Yeasts prefer daycares and molds prefer private homes

Indoor fungi can cause negative health effects due to the production of toxins or volatiles that trigger the immune system of the occupants. To what degree indoor fungi (mycobiomes) differ between buildings with different usage is poorly known. Here, we compare the indoor mycobiomes in 123 childrens daycare centers and 214 private homes throughout Norway, as revealed by metabarcoding of DNA extracted from dust samples collected by community scientists. Although the fungal richness per se was similar in dust samples from daycares and homes, the fungal community composition differed. Yeast fungi, distributed mainly across the orders Saccharomycetales, Filobasidiales and Tremellales, were proportionally more abundant in the daycares, while filamentous fungi, including spore-producing molds such as Aspergillus, Penicillum and Cladosporium, were relatively more abundant in homes. Number of occupants, which is considerably higher in daycares, correlated significantly with the fungal community shift. We hypothesize that the density of occupants and their age distribution drive the systematic difference of yeasts and filamentous fungi in the two building types. ImportanceWorldwide, people spend most of their time indoors; in their homes, workplaces, schools and daycares. The indoor environment can thus largely influence our health. In this study, we revealed that number of occupants and possibly their age distribution are important explanatory variables for the fungal communities of the indoor environments in homes and daycares. Knowledge of these communities are important for further studies on how fungal diversity affect our health.