Root nodules on tepary bean roots (IMAGE) American Society of Agronomy Caption Tepary roots have been dug up to examine them for the presence of nodules. Nodules are the light-colored, spherical areas on the roots. They were formed by beneficial soil microbes that "set up shop" in the roots to get some sugars from the host-plant while they fix atmospheric nitrogen, which plants need to grow. Credit Tomilee Turner Usage Restrictions For use with this story only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.