Publication
Naturally-diverse airborne environmental microbial exposures modulate the gut microbiome and may provide anxiolytic benefits in mice
Publisher:
Elsevier BV
Date:
2020
DOI:
10.1016/J.SCITOTENV.2019.134684
Abstract: Growing epidemiological evidence links natural green space exposure with a range of health benefits, including for mental health. Conversely, greater urbanisation associates with increased risk of mental health disorders. Microbiomes are proposed as an important but understudied link that may help explain many green space-human health associations. However, there remains a lack of controlled experimental evidence testing possible beneficial effects from passive exposure to natural bio ersity via airborne microbiota. Previous mouse model studies have used unrealistic environmental microbial exposures-including excessive soil and organic matter contact, feed supplements and injections-to demonstrate host microbiota, immune biomarker, and behavioural changes. Here, in a randomised controlled experiment, we demonstrate that realistic exposures to trace-level dust from a high bio ersity soil can change mouse gut microbiota, in comparison to dust from low bio ersity soil or no soil (control) (n = 54 total mice, comprising 3 treatments × 18 mice, with 9 females + 9 males per group). Furthermore, we found a nominal soil-derived anaerobic spore-forming butyrate-producer, Kineothrix alysoides, was supplemented to a greater extent in the gut microbiomes of high bio ersity treatment mice. Also, increasing relative abundance of this rare organism correlated with reduced anxiety-like behaviour in the most anxious mice. Our results point to an intriguing new hypothesis: that bio erse soils may represent an important supplementary source of butyrate-producing bacteria capable of resupplying the mammalian gut microbiome, with potential for gut health and mental health benefits. Our findings have potential to inform cost-effective population health interventions through microbiome-conscious green space design and, ultimately, the mainstreaming of bio ersity into health care.