The three mentioned objectives were coupled to three scientific work packages (WPs):
WP1: Sequence database for cultivable Scandinavian indoor fungi. A collection of fungal isolates were molecularly characterized by DNA (Sanger) sequencing of their ribosomal inter transcribed spacers (ITS). This database included 200 airborne fungi from kindergartens and 22 material-colonising fungi from private houses. This library was very useful to improve the taxonomic assignment of the HTS data from the environmental samples studied in the WPs 2 and 3.
WP2: Local in-depth survey of the indoor mycobiome. Two different studies were conducted: (Study 2.1) spatiotemporal monitoring of two kindergartens, investigating the mycobiome variation in different parts of buildings during a one-year period; and (Study 2.2) the characterization of the indoor mycobiome associated with mould-damaged buildings (22 houses in Oslo), comparing the fungi growing on different damaged materials and their influence on other parts of buildings.
WP3: Large-scale survey of the Norwegian indoor mycobiome. We organized a large citizen science dust sampling campaign in 290 houses throughout Norway coupled to the subsequent DNA metabarcoding analyses of the mycobiomes (Study 3).
Overview of main MycoIndoor results achieved so far:
Although we are still working on the final data analyses of the local surveys (WP2), the preliminary results of study 2.1 showed that sampling location and sampling time were the main contributors to the variation in the fungal community composition in the monitored kindergartens. The sampling location factor was a relevant determinant showing different community composition depending on the kindergarten compartment sampled (outdoor vs. indoor). We also found clear seasonal patterns in the variation of fungal communities, especially evident for outdoor samples. Some occupant characteristics (number of children/adults and their activities) were also relevant determinants of indoor mycobiomes in kindergartens, acting as fungal indoor sources. The expected knowledge from the study 2.2 includes: a more complete picture of fungi associated with material deterioration in houses, comparison between classical (microscopy) and DNA-based approaches, and the influence of mould problems on the indoor air quality and the human exposure in different house compartments.
The large-scale survey (WP3) was able to unravel the main factors shaping the indoor mycobiomes throughout Norway. A relatively low overall variation (15%) in the fungal community composition was explained by the studied variables (outdoor environment, building and occupants). However, all variables had a significant influence. Overall, after excluding the key influence of the house compartment factor (7.66% of the variation), results clearly demonstrated that regional-scale climate is the most important driver of indoor mycobiomes (4.18%). Occupant and building factors also showed significant influences but with much lesser extents (1.44% and 1.11%, respectively). In agreement with some previous studies, we observed a consistent pattern of higher fungal richness and alpha diversity in indoor than outdoor samples, and slightly higher alpha diversity in the north region. The fungal composition in the outdoor samples was clearly different from that of the indoor samples. As reported in previous studies, fungi from outdoor air were relevant contributors to the indoor mycobiomes. However, a comparison on a house-by-house basis revealed that only 15% of detected species were shared between outdoor and indoor samples, while 75% appeared uniquely in one of the house compartments (outside, living room and bathroom). Therefore, our study confirmed the importance of fungal indoor sources such as occupants, organic matter and potential mould growth on surfaces.
