Environmental DNA analyses reveal links between abundance and composition of airborne grass pollen and population scale respiratory health

Abstract

<p><b>Background:</b> A growing interest to fungal spores is observed in Allergology during recent years. Some of them such as Alternaria are well-known factors of both persistent and intermittent allergic rhinitis. As fungi are ubiquitous, they may inhabit nearly every substrate including different parts of flowering plants. In addition, as we observed in recent years, pollen can carry fungal spores on its surface. As we have already shown, Alternaria and other spores can be associated with Ambrosia pollen. This might be practically important as simultaneous exposure to different allergen types can promote polysensitisation of atopic patients. Therefore, the aim of our study was to check pollen of early flowering alder for presence of fungal spores and compare the data with the fungal spore spectrum found on the ragweed pollen.</p> <p><b>Method:</b> Alnus catkins were selected on the shores of Sotskij Lake on March 14, 2020. Sterile gloves were used to reduce possible contamination of the catkings by external factors. Petri dishes with imprints of cross sections of catkins with pollen were cultured on Sabouraud dextrose agar from 16.03.2020. After germination of fungal spores, further determination of fungal colonies was performed by light microscopy based on their morphological features at magnifications of 4 ×, 100 × and 400 ×. A preservative, 1% lactic acid, was also used to prepare the samples.</p><p><b>Results:</b> Cladosporium (38 %), yeast colonies (up to 30%), non-sporulating fungi and Aspergillus dominated on the Alnus pollen. While on the cultured Ambrosia pollen surface’ Penicillum was prevalent (53 %). Yeast fungi (23%), Cladosporium (5%), non-nonsporulating fung’al colonies (5%), Aspergillus (4%), Arthrinium (3%) and Alternaria (2 %) followed them. Using molecular sensitization data for Ukraine, we found that 40.45% of tested patients were sensitive to alder pollen. Almost 60 %, namely 59.7% of them, were sensitive to Alternaria at the same time, 27.4% – to Aspergillus and 1.7% – to Cladosporium.</p><p><b>Conclusion:</b> Thus, pollen of alder and ragweed could transfer fungal spores on its surface. Therefore, inhaling pollen, people can experience allergy symptoms caused by fungal spores on its surface. Other people, which are not sensitive to fungi yet, may develop such sensitisation. The composition of fungal contamination for different types of pollen may be different, taking into account different environmental conditions for plant growth and different timing of their pollination.</p>