AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Cloud Condensation and Ice Nucleation Phenotypic Analyses of Taxonomically Diverse Bacteria Isolated from Rainwater
SAMANTHA M. WATERS, Sara Purdue, Smruthi Karthikeyan, James Hite, Kostas Konstantinidis, Athanasios Nenes, Georgia Institute of Technology
Abstract Number: 390 Working Group: Bioaerosols
Abstract Bacteria are ubiquitous in the environment, including the atmosphere, and are capable of influencing their surroundings. While it is known that some bacteria are capable of ice formation when studied by immersion freezing (INA), characterization of cloud condensation activity (CCN) of bacteria is sparser. Additionally, most studies on these two phenotypes in bacteria is limited to very select taxonomic lineages. Bacteria are large and theoretically expected to condense water at much lower super-saturation conditions than some other aerosols, irrespective of their exterior chemistries. Therefore, it is important to empirically characterize the CCN activity and subsequent INA of taxonomically diverse bacteria. And, as bacteria vary in size from submicron to super-micron in size, depending on the species, it is of interest to understand underlying, extracellular chemistries when comparing bacteria of similar size. This interdisciplinary study employed a combination of laboratory techniques and environmental sampling to investigate the CCN and IN phenotypes of bacterial isolates collected in urban Atlanta, GA. Briefly, approximately 100 bacterial isolates from rainwater were taxonomically identified based on 16S rRNA sequencing. Interesting and previously uncharacterized bacteria (~25 isolates) were chosen from the isolates collected and phenotypic investigation of CCN and IN activity was performed. CCN experiments were conducted using a DMT Continuous Flow Streamwise Thermal Gradient CCN counter across a range of super-saturation conditions. For INA of the bacterial isolates, a droplet freezing assay (DFA) previously developed in the laboratory was used to measure immersion freezing activity of the isolates. Here we present exhaustively collected, empirical data on the cloud condensation and ice nucleation activity of the bacteria. Our CCN results agree strongly with theory, size is important even in biological surfaces; submicron bacteria, irrespective of chemistry, activate at higher supersaturation conditions than supermicron bacteria.