Rhizobia (IMAGE) University of Massachusetts Amherst Caption UMass Amherst researchers identified a key molecule in nitrogen-fixing bacteria, here stained green, that take residence in host cells. Host nuceli are stained red. Credit UMass Amherst/Chris Waters Usage Restrictions None 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.