Article Figures & Data
Figures
- FIG 1
Hong Kong MTR network map and information, including ridership information and connectedness of lines included in this study. (A) Schematic representation of MTR lines sampled in this study. The network map is not drawn to scale. Lines are color coded, and corresponding outdoor locations are indicated with the same color as the lines; the station is shaded yellow. (B) MTR line and ridership information are based on 2010 figures (http://gia.info.gov.hk/general/201106/08/P201106080126_0126_79963.pdf). (C) Pairwise comparisons between the lines are represented as a matrix. To systematically represent connectedness between lines, a system was devised considering the number of interchange stations (stations with oval shapes) between lines and the shortest distance between two lines if no interchange station is shared. Matrix of line-to-line connectedness for the line pair with interchange stations are represented as 1/x, where x is the number of shared interchange stations. For example, the Island (blue) and Tsuen Wan (red) Lines share two stations; hence, their connectedness is 1/2. The interchange stations allow one to go from one line to another in both directions. For lines with no sharing station, the distance is represented by the shortest unit distance separating the two lines, where one step is traveling from one station to the next or the change of a line. For example, as illustrated, from Kwun Tong Line (green) to Island Line (blue), a minimum of three steps are required, with a change from the Kwun Tong to the Tseung Kwan O (purple) Line (step 1), followed by traveling one station (step 2), and then changing from the Tseung Kwan O to the Island Line (step 3). The dotted line adjacent to the station Tsim Sha Tsui East can be treated as an interchange station for the study.
- FIG 2
Major phyla detected in MTR and outdoor samples. Each group represents the collection of samples within a given sample type, either a particular line or an outdoor location. The plot is arranged by similarities in proportions of phyla between samples. The corresponding outdoor samples are placed to the right of a set of train line samples. Taxonomic assignment was performed using the open-reference method, based on 97% sequence identity cutoff against a filtered Greengenes database to include only sequences with taxonomic information down to the genus level. The top five phyla present across the data set are indicated. Minor/unclassified includes sequences assigned to the remaining phyla according to the Greengenes database and de novo sequences with no Greengenes sequences sharing ≥97% identity.
- FIG 3
Relationship between MTR line community composition and corresponding outdoor locations. A Bayesian source-tracking approach (37) was used to represent the mean proportions of contributions of each outdoor-location bacterial community on each line. An overlap between line (sink) and outdoor (source) microbiomes is represented by ≥97% identity between sequences of the two sample environments. Sequences in which SourceTracker could not confidently assign a source environment are placed in the unknown category. The outdoor location corresponding to a specific line is indicated with a black bracket for each bar. While Causeway Bay was chosen as the corresponding location for the Island Line, Admiralty (dotted bracket) is also along the Island Line; hence, it also should be considered a source for this line.
- FIG 4
PCoA plot of phylogenetic dissimilarity between samples of different geographical regions. Comparison was performed between Hong Kong samples collected in this study and previous works investigating urban environments in the United States (5, 36). The plot was constructed based on abundance-weighted UniFrac phylogenetic distance. GOF represents the goodness of fit, an indication of the representation of the PCoA plot to the UniFrac distance data. PCoA dimensions 1 and 2 show 30% and 33% of the variances, respectively.
Tables
- TABLE 1
Comparison of β-diversity between sample types according to unweighted and weighted UniFrac distances
Comparison by structure and time Global R (unweighted) P valuea Global R (weighted) P valuea Spatial/architectural MTR vs outdoor −0.023 NS 0.046 NS Outdoor vs outdoor 0.161 0.021 −0.003 NS Line vs line 0.207 0.001 0.082 0.001 Underground vs above ground 0.232 0.001 0.064 0.004 Temporal a.m. vs p.m. 0.062 0.001 0.029 0.03 Peak vs nonpeak −0.005 NS 0.109 0.001 ↵a NS, not significant (P > 0.05). Boldfaced values indicate statistical significance.
Supplemental material
Files in this Data Supplement:
- Supplemental file 1 -
Architectural design of MTR lines (Fig. S1); rarefaction curves for α-diversity metrics (Fig. S2); box plots of α-diversity comparison between sample types (Fig. S3); comparison of environmental conditions between sample types (Fig. S4); correlation between environmental conditions and α-diversity on the MTR (Fig. S5); characteristics, diversities, and sampling coverage for samples included in the study (Table S1); relative abundance in percentages of top 10 genera across total dataset and by sample types (Table S2); SIMPER analysis of abundances in percentages of skin-associated OTUs across different sample types (Table S3); average temperature, relative humidity, and CO2 measurements for sample types (Table S4).
PDF, 1.6M
- Supplemental file 1 -
