Seasonal changes of airborne bacterial communities over Tokyo and influence of local meteorology

Abstract

14Recent progress in Next Generation Sequencing allows us to explore the diversity of airborne 15 microorganisms across time and space. However, few studies have used consecutive short-16 period samples to explore correlations between the seasonal variation of the microbiota and 17 meteorology. In order to understand airborne bacterial community dynamics over Tokyo, 18including fine-scale correlations between airborne microorganisms and meteorological 19 conditions, and the influence of local versus long-range transport of microbes, air samples 20 were continuously taken from a platform at the 458-m level of the Tokyo Skytree (a 634-m-21 high broadcasting tower in Tokyo) from August 2016 to February 2017. Predicted source 22 regions of airborne particles, from back trajectory analyses, changed abruptly from the 23 Pacific Ocean to the Eurasian Continent in the beginning of October. However, microbial 24 community composition and alpha and beta diversities were not affected by this 25 meteorological regime shift, suggesting that long-range transport from ocean or continent 26 was not the principal determinant controlling the local airborne microbiome. By contrast, 27 local meteorology, especially relative humidity and wind speed, had significant relationships 28 with both alpha diversities and beta diversity. Among four potential local source categories 29 (soil, bay seawater, river, and pond), bay seawater and soil were constant and predominant 30 sources. Statistical analyses suggest humidity is the most influential meteorological factor, 31 most likely because it is correlated with soil moisture and hence negatively correlated with 32 the dispersal of particles from the land surface. 33

Atmospheric Biodetection Part I: Study of Airborne Bacterial Concentrations from January 2018 to May 2020 at Saclay, France

“…For instance, in summer 2019, meteorological conditions were anticyclonic: low wind speed and instability in wind direction ( Figure A4 ). On a daily basis, the presence of short showers was negatively correlated with bacterial concentration due to wet deposition, which is consistent with observations made by the authors of [ 86 ]. Interestingly, the increase of bacterial concentration and fungal spores concentrations appears often just after the rain episode, as illustrated by Figure 10 , which is consistent with observations reported by the authors of [ 85 ].…”

“…Our observations also suggest that atmospheric concentrations of bacteria are strongly source-dependent and that the role of the rain needs to be better understood. Wind direction, temperature, and rain showers are the main drivers during the summer season, as reported by the authors of [ 86 , 89 ]. In particular, some species undergo strong differences in growth following wet, dry, or “splash” discharges.…”

Seasonal shift in airborne microbial communities

“…Previous investigations of the temporal variations of airborne microbial communities have consistently shown a seasonal shift in both cell concentration and community structure 2,[9][10][11][12] .…”

“…Thousands to millions of diverse microbial cells per cubic meter of air are transported among aerosols with their diversity shown to depend on geographic location 1 and time of year 2 . These microorganisms might be active, since some airborne microbial isolates were shown in laboratory studies to sustain metabolic activity using organic acids found in the atmosphere [3][4][5] .…”

“…Studies on airborne microbial communities at mid-latitude sites (aerosol-, cloud water-and precipitationassociated microorganisms) reported seasonal changes in both microbial biomass and biodiversity 2,[9][10][11][12][13] . The seasonal variability was associated to changes in surface conditions 10,11 , meteorological conditions 2,9 and/or changes in the global air circulation 9,13 . Yet, our understanding on how these potential factors impact airborne microbial community composition, and more specifically the microbial taxa individually, remains limited.…”