Bacterial synergies amplify nitrogenase activity in diverse systems.

Here, we report the isolation of robust N-fixing endophytes from plants growing at nutrient-limited sites. A diazotrophic strain from Hawaiian lava field plants co-isolated with a community of non-diazotrophic strains, one of which amplified nitrogenase activity of the diazotroph. A similar microbial partnership was also discovered in roots of Populus trees on a nutrient-limited gravel bar. The synergistic strains also increased the nitrogenase activity of unrelated diazotrophic endophytes, pointing to an important role of these microbial interactions. In this study, we also identified related strains that did not have the synergistic effect, suggesting that specific microbial interactions are at play.