Urban transportation systems have been studied as vectors for the transmission of infectious disease, but their role in moving harmless microbes among hosts is largely unknown. This grant funds a project by Curtis Huttenhower, associate professor of computational biology at Harvard’s T.H. Chan School of Public Health and associate member of the Broad Institute, to determine the metabolic activity of host- and environmentally derived microbes in the public transportation microbiome and reconstruct associated biochemical pathways. Huttenhower’s study will determine the degree to which transit-associated microbial communities are functionally active as well as the basic microbial biochemical processes by which they persist in situ and (re-) transmit to and from human hosts. The team plans to share functional data and metadata through open access repositories. Manuscripts will be made open access whenever possible, and all software will be made freely available open source commensurate with the lab's existing work. The team expects to publish at least two papers and present the work at two conferences.