Evgenia Dikareva (Maastricht University Medical Center)

Summary of presentation:
Introduction: Playing outdoors is essential for infants’ development. During outdoor play, children come into frequent contact with soil and its microbes. Emerging evidence suggests that exposure to nature-borne microbes can enrich infants’ gut microbiota, which in turn may support health, for example by promoting immune development. Nonetheless, the specific composition of microbial communities to which infants are exposed during outdoor play remains insufficiently characterized.
Methods: We characterized three playground types (kindergarten, public playground, and private garden) in both the city and its periphery, resulting in 14 sampling locations in Bielefeld, Germany. At each site, plant species were recorded. In addition, soil and sand samples (n = 27) were collected from these locations and subjected to 16S rRNA, ITS, and COI gene amplicon sequencing.
Results: The most pronounced differences were observed among soil types. Soil harbored the highest diversity of bacteria, fungi, and metazoa. Soil type also explained more than 10% of the variation in bacterial, fungal, and metazoan diversity in univariate PERMANOVA. Urbanization affected bacterial diversity, whereas for fungi and plants the effect persisted in multivariate PERMANOVA. Playground type explained up to 16% of the variation in fungi and plants, and this effect remained significant in multivariate PERMANOVA for plants. Differential abundance analysis identified six bacterial taxa, two metazoan taxa, and 24 plant species that were more or less abundant in private gardens compared to the other playground types. PERMANOVA further revealed that bacterial, fungal, and metazoan diversities were interrelated.
Conclusion: Our findings indicate that variation between biological communities is detectable even at a local level. The observed cross-kingdom interrelationships among bacteria, fungi, and metazoa suggest that these communities are not independent but are structured in a correlated manner. Together, the results highlight that both environment and land use shape the communities to which infants are exposed during outdoor play.