Smart Farming: How Microbes Help Our Crops Test
The microbial communities on and around plants are critical to manufacturing the nutrients that plants need in order to grow. Certain bacteria convert atmospheric nitrogen into ammonia, a form that is readily usable by plants and animals. Other soil microbes recycle nutrients from decaying plants and animals, while still others convert elements, such as iron and manganese, to forms that can be used for plant nutrition. However, it takes a community to perform these critical biotransformations. For example, no one microbe is capable of converting ammonia to nitrate, yet teams of microbes do this very efficiently.
Keeping Crops Healthy
One of the most valuable but least understood mysteries of farming is the "suppressive soil" phenomenon. In suppressive soils, plants stay healthy even when disease-causing organisms are present in high densities. If this soil is sterilized, killing helpful and harmful microbes alike, plants can become sick and die once the pathogens find their way back into the soil. 
Scientists speculate that microbes living in the suppressive soil actually protect plants from diseases—and if these microbes disappear, plants are far more susceptible to infection. Despite decades of research, scientists have only been able to pinpoint the microbes responsible for suppressing disease in a few locations. Scientists believe that a complex microbial community is responsible for suppressing disease, because no single microbial species can do it alone. The activities of suppressive soil communities are enormously beneficial to agriculture.
While scientists have been able to glimpse the complex microbial communities that help keep crops healthy and productive, much about those communities remains mysterious. Metagenomics offers a unique opportunity to explore how microbial communities interact with crops and may eventually lead to ways to harness the power of soil microbial communities to produce healthier and more robust crops.
The information on this Web page was derived from the National Research Council report The New Science of Metagenomics: Revealing the Secrets of Our Microbial Planet (2007) and the 20-page educational booklet derived from that report, Understanding Our Microbial Planet: The New Science of Metagenomics.
PHOTO CREDITS: (from top) Farmer image courtesy USDA; Metagenomics at work photo courtesy Jo Handelsman, University of Wisconsin-Madison; Tractor photo courtesy Jim Tiedje, Michigan State University.
Support for this web publication was provided by the Presidents' Circle Communication Initiative of the National Academies.
