Behind the Fresh Smell of the Land After the Rain

That evening when I was enjoying a cup of coffee with my family on the back porch of the house. I suddenly missed something. Rain. Yes, my city hasn’t been raining for a long time.

Actually, it’s not just the rain that I miss. But also the fresh and distinctive smell when it starts to wet the ground. The momentum of copying in the afternoon feels perfect if coupled with the smell of the smell.

But later I learned that the fresh and unpretentious aroma was not because the soil was soaked by rainwater. Then, what is the cause of the smell that is often many people?

Recent research shows that the scent is a ‘chemical compound’ that bacteria use to attract tiny arthropods. For more than 400 million years.

When was this research discovered?

Indeed, since the 1960s scientists have known about the ‘chemical compounds. Behind the creation of aromas. from the ground when it was only wet with rain called geosmin. Only researchers have now discovered that might be an explanation of what the odor’s purpose was actually created.

It turned out that not only me (humans) were sensitive to this geosmin. But also many animals and other insects including flies, camels, and others.

The bacteria responsible for this odor are in the genus Streptomyces. Which is famous for producing unique chemical byproducts. Which form the basis of many compounds in antibiotics, antifungal, and anticancer drugs.

But each of these unique compounds is only made by a fraction of the more than 500 species. Known in the genus. However, 120 of the 122 species studied by researchers have genes to produce geosmin.

The facts

Show that bacteria make geosmin to give them certain benefits because otherwise, they might make it.

The geosmin that accompanies these bacterial spores, present in large quantities in soils throughout the world. Experts suspect it could be a signal to some animals or insects that might help spread the spores.

To see what creatures are attracted to the scent. The research team created a network of sticky traps in the Alnarp forest, Sweden. Some were given Streptomyces bait and other traps were given a kind of soy flour.

Infield experiments and in this laboratory. The pungent smell of geosmin, and another compound called 2-methylisoborneol (2-MIB). Which was released by the Streptomyces colony turned out to attract small six-legged arthropods or called springtails came in droves.

What about research?

The researchers even inserted electrodes into springtails’ antennas. Because the ‘antenna’ moves every time the chemical smells. The researchers conclude that springtails adjust the antenna specifically towards geosmin and 2-MIB.

The results showed that these organisms evolved together to form a symbiotic relationship. Streptomyces uses geosmin to ‘ring the dining bell’ for hungry springtails. Which eat bacteria, and in return these six-legged arthropods spread bacterial spores far and wide.

Springtails spread the spores they have eaten through their droppings while what is sticking to their bodies is only peeling.

So it’s like a bird analog that eats the fruit of a plant. They get food but they also distribute seeds, which are beneficial to plants.

There is also evidence that the bacteria genus Streptomyces apparently prefers springtail to convey their spores. Why? Because of the many compounds produced by Streptomyces, many are deadly to fungi, insects, and nematodes.

Another case with Springtails. Arthropods were separated from the insect family about half a billion years ago and have enzymes. That is able to deal with many chemical compounds Streptomyces.

So, these small primitive animals play an important role in completing the life cycle of Streptomyces. One of the most important sources of antibiotics known to science.

The researchers write that this symbiotic relationship is likely hundreds of millions of years old. So, the next time you smell the earth after the rain, bring your imagination to the time of the dinosaurs. Because the same smell actually has been smelled since ancient times.

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