Gilbert's research is focused on the ecology, evolution, and metabolic dynamics of microbial ecosystems from myriad environments including built environments, oceans, rivers, soils, air, plants, animals, and humans. His primary interest is in using omics technologies (metagenomics, metatranscriptomics, metabolomics) to capture longitudinal dynamics in microbial ecosystems and then model how these interactions relate the environmental variables, be those variables disease onset and immunology in humans or chemical transformations in plants and soils. Gilbert is developing unifying principles which govern how microbial communities assemble. He founded the Earth Microbiome Project, and co-founded the American Gut Project, and is the editor-in-chief of the journal mSystems.