"Soils Support Health" is the August theme for the Year of Soils, sponsored by the United Nations Food and Agriculture Organization and supported by the Soil Science Society of America.
It's a fitting theme, according to Chuck Rice, a soil microbiologist and distinguished professor of agronomy at Kansas State University, who says more than a billion different bacteria, fungi, archaea and protists – all of which have an important job that impacts human, animal and plant health – live in a single teaspoon of soil.
What's more, scientists only know about 1% of these bacteria.
"It's fascinating, at least for microbiologists, because some would argue soil has the most diverse ecosystem. The most unknown living organisms are in the soil," Rice said.
While many people understand how important soil is for plants, the soil also cleans water. In addition, about 90% of antibiotics we use currently come from microbes. Other drugs, including anti-cancer and immunosuppressant drugs, have been discovered in soil as well.
"If you realize that we only know 1% of those microbes in the soil," Rice said, "what are the other 99 percent doing for us or have the potential to do for us?"
In addition to supplying humans with micronutrients in foods for growth and development, and drugs to ward off diseases, soil microbes are the key components for health in all features of the planet—such as water, air and other aspects of the environment.
History of efforts in medicine
Rice said perhaps the two most famous instances of using soils to create disease-fighting drugs are Alexander Fleming's discovery of penicillin and Selman Waksman's discovery of several antibiotics, including streptomycin—the first effective antibiotic to treat tuberculosis.
These drugs, discovered in 1928 and 1943 respectively, were discovered using cultures of soil microbes.
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Traditionally, these drugs have been discovered on agar plates. The scientists examined these plates to find where disease cultures were growing and where they were not. The microbes fought culture growth in the bare areas; therefore, they could be isolated, replicated and used in medicines.
"We have concerns about the over-use of antibiotics and antibiotic resistance," Rice said. "By digging down into the soil, we can now find new antibiotics that will help overcome the resistance that has occurred naturally from use in humans and animals."
Most of the "unknowns," however, don't grow on agar plates. Instead, a technique called metagenomics is being used to allow scientists to extract the DNA of microbes directly from the soil. A new class of antibiotics was discovered in early 2015 using this new method.
"It's not well appreciated that the microbes that live in soil live in a harsh environment," Rice explained. "They're used to that, but when we try to put them in a perfect environment, they don't grow easily."
Continued need for soil health
Soil is an extremely valuable resource, Rice said, and if we lose the healthiness of the soil, we lose potential organisms that could help us directly through disease management and through the foods we consume.
Nutrients, particularly micronutrients like zinc, are critical for human physical and mental development, he said. Microbes live on plant roots and supply the plant such nutrients. So, low zinc levels in depleted soils can affect zinc levels in plants and the development of children who consume them.
Likewise, soil health helps protect the environment. Microbes in soil help sequester carbon, Rice said. They take carbon out of the atmosphere through plants and help store it in the soil, which helps moderate and protect the climate.
Researchers are studying how toxicity in the soil that comes from lead and arsenic, as examples, can be combated with microbes that bind to those elements and prevent water contamination. Rice said soils are commonly used to in septic tanks and help purify wastewater.
"We count on the microbes to clean up that water, so as it leeches through to groundwater or runs off the surface, that water is drinkable," he said. "With water shortage, we're looking at ways to use recycled water for other uses, and it's the microbes that help clean it up."
See Rice's discussion about soils and health on the K-State Extension youtube channel.