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A teaspoon of healthy soil can hold between 100 million and 3 billion bacteria, along with fungi, other microbes and tiny animals. Together they break down dead plants and return the nutrients that new plants need.

Biology

Science

The story behind the card

Soil life includes bacteria, fungi, archaea (single-celled microbes that form a branch of life separate from bacteria), protists (single-celled organisms such as amoebae) and animals such as nematode worms, mites and earthworms. Many fungi join plant roots in partnerships called mycorrhizae, trading water and minerals for the plant's sugars. Soil microbes touch daily life too. The smell of damp earth after rain comes partly from geosmin, a compound made by Streptomyces and other bacteria, and in 1943 streptomycin, the first antibiotic that worked against tuberculosis, was isolated from a Streptomyces bacterium living in soil. A 2023 study in the journal PNAS estimated that about 59% of all species on Earth live in soil, which makes it the richest single habitat known.

Türkçe oku
Bir çay kaşığı sağlıklı toprakta 100 milyondan 3 milyara kadar bakteri yaşayabilir; yanlarında mantarlar, başka mikroplar ve minicik hayvanlar da vardır. Bu canlılar ölü bitkileri parçalar ve yeni bitkilerin ihtiyaç duyduğu besinleri toprağa geri verir.

Toprakta bakterilerin yanı sıra mantarlar, arkeler (bakterilere benzeyen ama ayrı bir canlı kolu oluşturan tek hücreli mikroplar), amip gibi tek hücreli protistler ve nematod denen minik solucanlar, akarlar, toprak solucanları gibi hayvanlar yaşar. Pek çok mantar, bitki kökleriyle mikoriza denen bir ortaklık kurar: Bitkiye su ve mineral taşır, karşılığında ondan şeker alır. Toprak mikropları gündelik hayatımıza da dokunur. Yağmurdan sonra yükselen ıslak toprak kokusu kısmen, Streptomyces ve başka bakterilerin ürettiği geosmin adlı bileşikten gelir. Vereme karşı etkili ilk antibiyotik olan streptomisin de 1943'te topraktaki bir Streptomyces bakterisinden elde edildi. PNAS dergisinde 2023'te yayımlanan bir çalışmaya göre Dünya'daki türlerin yaklaşık %59'u toprakta yaşıyor; bu da toprağı bilinen en zengin yaşam alanı yapar.

Sources and further reading

Background reading: Soil biology
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