Biodiversity of pollen in indoor air samples as revealed by DNA metabarcoding

16 June 2017

Korpelainen, Helena; Pietiläinen, Maria

We conducted DNA metabarcoding (based on the nuclear ITS2 region) to characterize indoor pollen samples (possibly accompanied by other plant fragments) and to discover whether there are seasonal changes in their taxonomic diversity. It was shown that DNA metabarcoding has potential to allow a good discovery of taxonomic diversity. The numbers of spermatophyte families and genera varied greatly among sampling sites (pooled results per building) and times, between 9-40 and 10-66, respectively. Comparable Shannon’s diversity indices equaled 0.33-2.76 and 0.94-3.16. The total number of spermatophyte genera found during the study was 187, of which 43.9, 39.6, 7.5 and 9.1% represented wild, garden/crop and indoor house plants, and non-domestic fruit or other plant material, respectively. Comparable proportions of individual sequences equaled 77.4, 18.8, 2.7 and 1.1%, respectively. When comparing plant diversities and taxonomic composition among buildings or between seasons, no obvious pattern was detected, except for the second summer, when pollen coming from outdoors was highly dominant and the proportions of likely allergens, birch, grass, alder and mugwort pollen, were very high. The average pairwise values of SørensenChao indices that were used to compare similarities for taxon composition between samples among the samples from the two university buildings, two nurseries and farmhouse equaled 0.514, 0.109, 0.564, 0.865 and 0.867, respectively, while the mean similarity index for all samples was 0.524. Cleaning frequency may strongly contribute to the observed diversity. The discovery of considerable diversities, including pollen coming from outside, in both winter and summer shows that substantial amounts of pollen produced in summer enter buildings and stay there throughout the year.