Evolving microbes - 3 (IMAGE) University of Toronto Caption Specimens of the clover-like Medicago truncatula plant were each given an initial mixture of two strains of the nitrogen-fixing bacteria Ensifer meliloti to learn what happens to microbes when paired with the same host across multiple generations. Credit Bill Cole 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.