Microbial communities living on and around plants influence plant growth and health in positive or negative ways, but the factors that determine these outcomes are not well understood. Gaining insight into how these microbial communities function is essential for improving crop performance, reducing losses to disease, and supporting food security. This project will investigate how the composition and characteristics of root-associated microbial communities shape plant development and health. By combining biology, engineering, and machine learning, the team will identify bacterial strains that, when assembled into communities, promote plant growth and help protect against disease. These findings will support the development of beneficial microbial products that enhance crop performance and reduce agricultural inputs. The project will also train undergraduate and graduate students, provide summer research opportunities for high school students, and support K–12 science education through a training workshop for local teachers on plant microbiomes and related science and engineering topics. Although plant microbiomes play a major role in influencing plant outcomes, we have a poor understanding of the causal links between the functional properties of microbiomes and plant host phenotypes. This project will use a well-characterized collection of plant-associated bacterial strains to construct a variety of synthetic communities and study how specific combinations affect plant gro