Vertical Distribution of Airborne Microorganisms Over Forest Environments: A Potential Source of Ice-Nucleating Bioaerosols

Date
2023-03-28
Authors
Maki, Teruya
Hosaka, Kentaro
Lee, Kevin C
Kawabata, Yasuhiro
Kajino, Mizuo
Uto, Maoto
Kita, Kazuyuki
Igarashi, Yasuhito
Supervisor
Item type
Journal Article
Degree name
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier BV
Abstract

Airborne microorganisms transported from forested areas can influence cloud formation by forming ice nuclei. However, the vertical transportation of airborne microorganisms over forested areas is not well understood. We collected aerosols at three heights, [ground (2 m), canopy top (20 m), and above canopy (500 m)] during the summer, fall and winter, to analyze the airborne microbial communities that were distributed vertically over the forest. During summer and fall, the microbial particles maintained similar concentrations in the forest zone (canopy top and ground) and decreased to 1/10th of the microbial concentration in the above canopy area. The particle concentrations in winter indicated efficient vertical mixing below 500 m. High-throughput DNA sequencing revealed that the airborne microbial communities were composed of terrestrial and phyllospheric species associated with the degradation of decaying plant litters. Regardless of the three seasons, the above canopy was dominated by atmospheric stress-resistant bacteria from the phyla Actinobacteria and Firmicutes. Unlike bacteria, the mushroom-type fungal members of Agaricomycetes grew in relative abundance above the canopy, primarily throughout the summer and winter, while mold-type fungal Dothideomycetes species were often found at all three heights during the fall. The Fusarium, Pseudomonas, and Bacillus isolates, which were obtained from air samples at three heights, indicated high activities of ice nucleation in the water-drop freezing assay. Therefore, ice-nucleating microbial taxa likely originated from fungal and bacterial communities in the soil litter and plant surfaces of the phyllospheric environments.

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Keywords
37 Earth Sciences , 3701 Atmospheric Sciences , 3702 Climate Change Science , Biotechnology , 0104 Statistics , 0401 Atmospheric Sciences , 0907 Environmental Engineering , Meteorology & Atmospheric Sciences , 3701 Atmospheric sciences , 3702 Climate change science , 4011 Environmental engineering
Source
Atmospheric Environment, ISSN: 1352-2310 (Print), Elsevier BV, 302, 119726-119726. doi: 10.1016/j.atmosenv.2023.119726
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