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. 2017 Apr 6;12(4):e0175527.
doi: 10.1371/journal.pone.0175527. eCollection 2017.

Filthy Lucre: A Metagenomic Pilot Study of Microbes Found on Circulating Currency in New York City

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Free PMC article

Filthy Lucre: A Metagenomic Pilot Study of Microbes Found on Circulating Currency in New York City

Julia M Maritz et al. PLoS One. .
Free PMC article

Abstract

Background: Paper currency by its very nature is frequently transferred from one person to another and represents an important medium for human contact with-and potential exchange of-microbes. In this pilot study, we swabbed circulating $1 bills obtained from a New York City bank in February (Winter) and June (Summer) 2013 and used shotgun metagenomic sequencing to profile the communities found on their surface. Using basic culture conditions, we also tested whether viable microbes could be recovered from bills.

Results: Shotgun metagenomics identified eukaryotes as the most abundant sequences on money, followed by bacteria, viruses and archaea. Eukaryotic assemblages were dominated by human, other metazoan and fungal taxa. The currency investigated harbored a diverse microbial population that was dominated by human skin and oral commensals, including Propionibacterium acnes, Staphylococcus epidermidis and Micrococcus luteus. Other taxa detected not associated with humans included Lactococcus lactis and Streptococcus thermophilus, microbes typically associated with dairy production and fermentation. Culturing results indicated that viable microbes can be isolated from paper currency.

Conclusions: We conducted the first metagenomic characterization of the surface of paper money in the United States, establishing a baseline for microbes found on $1 bills circulating in New York City. Our results suggest that money amalgamates DNA from sources inhabiting the human microbiome, food, and other environmental inputs, some of which can be recovered as viable organisms. These monetary communities may be maintained through contact with human skin, and DNA obtained from money may provide a record of human behavior and health. Understanding these microbial profiles is especially relevant to public health as money could potentially mediate interpersonal transfer of microbes.

Conflict of interest statement

Competing Interests: RJP is an employee of IBM Almaden Research Center. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1
Fig 1. Flowchart describing the experimental plan and workflow for sample collection, sequencing and metagenomic data analysis.
Fig 2
Fig 2. Comparison of organisms identified in the Winter 2013 data by direct annotation of unassembled reads and de novo metagenomic assembly analysis methods.
(A) Proportion of human matches identified by Bowtie2 (unassembled reads) and megaBLAST-LCA (assembled reads). (B) Proportional distribution of non-human megaBLAST-LCA results. Low quality matches are defined as those filtered out prior to LCA analysis (see Materials and methods). High quality BLAST matches are broken down by taxonomic category and only categories with proportions >1% are included. (C) Number of bacterial identified in each dataset after abundance filtering to ≥ 0.005%.
Fig 3
Fig 3. Differences in the abundance of organisms identified on $1 bills collected in Winter vs. Summer 2013.
(A) Proportion of human matches identified by megaBLAST-LCA for each time point. (B) Proportional distribution of non-human megaBLAST-LCA results. Low quality matches are defined as those filtered out prior to LCA analysis (see Materials and methods). High quality BLAST matches are broken down by taxonomic category and only categories with proportions >1% are included.
Fig 4
Fig 4. Relative abundance at the phylum and species level of bacterial taxa identified in the Winter and Summer 2013 datasets.
Relative abundance of the top 15 bacterial taxa at the species level for (A) Winter and (B) Summer. The color of each species corresponds to its respective phylum. Those species marked with a ** indicate species present in the most abundant of both time points.
Fig 5
Fig 5. Number and overlap of bacterial species identified on money by the sequence-based experiments (Winter and Summer) vs. bacterial species cultured then sequenced from LB media (Culture 1 and Culture 2).
Shaded area indicates species that were identified in all four experiments.

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Grant support

JMM is supported by the MacCracken Program in the Graduate School of Arts and Science at New York University. This study was funded by a New York University Grand Challenge project “Microbes, Sewage, Health and Disease: Mapping the New York City Metagenome” to JMC. IBM Almaden Research provided support in the form of salaries and computational resources for author RJP, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.
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