Spatiotemporal Variation of the Indoor Mycobiome in Daycare Centers

Abstract

Background: Children spend considerable time in daycare centers in parts of the world, and are exposed to the indoor micro- and mycobiomes of these facilities. The level of exposure to microorganisms varies within and between buildings, depending on occupancy, climate and season. In order to evaluate indoor air quality, and the effect of usage and seasonality, we investigate the spatiotemporal variation in the indoor mycobiomes of two daycare centers. We collected dust samples from different rooms throughout a year and analyzed their mycobiomes using DNA metabarcoding. Results: The fungal community composition in rooms with limited occupancy (auxiliary rooms) was similar to the outdoor samples, and clearly different from the rooms with higher occupancy (main rooms). The main rooms had higher abundance of Ascomycota, while the auxiliary rooms contained comparably more Basidiomycota. We observed a strong seasonal pattern in the mycobiome composition, mainly structured by the outdoor climate. Most markedly, basidiomycetes of the orders Agaricales and Polyporales, mainly reflecting typical outdoor fungi, were more abundant during summer and fall. In contrast, ascomycetes of the orders Saccharomycetales and Capnodiales were dominant during winter and spring. Conclusions: Our findings provide clear evidences that the indoor mycobiome in daycare centers are structured by occupancy as well as outdoor seasonality. We conclude that the temporal variability should be accounted for in indoor mycobiome studies and in the evaluation of indoor air quality of buildings.

The indoor mycobiome of daycare centers is affected by occupancy and climate

“…Interestingly, in our recent study on seasonality of the indoor mycobiome, the indoor environment was more influenced by the outdoor fungal diversity during summer and fall (10). Thus, as the citizen scientists in the present study sampled during early spring, we may have detected a stronger influence of indoor variables compared to e.g.…”

“…In line with this, it has previously been shown that the concentration of fungi in daycare centers is higher compared to homes (9). In several studies, the outdoor environment has been reported as the main source of indoor fungi (10)(11)(12)(13) due to the influx of spores through windows, entrances and the ventilation system. Hence, the vegetation and climate that structure the outdoor fungi will indirectly also structure the indoor mycobiome (11).…”

“…For the current study, dust samples were obtained during a relative short time window during the spring 2018. From other studies, we know there is an extensive temporal variability (10), which is not accounted for here. Moreover, sampling at approximately the same time throughout Norway, a country that spans a wide range of latitudes and longitudes, implies that the outdoor climate, vegetation and fungal communities are in different (phenological) growth phases.…”

“…DNA extraction and metabarcoding library preparation were performed according to Estensmo et al (10). Briefly, samples were thawed at 70 °C, followed by an incubation of 10 minutes at the same temperature and homogenized for 2 × 1 min at 30 Hz using the TissueLyser.…”

“…DNA metabarcoding, based on highthroughput sequencing of PCR amplified markers, is established as an effective approach to survey fungal communities (21). In buildings, DNA metabarcoding of dust samples, integrating spores and hyphal remains that have accumulated over time, has proven to be an effective mean for exploring the indoor mycobiome (10,12,(22)(23)(24). However, it might be difficult to get access and obtain samples from a representative number of buildings.…”