Plants represent a cost-effective way to clean up contaminated sites in a process called phytoremediation. The byproducts of the mining process, called mine tailings, can be decontaminated this way, but contaminated sites are often deficient in important nutrients, like nitrogen (N). These deficiencies hinder plant growth and impair the phytoremediation process. But some microbes, called diazotrophs, can help the pioneering plants grow by converting, or fixing, atmospheric N into plant-usable forms. A recent study looked at endophytes, which are internal microbial symbionts of plants, and their impact on pioneering phytoremediation plants. The researchers first identified several crucial endophyte groups for Chinese silvergrass (Miscanthus sinensis) grown in mine tailings. They then found that members of Rhizobium and Pseudomonas in particular could help pioneer plants grow by fixing N. First, experiments tracing labeled N and genomic analysis both suggested that these bacterial groups were diazotrophic. Second, inoculating another pioneer plant, Bidens pilosa, with a species from each genus successfully increased N fixing activity and plant growth. These results revealed that it is specialized keystone bacterial groups that fix N in these systems and that these bacteria could potentially be used as microbial agents to improve the efficacy of mine tailing phytoremediation.