Please mark your calendar for Arnaldo Negrón Marty’s defense presentation.  The defense will be held on November 4th at 10 am in ES&T L1114

Title: Understanding bioaerosols atmospheric lifecycle, abundance variability and impacts

Committee members: Dr. Athanasios Nenes (Advisor), Dr. Rodney Weber, Dr. Konstantinos Konstantinidis, Dr. Jennifer Glass and Dr. Ellery Ingall

Abstract: Bioaerosols are ubiquitous in the atmosphere with potential impacts on human health, cloud formation, and biogeochemical cycles. Measuring bioaerosols poses a challenge for established biological tools owing to their low atmospheric concentration. Bioaerosols are often quantified by light-induced fluorescence (LIF) instrumentation, but the frequency of misidentification of abiotic particles by LIF is high and variable. As a result, a robust protocol using a state-of-the-art cyclone to collect liquid samples and subsequent flow cytometry (FCM) analysis, an established single-cell detection technique, was effectively designed and applied to quantify bioaerosol populations in various environments. In Metro Atlanta, bioaerosol dynamics are influenced by meteorology, as a high nucleic acid population (e.g. wet-ejected fungal spores) is enhanced on humid and warm days after rain events and FCM results agree with LIF observations. Then, during the airborne deployment at the California Coast bacteria-like particles enhanced in the marine free troposphere, suggesting unique capabilities in microbes allowing them to stay airborne compared to their abiotic counterpart. In the Eastern Mediterranean, bioaerosol is dominated by an LNA population and may be enhanced during dust events, but the estimated amount of bioavailable phosphorus likely provided by bioaerosols upon deposition is considerably lower than dust contribution to Eastern Mediterranean Sea as calculated by global models. Finally, we studied the response of intact microbial cells, a major component of bioaerosol, to multiple acidity levels (pH) by quantifying their viability and ability to express ice nucleation capacity in a newly designed immersion freezing chamber. Notably, ice active Pseudomonas syringae strain previously exposed to highly acidic conditions freezes at high subzero temperatures even when cells lost viability. Overall, the optimization of detection and quantification techniques has shown that bioaerosol is a core component of atmospheric aerosol with unique and robust impacts on clouds and biogeochemical cycles.