms. The rising awareness concerning the potential roles of these phyllosphere microbiota for airborne pollutant remediation and plant growth promotion, advocates for a better understanding of their community structure and dynamics in urban ecosystems. Here, we characterized the epiphytic microbial communities on leaves of Platanus × hispanica trees in the city centre of Hasselt (Belgium), and the nearby forest area of Bokrijk, Genk (Belgium). We compared the influences of season, site, and air pollutants concentration variations on the tree’s phyllosphere microbiome by determining the intra- and inter-individual variation in leaf bacterial communities. High-throughput amplicon sequencing of the 16S rRNA gene revealed large variation in the bacterial community structure and diversity throughout the years but also allowed to discriminate an environment effect on community assembly. Partial drivers for this environment effect on composition can be correlated with the huge differences in ultrafine particulate matter (UFP) and black carbon on the leaves. A change in bacterial community composition was noted for trees growing in the city center compared to the natural site, and also more human-associated genera were found colonizing the leaves from the city center. These integrated results offer an original and first insight in the Platanus phyllomicrobiota, which can offer new opportunities to use phyllosphere microorganisms to enhance air pollution degradation.
Highlights
Microorganisms associated with the aerial structures of plants, otherwise known as the phyllosphere, are receiving greater attention in urban microbiome research (King, 2014)
To better understand the bacterial phyllosphere of Platanus × hispanica trees planted in urban centers and the effects which anthropogenic pressures may exert on these communities, we chose three locations of different urban density and traffic patterns from which to sample air quality and leaves
Based on a comparison with the leaves of the trees in the urban and rural areas, our results indicated that the richness and diversity of bacteria on urban Platanus × hispanica tree leaves are not significantly impacted by increased exposure to ultrafine particulate matter (UFP) and black carbon (BC) (Table 2)
Summary
Microorganisms associated with the aerial structures of plants, otherwise known as the phyllosphere, are receiving greater attention in urban microbiome research (King, 2014). An important part of future urban planning is minimizing environmental degradation for the health and safety of the residents. The “biodiversity hypothesis” connects evidence between the rise of non-communicable diseases in urbanized populations to the decrease of environmental. In 2018, 55% of the world’s population live in urban environments and this is expected to increase in the future with rising population growth (United Nations, 2018). Urban residents are more likely to be exposed to higher levels of air pollution, amongst which traffic related sources of pollution contribute an important part, and which leads to lung and cardiovascular diseases and premature death. Plans to mitigate exposure to air pollution and to promote urban green coverage for scavenging airborne pollutants (fine dust, soot particles, PAHs) each represent important efforts to combat this ubiquitous problem
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