The subway microbiome: seasonal dynamics and direct comparison of air and surface bacterial communities

Abstract

BackgroundMass transit environments, such as subways, are uniquely important for transmission of microbes among humans and built environments, and for their ability to spread pathogens and impact large numbers of people. In order to gain a deeper understanding of microbiome dynamics in subways, we must identify variables that affect microbial composition and those microorganisms that are unique to specific habitats.MethodsWe performed high-throughput 16S rRNA gene sequencing of air and surface samples from 16 subway stations in Oslo, Norway, across all four seasons. Distinguishing features across seasons and between air and surface were identified using random forest classification analyses, followed by in-depth diversity analyses.ResultsThere were significant differences between the air and surface bacterial communities, and across seasons. Highly abundant groups were generally ubiquitous; however, a large number of taxa with low prevalence and abundance were exclusively present in only one sample matrix or one season. Among the highly abundant families and genera, we found that some were uniquely so in air samples. In surface samples, all highly abundant groups were also well represented in air samples. This is congruent with a pattern observed for the entire dataset, namely that air samples had significantly higher within-sample diversity. We also observed a seasonal pattern: diversity was higher during spring and summer. Temperature had a strong effect on diversity in air but not on surface diversity. Among-sample diversity was also significantly associated with air/surface, season, and temperature.ConclusionsThe results presented here provide the first direct comparison of air and surface bacterial microbiomes, and the first assessment of seasonal variation in subways using culture-independent methods. While there were strong similarities between air and surface and across seasons, we found both diversity and the abundances of certain taxa to differ. This constitutes a significant step towards understanding the composition and dynamics of bacterial communities in subways, a highly important environment in our increasingly urbanized and interconnect world.

Effects of Bioaerosol Aerodynamic Size on Biodiversity in Three Kindergartens in Taiwan

“…In winter, windows in kindergarten A are commonly closed to keep the classrooms warm. The classrooms in kindergartens A and B are about 9.9*9.8*3.6 m 3 and are larger than those in kindergarten C, which are about 6.1*5.8*2.8 m 3 . In spring, the windows in kindergarten A are also usually closed to maintain a comfortable environment of recycled air using an air conditioner.…”

“…Only one colony was classified as Bacteroidetes (Weeksella virosa), which appeared in the 3 rd -stage plate (bacterial particle size range: 3.1 to 4.7 µm) from sampling round 4 (spring) at kindergarten C. The four phyla in the air samples (Table 1; Fig. 1) were the four most abundant phyla in the Oslo subway (air samples) [3] and a kindergarten in Oslo (floor dust samples) [6], but in a different order of relative abundance.…”

“…An investigation in Taiwan revealed remarkable seasonal variations of airborne fungus concentrations [1]; they vary significantly across seasons: bioaerosol samples in a subway in Norway were found to be more diverse in spring and summer than in autumn and winter [3]. In Taiwan, indoor ventilation conditions typically vary seasonally for climatic reasons.…”

Passenger-surface microbiome interactions in the subway of Mexico City

“…Microbial subway surfaces have been characterized previously in New York, Boston, Oslo, and México City (Afshinnekoo et al, 2015;Hsu et al, 2016;Gohli et al, 2019;Hernández et al, 2019). Additionally, the hand microbiome has been explored for Hong Kong subway passengers (Kang et al, 2018).…”

“…There are culture-independent studies of subway surfaces of New York City (Afshinnekoo et al, 2015), Boston (Hsu et al, 2016), Oslo (Gohli et al 2019), Mexico City (Hernández et al 2019), and by MetaSUB (MetaSUB International Consortium, 2016), an international initiative. Such studies have shown that the subway microbiome is structured mostly by commensal bacteria from the skin and that microbial composition and diversity vary according to the material and type of usage.…”