Urban Transit System Microbial Communities Differ by Surface Type and Interaction with Humans and the Environment.
Public transit systems are ideal for studying the urban microbiome and interindividual community transfer. In this study, we used 16S amplicon and shotgun metagenomic sequencing to profile microbial communities on multiple transit surfaces across train lines and stations in the Boston metropolitan transit system. The greatest determinant of microbial community structure was the transit surface type. In contrast, little variation was observed between geographically distinct train lines and stations serving different demographics. All surfaces were dominated by human skin and oral commensals such asPropionibacterium,Corynebacterium,Staphylococcus, andStreptococcus. The detected taxa not associated with humans included generalists from alphaproteobacteria, which were especially abundant on outdoor touchscreens. Shotgun metagenomics further identified viral and eukaryotic microbes, includingPropionibacteriumphage andMalassezia globosa. Functional profiling showed thatPropionibacterium acnespathways such as propionate production and porphyrin synthesis were enriched on train holding surfaces (holds), while electron transport chain components for aerobic respiration were enriched on touchscreens and seats. Lastly, the transit environment was not found to be a reservoir of antimicrobial resistance and virulence genes. Our results suggest that microbial communities on transit surfaces are maintained from a metapopulation of human skin commensals and environmental generalists, with enrichments corresponding to local interactions with the human body and environmental exposures.IMPORTANCEMass transit environments, specifically, urban subways, are distinct microbial environments with high occupant densities, diversities, and turnovers, and they are thus especially relevant to public health. Despite this, only three culture-independent subway studies have been performed, all since 2013 and all with widely differing designs and conclusions. In this study, we profiled the Boston subway system, which provides 238 million trips per year overseen by the Massachusetts Bay Transportation Authority (MBTA). This yielded the first high-precision microbial survey of a variety of surfaces, ridership environments, and microbiological functions (including tests for potential pathogenicity) in a mass transit environment. Characterizing microbial profiles for multiple transit systems will become increasingly important for biosurveillance of antibiotic resistance genes or pathogens, which can be early indicators for outbreak or sanitation events. Understanding how human contact, materials, and the environment affect microbial profiles may eventually allow us to rationally design public spaces to sustain our health in the presence of microbial reservoirs.Author Video: An author video summary of this article is available.
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA; Broad Institute, Cambridge, Massachusetts, USA.
Tiffany
T
Hsu
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
Regina
R
Joice
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
Jose
J
Vallarino
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
Galeb
G
Abu-Ali
University of Oregon, Eugene, Oregon, USA.
Erica M
EM
Hartmann
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
Afrah
A
Shafquat
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
Casey
C
DuLong
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
Catherine
C
Baranowski
Broad Institute, Cambridge, Massachusetts, USA.
Dirk
D
Gevers
University of Oregon, Eugene, Oregon, USA.
Jessica L
JL
Green
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA; Broad Institute, Cambridge, Massachusetts, USA.
Xochitl C
0000-0002-6264-6961
XC
Morgan
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
John D
JD
Spengler
Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA; Broad Institute, Cambridge, Massachusetts, USA.
Curtis
0000-0002-1110-0096
C
Huttenhower
built environment; microbiome; subway; transit