What makes dirt smell

That's probably because these bacteria must battle for resources with so many other microbes in the dirt jungle. Any given Streptomyces can produce dozens of unusual chemicals, but any particular chemical is usually made by only a few.

Yet even though scientists knew where that smell was coming from, they didn't know the answer to another basic question: why make it? A team of British, Hungarian, and Swedish scientists investigated this question recently, publishing their findings this month in Nature Microbiology.

The natural history of these bacteria contains a clue. Streptomyces, amazingly for bacteria, behave like fungi. Fungi grow as a mass of branched filaments called mycelium that often sprouts individual reproductive cells called spores. In spite of the bacterial reputation for making tiny individual cells, Streptomyces does this too. But because they live immersed in dirt, dispersing those spores is difficult.

Wind and water are unpredictable and unlikely to get you very far. The remaining options comprise miscellaneous creepy crawlies. So the scientists put two and two together: is geosmin the bacterial equivalent of the smell of ripe fruit?

To answer that question, they built tiny traps baited with Streptomyces bacteria, placed them in the field and waited. What showed up in those traps relative to unbaited control traps were springtails. Springtails are omnivores that feed on a wide array of microbes and plant parts. They are also abundant in the top layer of soil where Streptomyces live. These adorable little creatures are so named because they often have a forked butt flipper called a furcula that launches them skyward in emergencies.

The scientists investigated whether springtails can smell dirt smells by checking for an electrical response in their antennae to the relevant odors. Geosmin and 2-MIB both elicited such responses. Would Streptomyces spores stick to springtails? The bodies of springtails are covered in extremely hydrophobic wax, meaning they repel water and most bacteria.

Meganathan Smell of soil is due to the smell of two small molecules produced by small organisms. Gerber, N. CRC Crit. Bentley, R. FEBS Lett. Jiang, J; He, X.

Spiteller, D. Phytochemistry 61, — Wang, C. Simons, P. The Guardian, March ,6, Can you describe the smell of soil in a forest, freshly tilled field, or in a swamp? Have you ever wondered if fresh tilled soil has always had the same sweet aroma? The smell will be different depending on where the soil is found. Healthy, productive soils should smell fresh, clean and pleasant or have little odor at all. If the soil smells like ammonia or has a rotten odor that is a good indication there is poor drainage or lack of oxygen in the soil.