Just under your foot is a vast world shrouded in mystery where microorganisms invisible to our unaided eyes teem with life and shape the world of humans. That life is so important that the United Nations Food and Agriculture Organization declared 2015 the International Year of Soils.
Here are four examples of how these fascinating organisms shape the ecosystems around them, often leading to benefits that can be felt at an observable scale.
▪ The hyphae – branches – of fungi coil through the soil surrounding plant roots; there, predatory fungi await their prey. These fungi release chemicals from lassolike loops to attract unsuspecting nematodes (tiny roundworms) moving through the soil in search of roots to eat. As the nematodes enter these loops, the fungi constrict the lassos, trapping the nematodes to digest them from the inside out. While the fungi have adapted this unique lifestyle as a way to find nutrients, this activity has the added benefit of protecting plant roots from the predation of nematodes.
▪ Not far from these fungi, other microorganisms are also hard at work making plant food. Nitrogen is the largest component of air and an essential building block of life – yet plants cannot use atmospheric nitrogen. They rely on a group of bacteria that can take this nitrogen gas and transform it into usable nitrogen food. This process is called nitrogen fixation and acts as a natural fertilizer promoting successful plant growth.
▪ As water infiltrates and moves through soil to the water table below, diverse microorganisms serve as a natural water filter of both chemical and living pollutants. Microorganisms consume the contaminants – thus removing them from the water supplies on which humans depend.
▪ In a constant competition for space and nutrients, microorganisms in the soil have become especially efficient at fighting and out-competing each other. The importance of these fighting mechanisms was realized when, in the 1920s, Dr. Alexander Fleming discovered that the common soil fungus Penicillium notatum contaminated and killed his cultures of disease-causing bacteria. Thanks to the follow-up experiments of Dr. Howard Florey, the antibiotic penicillin was isolated and became one of the first commercial antibiotics. Soils remain an important source of new medicines.
These examples exemplify the critical importance of soil microorganisms and our reliance upon them. However, with more microorganisms in a tablespoon of soil than there are people on Earth, there is much to be discovered about what is occurring right beneath our feet. One of the primary goals of the International Year of Soils is to promote progress in our understanding of how to foster healthy soils for our healthy future.
Julia Stevens is a postdoctoral research associate in the Genomics and Microbiology Lab at the N.C. Museum of Natural Sciences.