Contribution of Vegetation to the Microbial Composition of Nearby Outdoor Air

Abstract

Given that epiphytic microbes are often found in large population sizes on plants, we tested the hypothesis that plants are quantitatively important local sources of airborne microorganisms. The abundance of microbial communities, determined by quantifying bacterial 16S RNA genes and the fungal internal transcribed spacer (ITS) region, in air collected directly above vegetation was 2- to 10-fold higher than that in air collected simultaneously in an adjacent nonvegetated area 50 m upwind. Nonmetric multidimensional scaling revealed that the composition of airborne bacteria in upwind air samples grouped separately from that of downwind air samples, while communities on plants and downwind air could not be distinguished. In contrast, fungal taxa in air samples were more similar to each other than to the fungal epiphytes. A source-tracking algorithm revealed that up to 50% of airborne bacteria in downwind air samples were presumably of local plant origin. The difference in the proportional abundances of a given operational taxonomic unit (OTU) between downwind and upwind air when regressed against the proportional representation of this OTU on the plant yielded a positive slope for both bacteria and fungi, indicating that those taxa that were most abundant on plants proportionally contributed more to downwind air. Epiphytic fungi were less of a determinant of the microbiological distinctiveness of downwind air and upwind air than epiphytic bacteria. Emigration of epiphytic bacteria and, to a lesser extent, fungi, from plants can thus influence the microbial composition of nearby air, a finding that has important implications for surrounding ecosystems, including the built environment into which outdoor air can penetrate.IMPORTANCE This paper addresses the poorly understood role of bacterial and fungal epiphytes, the inhabitants of the aboveground plant parts, in the composition of airborne microbes in outdoor air. It is widely held that epiphytes contribute to atmospheric microbial assemblages, but much of what we know is limited to qualitative assessments. Elucidating the sources of microbes in outdoor air can inform basic biological processes seen in airborne communities (e.g., dispersal and biogeographical patterns). Furthermore, given the considerable contribution of outdoor air to microbial communities found within indoor environments, the understanding of plants as sources of airborne microbes in outdoor air might contribute to our understanding of indoor air quality. With an experimental design developed to minimize the likelihood of other-than-local plant sources contributing to the composition of airborne microbes, we provide direct evidence that plants are quantitatively important local sources of airborne microorganisms, with implications for the surrounding ecosystems.

Ecological patterns of seed microbiome diversity, transmission, and assembly

“…Proving the mode of transmission and determining transmission rates are technically challenging, as many members of the seed microbiota overlap with microorganisms that are also commonly detected in rhizosphere soils, bulk soils, plant systemic tissue, and air [10,39,[48][49][50][51]. Thus, analysis of overlap among microbiota members across plant compartments or generations planted in the field is not sufficient to prove vertical transmission, even if seeds are specifically investigated.…”

Assembly of seed-associated microbial communities within and across successive plant generations

“…Other variables such as the type of cultivated plants that surrounded the experimental plots could also contribute to observed variation in seed community composition. Recent work indicates that emigration of epiphytic bacteria and fungi from plants surfaces are important local sources of airborne micro-organisms (Lymperopoulou et al 2016). Although the same experimental plot was employed over the course of this study, other cultivated plant species in the immediate vicinity of the radish plants were not controlled between the different years.…”

Quantitative Genetic Analysis of the Maize Leaf Microbiome

“…This is in line with other studies that show little correlation between soil and leaf microbial communities, especially later in the season (such as when these samples were taken) (Kim et al 2012;Copeland et al 2015) . Wind dispersal from other plants appears to play a strong role in phyllosphere bacterial community dynamics (S. E. Lindow and Andersen 1996;Lymperopoulou, Adams, and Lindow 2016) , so that the local soil may not even serve as the inoculum for much of the phyllosphere community.…”