AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Bacterial Metabolism in the Atmospheric Aerosol Microbiome: Missing Sink of Oxalate?
ALISON FANKHAUSER, Asher M. Krell, Simone J. Alston, Scott Banta, V. Faye McNeill, Columbia University
Abstract Number: 46 Working Group: Aerosol Chemistry
Abstract Live bacteria have been identified in cloud droplets, rainwater, and, more recently, small atmospheric aerosol particles at high altitudes. It is not known how the atmospheric environment impacts the life-cycle of these cells, or whether the metabolic activities of these cells have a meaningful impact on the chemistry of the aerosol particles. For example, oxalate is a common chemical component of atmospheric aerosols and cloud water, which is also a potential nutrient for bacteria which have been observed in aerosols aloft. Oxalate concentrations in marine boundary layer clouds have been observed to be an order of magnitude lower than model predictions based on molecular photochemistry alone (Crahan et al., 2004; Sorooshian et al., 2013). Metabolic activity of bacteria in aerosols or cloudwater may be a significant, as-yet uncharacterized sink of oxalate.
In order to investigate these issues, we performed laboratory experiments using model species which have been detected previously in atmospheric aerosol samples (Ralstonia eutropha, Cupriavidus oxalaticus), and modeling work. Bacteria tolerance to UV and fluctuations in physical conditions corresponding to different stages in the aerosol life cycle was tested. A flow cell system with constant circulation of fresh media was used to induce steady-state growth under a range of conditions relevant to atmospheric aerosols and quantify the metabolism of oxalate for different media conditions. The reaction rates and kinetics obtained from these experiments and literature studies have been implemented into GAMMA (McNeill et al. 2012), a kinetic model of atmospheric aerosol and cloudwater chemistry, in order to assess the impact of the bacterial metabolism on the composition of the atmospheric condensed phase.