Fig. 1. Diversity and richness of bacteria in daycare yard soils and on the skin of daycare children.

After the trial, (A) Gammaproteobacterial and (B) total bacterial ground surface soil community was more diverse at intervention daycare yard soils compared to standard daycare yards. On the skin, the alpha diversity (Shannon index) of (C) Proteobacteria was higher among children in intervention (n = 29) and nature-oriented daycares (n = 19) compared to children in standard daycares (n = 13) after the study period. (D) Alphaproteobacterial diversity on the skin of the intervention daycare children increased during the intervention, and it was higher compared to children in standard daycares after the study period. (E) Betaproteobacterial diversity was higher among nature-oriented and (F) Gammaproteobacterial diversity higher among intervention daycare children compared to children in standard daycares after the study period. Data are displayed as means ± SE. *P < 0.05 and **P < 0.01, t tests after the intervention (A and B), Dunn’s multiple comparison post hoc tests after the intervention (C to E), and Wilcoxon signed-rank test (D).