Residential green space can shape the indoor microbial environment

Abstract Background The influence of outdoor green space on microbial communities indoors has scarcely been investigated. Here, we study the associations between nearby residential green space and residential indoor microbiota. Methods We collected settled dust from 176 living rooms of participants of the ENVIRONAGE birth cohort. We performed 16S and ITS amplicon sequencing, and quantitative PCR measurements of total bacterial and fungal loads to calculate bacterial and fungal diversity measures (Chao1 richness, Shannon and Simpson diversity indices) and relative abundance of individual taxa. Green spaces were estimated within 50m and 100m buffers around the residential address. We defined total residential green space using high-resolution land-cover data, further stratified in low-growing (height 3m). We used land-use data to calculate the residential nature. We ran linear regression models, adjusting for confounders and other potential determinants. Results are expressed as units change for an interquartile range (IQR) increase in residential green space and their 95% confidence intervals (CI). Results After adjustment, we observed statistically significant associations between the indoor microbial diversity indices and nearby residential green space. For bacteria, the Shannon index was directly associated with residential nature (e.g. 0.08 units increase (CI:0.02,0.13) per IQR increase in nature within a 50m buffer). Fungal diversity was directly associated with high-growing residential green and inversely with low-growing green. For example, an IQR increase in high-growing green within a 50m buffer was associated with increases in 0.14 (CI:0.01,0.27) and 0.02 (CI:0.008,0.04) units in the Shannon and Simpson indices, respectively. Conclusions Nearby green space determines the diversity of indoor environment microbiota, and the type of green differently impacts bacterial and fungal diversity. Further research is needed to investigate in more detail possible microbial taxa compositions underlying the observed changes in indoor microbiota diversity and to explore their contribution to beneficial health effects associated with green space exposure.