Pollen-Associated Microbiome Correlates with Pollution Parameters and the Allergenicity of Pollen

Abstract

Pollen allergies have been rapidly increasing over the last decades. Many allergenic proteins and non-allergenic adjuvant compounds of pollen are involved in the plant defense against environmental or microbial stress. The first aim of this study was to analyze and compare the colonizing microbes on allergenic pollen. The second aim was to investigate detectable correlations between pollen microbiota and parameters of air pollution or pollen allergenicity. To reach these aims, bacterial and fungal DNA was isolated from pollen samples of timothy grass (Phleum pratense, n = 20) and birch trees (Betula pendula, n = 55). With this isolated DNA, a terminal restriction fragment length polymorphism analysis was performed. One result was that the microbial diversity on birch tree and timothy grass pollen samples (Shannon/Simpson diversity indices) was partly significantly correlated to allergenicity parameters (Bet v 1/Phl p 5, pollen-associated lipid mediators). Furthermore, the microbial diversity on birch pollen samples was correlated to on-site air pollution (nitrogen dioxide (NO2), ammonia (NH3), and ozone (O3)). What is more, a significant negative correlation was observed between the microbial diversity on birch pollen and the measured NO2 concentrations on the corresponding trees. Our results showed that the microbial composition of pollen was correlated to environmental exposure parameters alongside with a differential expression of allergen and pollen-associated lipid mediators. This might translate into altered allergenicity of pollen due to environmental and microbial stress.

Bacterial microbiota associated with flower pollen is influenced by pollination type, and shows a high degree of diversity and species‐specificity

“…While pollen-associated fungi were extensively investigated, only a few studies focused on bacteria. However, these studies relied only on the cultivated fraction (Colldahl and Nilsson, 1973), amplicon libraries sequencing (Junker and Keller, 2015) or molecular fingerprinting (Obersteiner et al, 2016). Here, for the first time, cultivation-dependent, cultivation-independent and microscopy analysis of four different pollen species were performed, thus achieving the most comprehensive bacterial microbiota analysis of pollen.…”

“…It could be shown that insect-pollinated pollen has a more lipid-rich coat than wind-pollinated pollen (Edlund et al, 2004). Bacterial and fungal patterns on different pollen species (birch and timothy grass) were found to be species-specific, and the birch pollen showed higher microbial diversity than timothy grass (Obersteiner et al, 2016). However, these two pollen species have been collected from different regions, while in our work we analysed samples originating from four sampling sites within a restricted geographic area, with different pollen species sampled from the same sites.…”

“…Two recent studies indicated that flower organs harbour a unique microbiota different from that of the leaves of the same plant species and independent from environmental conditions (Junker and Keller, 2015). Recently, it could be shown for birch and timothy grass that the microbial community associated with pollen is plant species-specific (Obersteiner et al, 2016). Furthermore, pollen are a promising source of unknown bacteria, as a new genus was isolated from pollen (Jojima et al, 2004).…”

Cardosin A endocytosis mediated by integrin leads to lysosome leakage and apoptosis of epithelial cells

“…Many research has been focused on pollen-food allergy syndrome (PFAS), including pollenassociated microbiome correlates with pollution parameters and the allergenicity of pollen. [18][19][20][21][22][23][24] Whether aspartyl proteases from plant flowers could degrade the epithelial cells in the mucus layers in human nasal cavity, lung, mouth, and intestine remains unknown. The precise molecular mechanism for the degradation of human epithelial cells caused by plant aspartyl proteases warrant further investigation.…”

Emerging concepts and challenges in implementing the exposome paradigm in allergic diseases and asthma: a Practall document

“…Lack of planning in the design of urban spaces with low species biodiversity at planting, overabundance of species acting as pollen sources, exotic species prompting new allergies in the population, botanical sexism, the presence of invasive species, inappropriate garden management and maintenance activities, cross‐reactivity between phylogenetically related species and the interaction between pollen, its microbiome, and air pollutants are major causes triggering pollen allergy . In recent decades, city planning strategies have favored pollen‐producing male bushes, trees, and plants.…”