Environmental microbiota transfer from forest soil into urban homes: a proof-of-principle study

Area of Science:

• Environmental microbiology
• Human health
• Urban ecology

Background:

• Urban lifestyles reduce exposure to environmental microbes, increasing risks of inflammatory diseases, asthma, and allergies.
• Modifying indoor microbial exposures may offer a preventative strategy for these conditions.

Purpose of the Study:

• To test the feasibility of transferring environmental microbiota into urban homes.
• To quantify the spatiotemporal impact of these transfers on the built environment microbiota.

Main Methods:

• Six Finnish homes were monitored for 20 weeks, collecting settled dust from infant (IBZs) and adult breathing zones (ABZs) and floor dust.
• Microbiota analysis involved qPCR and amplicon sequencing of bacterial, archaeal, and fungal DNA.
• Microbiota transfers were conducted by seeding forest soil onto entryway rugs.

Main Results:

• Significant increases in forest soil bacteria were observed in house dust post-intervention.
• The effect varied based on building, spatiotemporal, and occupant dynamics, being strongest in homes with low microbial influx.
• Increased bacterial diversity and an asthma-protective microbiota index were noted in airborne dust near rugs, alongside a decrease in human-sourced bacteria.

Conclusions:

• A simple soil-to-rug intervention can modify bacterial microbiota in indoor airborne particulate matter.
• The impact of introduced soil microbes was most pronounced near the source, relevant for infant exposure.
• Further research is needed to determine optimal dosage and composition for health benefits.