Research unearths the science behind the smell of spring
You may not have heard of geosmin but it is highly likely that you’d recognise its smell.
Geosmin is the soil-based compound that gives the evocative, earthy smell so characteristic of spring. It’s best appreciated after recent rainfall or while digging. The human nose is so sensitive to the compound that it is detectable at one hundred parts per trillion.
But why does it exist? New research by scientists in Sweden and the UK has helped to explain why.
The secret, according to the study published in Nature Microbiology for which I am one of the co-authors, lies in an ancestral mutual relationship between the soil bacteria Streptomyces and primitive, six-legged creatures called springtails (Collembola).
Streptomyces are globally significant bacteria that produce a range of organic compounds, including chemical weapons to fight off enemies in the soil. These have been exploited for human use as some world’s most effective antibiotics.
They also produce geosmin and a range of other volatile organic compounds. While Streptomyces species vary drastically in the types of molecules they produce as antibiotics, they all, without exception, produce geosmin.
The fact that they all make geosmin suggested that it confers a selective advantage on the bacteria.
Professor Mark Buttner of the John Innes Centre
