A unique but flawless fragrance heralds the arrival of spring. While it has a slightly country-like quality, there is another element that makes one think of rainy days or garden afternoons.
The crux? The soil-based substance called geosmin is the source of such surprising olfactory experiences. In fact, this chemical compound is so well adapted to our nose that humans can distinguish it better than sharks can distinguish blood.
Researchers from the Swedish University of Agricultural Sciences, the John Innes Center and Lund University have discovered for the first time the reason for the persistence of this distinctive odor: a symbiotic relationship between the bowtail, a six-legged worm, and streptomyces, a bacteria commonly found in soil.
In their article published in the 2020 issue of the journal Nature Microbiology, the scientists state that “in field experiments, bowtails were influenced by the odors emitted by Streptomyces colonies.”
Streptomyces, on the other hand, creates organic molecules that are used in everything from antibiotics to chemical weapons. It also forms geosmin and other volatile organic compounds (VOCs) that can be easily converted to steam or gas.
According to Mark Buttner, one of the study's authors, "[Streptomyces'] producing geosmin suggests that this gives bacteria a selective advantage, otherwise they wouldn't have done it." We guessed they were communicating with something, and an animal or insect that could help spread Streptomyces spores appears to be the most likely candidate.
To test this theory, researchers in Sweden set up two sets of traps, one baited with Streptomyces and the other baited with control materials. Bowtails were attracted to Streptomyces bait at first glance, but the researchers wanted to investigate further.
The bowtails were then placed individually inside a Y-tube to prevent herd behavior to see if they followed the geosmin scent. In a third set of experiments, the team placed small electrodes on the bowtails' antennae and watched how they responded to various chemicals.
The Role of Springtails
The lab discovered the same thing each time: geosmin and another substance called 2-methylisoborneol, produced by Streptomyces, attract bowtails.
- Although difficult to pinpoint exactly, geosmin, an organic molecule often found in soil, is a definitive source for spring's distinctive scent.
- Scientists in England and Sweden have found the reason why the scent of spring lasts through the ages, thanks to the symbiotic bond between the soil bacterium Streptomyces and the six-legged creatures known as bowtails.
- The researchers' findings were published in the journal Nature Microbiology in April 2020.
Although Streptomyces often kills fruit flies and nematodes, it turns out that geosmin and 2-MIB act as chemical signals that direct springtails toward bacteria so they can use it as a food source. Springtails, which diverged from insects about 500 million years ago, contain several enzymes that detoxify antibiotics produced by Streptomyces.
Springtails assist Streptomyces in exchange for a food supply by dispersing their spores, which can adhere to their bodies and eventually fall off or spread through feces.
According to Buttner, this is “like birds eating the fruit of plants.” “They get food, but they also share seeds, which is good for plants.” Streptomyces was once assumed to have been dispersed by wind and water, according to scientists.
This is an example of 450 million years of symbiosis that has stood the test of time. So, when worms dig in the ground after the next spring rain and your nostrils detect that strong earthy aroma, you can thank springtails and Streptomyces for continuing their old dance.
Günceleme: 26/03/2023 16:55