Urban soil Gammaproteobacteria diversity, shaped by biodiverse land use, predicts a lower risk of developing allergy in children

Source abstract

Urbanisation has led to reduced exposure to environmental microbiota, potentially with negative consequences for human health. The biodiversity hypothesis suggests that contact with diverse environmental microorganisms, particularly soil-dwelling Gammaproteobacteria , is associated with immune regulation and may reduce allergy risk. We investigated this hypothesis in Tartu, an Estonian city (ca. 100,000 inhabitants) in Northern Europe, by integrating citywide ecological data with clinical information. Using a cohort of 148 children, we assessed the relationship between atopy (atopic sensitisation, a tendency to develop allergic diseases) and proximity to urban green spaces with high Gammaproteobacteria diversity. This spatial linkage was possible through an intensive citywide soil microbial eDNA survey covering 743 green spaces. We found that children living closer to green spaces characterised by high soil Gammaproteobacteria diversity had a significantly lower probability of atopy than those living farther away. Additionally, atopy was positively associated with the wealth of the neighbourhood and negatively associated with the abundance of urban grasslands. The diversity of Gammaproteobacteria was positively associated with plant diversity and the nearby presence of urban woodlands and negatively associated with soil fertility (potassium concentration). Notably, children's daycare yards exhibited higher Gammaproteobacteria diversity than public green areas. These findings support the biodiversity hypothesis in an urban context and highlight the importance of microbial exposure in early life, offering insights for integrating microbial biodiversity into urban design and public health policy. In particular, urban planning strategies that promote plant diversity, preserve urban grasslands and woodlands, and support biodiverse daycare environments may enhance public health.