Plant microbiomes are surprisingly complex due to competition as well as cooperative relationships, such as interdependence, but the relative contributions of competition vs. cooperation remain unclear. To learn more, researchers recently predicted the functions and metabolite networks of 193 types of bacteria from the roots of the model plant Arabidopsis. They found that different taxonomic groups of bacteria produced distinct sets of metabolites, and simulations with random synthetic combinations of bacteria suggested that increasingly diverse combinations produced more metabolites. However, most combinations had an optimal diversity level, beyond which the metabolic functions remained redundant. In fact, relatively small combinations reflected the metabolic capacity of the whole microbe community. Most strains could produce almost all of a set of 30 metabolites, including amino acids, vitamins, and plant hormones. The production of these metabolites depended on nutrient availability and was facilitated by root-like nutrient conditions. Furthermore, numerous sets of interdependent strains could produce the metabolites under severe nutrient limitations. Although experimental work is needed, the results suggest the existence of metabolic cooperation among root microbes that helps meet important functional needs in different nutrient conditions.