Abstract

Although studies have shown that urban environments and mass-transit systems have geospa-tially distinct metagenomes, no study has ever systematically studied these dense, human/microbial ecosystems around the world. To address this gap in knowledge, we created a global metagenomic and antimicrobial resistance (AMR) atlas of urban mass transit systems from 58 cities, spanning 3,741 samples and 4,424 taxonomically-defined microorganisms collected for three years. The map provides annotated, geospatial data about microbial strains, functional genetics, antimicrobial resistance, and novel genetic elements, including 10,928 novel predicted viral species. Urban microbiomes often resemble human commensal microbiomes from the skin and airways but contain a consistent “core” of 61 species which are predominantly not human commensal species. These data also show that AMR density across cities varies by several orders of magnitude with many AMRs present on plasmids with cosmopolitan distributions. Conversely, samples may be accurately (91.4%) classified to their city-of-origin using a linear support vector machine over taxa. Together, these results constitute a high-resolution global metagenomic atlas, which enables the discovery of new genetic components of the built human environment, forensic application, and an essential first draft of the global AMR burden of the world’s cities.