Characterization of bioaerosols associated with commuter transport micro-environments using high throughput sequencing

Air quality inside commuter transport is an important public health issue. However, there is currently limited information on commuter exposure to the microbial fraction of airborne particles (i.e. bioaerosols) in different types of transport. Here we investigated the abundance and diversity of bioaerosols in public trains and private automobiles in the UK using molecular approaches. Overall, bacterial 16S rRNA gene abundances were significantly greater with the train (between 3.07×10⁵ and 8.97×10⁵ copies/m³) compared to the car (between 4.21×10⁴ and 4.78×10⁵ copies/m³) (p-value 0.019 < 0.05), with no significant differences found with train journeys throughout the day (p-value >0.05). In terms of microbial composition, significant differences were found between the two modes of transport, for both bacterial and fungal communities. Specifically, bacteria were dominated by Proteobacteria (trains: 37 %; cars: 30 %), Firmicutes (trains: 20 %; cars: 36 %), Actinobacteria (trains: 34 %; cars: 16 %) and Bacteroidetes (trains: 6.1 %; cars: 13 %). Within the fungi, Ascomycota were predominant in the train (80 %), while the car was dominated by Basidiomycota (70 %), which may be due to the time of year sampled. Additionally, a core bacterial and fungal microbiome, including human commensals and outdoor-originating micro-organisms, alongside several taxa of human health concern were found in the air of both modes of transport. This study provides an important insight into the aerosol microbiome in transport micro-environments, which is crucial for the evaluation of commuter exposure to potential health risks.