Title:
Toward Quantifying the Patterns of Bacteria and Fungi in the Atmosphere and their Functional Role in Cloud Formation Via Ice Nucleation
Toward Quantifying the Patterns of Bacteria and Fungi in the Atmosphere and their Functional Role in Cloud Formation Via Ice Nucleation
Author(s)
Davila Santiago, Lizbeth
Advisor(s)
Konstantinidis, Kostas T.
Editor(s)
Collections
Supplementary to
Permanent Link
Abstract
The atmosphere has received little attention for its biological component, especially when compared to its physical and chemical components. The study of bioaerosols and their relationship with the atmosphere has gained particular attention in the last couple decades because accumulating evidence suggests that bioaerosols may interact with the atmosphere, biosphere, weather, and public health. Moreover, the role of airborne cells in cloud formation and precipitation by serving as precursors for ice nucleation or ice nuclei (IN) at warmer temperatures than abiotic particles (e.g. dust) has been recognized. Even though the atmosphere is a hostile environment for living organisms (e.g., stress caused by low temperatures, high UV-radiation, pH changes, oxidative and osmotic stress, amongst others), microorganisms are present and relatively abundant (e.g., 102 -106 cell/m3) in the atmosphere. However, the effects of common atmospheric conditions (some mentioned above) on microbial community patterns and on the ice nucleation activity of IN bacterial species remain poorly understood. Therefore, a major objective of this study was to establish microbial (bacteria and fungi) compositional and diversity patterns between dry-air and rain samples collected in an urban setting (Metro Atlanta) over two consecutive years with culture-independent techniques and amplicon sequencing. The results revealed significant changes in community structure among sample types, including pathogenic and/or allergen fraction of the community, but not strong seasonality. Furthermore, the ice nucleation activity of three different bacterial IN species (Pseudomonas syringae (Gram -), Lysinibacillus parviboronicapiens (Gram +), and Xanthomonas campestris (Gram -) after exposure to a range of acidity, oxidative and UV radiation stressors and a combination of them by immersion freezing testing. Bacterial and fungal communities in dry-air samples do not appear to mirror the same community structure of rain samples, and seasonality is not a strong factor in shaping the microbial community of the atmosphere in a subtropical climate as Metro Atlanta. Pseudomonas syringae, and to a lesser extent the other two species evaluted, retained efficient ice nucleation activity (T50 above -10ºC; T50 represents the temperature that 50% of the water droplets froze as an effect of the present of the cells) even after viability loss due to acidic pH (pH = 2.5). Collectively, this research provides new insights into the public health aspect of bioaerosols as well as their role in weather/climate patterns.
Sponsor
Date Issued
2023-04-27
Extent
Resource Type
Dissertation