Airborne Microbial Communities at High-Altitude and Suburban Sites in Toyama, Japan Suggest a New Perspective for Bioprospecting

Abstract

Airborne microorganisms, especially those at high altitude, are exposed to hostile conditions, including ultraviolet (UV) radiation, desiccation, and low temperatures. This study was conducted to compare the composition and abundance of airborne microorganisms at a high-altitude site, Mt. Jodo [2,839 m above mean sea level (AMSL)] and a suburban site (23 m AMSL) in Toyama, Japan. To our knowledge, this is the first study to investigate microbial communities in air samples collected simultaneously at two sites in relatively close proximity, from low and high altitude. Air samples were collected over a period of 3 years during 2009–2011. We then examined the bacterial and eukaryotic communities and estimated the abundance of bacteria and fungi with real-time TaqMan PCR. The airborne bacterial and eukaryotic communities differed between high-altitude and suburban sites on each sampling day. Backward trajectory analysis of air masses that arrived at high-altitude and suburban sites on each sampling day displayed almost the same paths. The bacterial communities were dominated by Actinobacteria, Firmicutes, and Proteobacteria, while the eukaryotic communities included Ascomycota, Basidiomycota, and Streptophyta. We also predicted some application of such microbial communities. The airborne bacterial and fungal abundance at the high-altitude site was about two times lower than that at the suburban site. These results showed that each airborne microbial communities have locality even if they are collected close location.

Size resolved characteristics of urban and suburban bacterial bioaerosols in Japan as assessed by 16S rRNA amplicon sequencing

“…The bacterial composition was congruent with those reported in other bioaerosol studies: with the airborne bacterial community dominated by Proteobacteria, Actinobacteria, and Firmicutes at the phylum level, and Actinobacteria, Alphaproteobacteria, Bacilli, Gammaproteobacteria, and Betaproteobacteria at the class level 16 , 17 , 19 – 22 .…”

“…Spatio-temporal variability of microbial communities is an important factor that provides insight into atmospheric biodiversity and biogeography 15 – 17 . In this study, we monitored the bacterial abundance and community composition of outdoor aerosol samples collected using size-resolved samplers at a suburban site in Toyama City and an urban site in Yokohama City, Japan.…”

Microbial Ecology of the Planetary Boundary Layer

“…In-flight collection of microorganisms in the upper troposphere and stratosphere remains expensive and an engineering challenge which, due to the likely very low cell concentrations in the stratosphere, suffers from aircraft-associated contamination [6,7,13]. It is likely that airborne microbial concentrations tend to decrease from the lower troposphere up to the upper troposphere [45] (up to fifteen kilometers) and the stratosphere [32,46] although the rate of decline is unknown. The vertical gradient in microbial concentration suggests that microbial cell fluxes might be upward in the atmosphere.…”

“…Reviews and field investigations that Subject to gravity, aerosols (or particulate matter) as well as bioaerosols become concentrated in the lower part of the troposphere that is called the planetary boundary layer (Figure 1). Microbial concentrations thus usually show a vertical stratification from the bottom to the top of the troposphere with average estimated bacterial concentrations of 9 × 10 2 − 2 × 10 7 cells/m 3 in the planetary boundary layer (based on six qPCR-based studies: [26][27][28][29][30][31] and 4 × 10 1 -8 × 10 4 cells/m 3 in the highest part of the troposphere called the free-troposphere (based on three qPCR-based studies [32][33][34]). Yet, microbial concentration estimations vary between investigations, which are based on different sampling strategies.…”

Seasonal Changes of the Airborne Microbiome in a Large Urban Area

“…The microbiome in the near surface atmosphere can be influenced by changes both from nearby sources and from environmental factors [1,21,40,67,73,74]. As a first characterization of diversity across space and time, we estimated two alpha-diversity indicators for each sample: number of taxa (richness, Chao 1 index [75]) and similarity in species relative abundance (evenness, Pielou's index [62]) (Methods).…”