Culture-Independent Analysis of Aerosol Microbiology in a Metropolitan Subway System

Abstract

The goal of this study was to determine the composition and diversity of microorganisms associated with bioaerosols in a heavily trafficked metropolitan subway environment. We collected bioaerosols by fluid impingement on several New York City subway platforms and associated sites in three sampling sessions over a 1.5-year period. The types and quantities of aerosolized microorganisms were determined by culture-independent phylogenetic analysis of small-subunit rRNA gene sequences by using both Sanger (universal) and pyrosequencing (bacterial) technologies. Overall, the subway bacterial composition was relatively simple; only 26 taxonomic families made up ϳ75% of the sequences determined. The microbiology was more or less similar throughout the system and with time and was most similar to outdoor air, consistent with highly efficient air mixing in the system. Identifiable bacterial sequences indicated that the subway aerosol assemblage was composed of a mixture of genera and species characteristic of soil, environmental water, and human skin commensal bacteria. Eukaryotic diversity was mainly fungal, dominated by organisms of types associated with wood rot. Human skin bacterial species (at 99% rRNA sequence identity) included the Staphylococcus spp. Staphylococcus epidermidis (the most abundant and prevalent commensal of the human integument), S. hominis, S. cohnii, S. caprae, and S. haemolyticus, all well-documented human commensal bacteria. We encountered no organisms of public health concern. This study is the most extensive culture-independent survey of subway microbiota so far and puts in place pre-event information required for any bioterrorism surveillance activities or monitoring of the microbiological impact of recent subway flooding events.

Airborne Bacterial Communities of PM2.5 in Beijing-Tianjin-Hebei Megalopolis, China as Revealed by Illumina MiSeq Sequencing: A Case Study

“…The airborne bacterial diversity levels observed in BTH were higher than those reported in previous studies of coarse particulate matters (e.g., TSP or > 3 µm) collected from a high-elevation site and a metropolitan subway system (Bowers et al, 2009;Robertson et al, 2013). However, the diversity levels in BTH were lower than those reported in the urban aerosols (TSP) collected in both San Antonio and Austin (Brodie et al, 2007).…”

“…major genera in PM 2.5 in BTH. Some other soil-associated bacteria, such as Arthrobacter and Acinetobacter (Robertson et al, 2013) were also found in this study. The results further suggested that the soil might be another main source of bacteria in this study.…”

“…Meanwhile, plant, livestock and human pathogens are also dispersed through the atmosphere (Pillai and Ricke, 2002). Moreover, the large number of humans in public places in urban areas, such as Residents-CommercialTransportation Mixed Districts (RCTMD), maybe the key locales for natural pathogens transmission (Robertson et al, 2013). Therefore, it is important and necessary to investigate the diversity and composition of total airborne bacteria and the potential pathogens of PM 2.5 in urban areas.…”

“…Pyrosequencing has been applied to investigate the bacterial communities of air samples collected by using an air filtration collection system from a high-elevation site (3200 m) and three dominant land-use types (agricultural fields, suburban areas and forests) in Colorado, USA (Bowers et al, 2009;Bowers et al, 2010). Pyrosequencing has also been used to analyze the diversity of bioaerosols collected by fluid impingement (> 90% of the particles captured were > 3 µm) in a heavily trafficked metropolitan subway system in New York City, USA (Robertson et al, 2013). The Illumina Genome Analyser IIx sequencing (2 × 150 bp) has been applied to investigate the bacterial populations of total suspended particulate matter (TSP) collected in an urban area of Milan (Italy) (Bertolini et al, 2013).…”

Workshop on the Sources, Quantification and Health Implications of Bioaerosols Workshop Report

“…Sangersequencing strategies have been successfully used by Pashley et al (2012) and others (Robertson et al, 2013) for accurate fungal identification. However, this method is laborious, requiring the picking of multiple clones followed by ligation of the amplification product into a suitable vector, making it unsuitable for routine monitoring.…”