AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Hydrophilicity and CCN Activity of Atmospheric Bacteria Isolates and Implications for Cloud Formation
NATASHA DELEON-RODRIGUEZ, Aikaterini Bougiatioti, Nimmy Mathew, Arnaldo Negron-Marty, Michael Bergin, Konstantinos Konstantinidis, Athanasios Nenes, Georgia Institute of Technology
Abstract Number: 184 Working Group: Bioaerosols
Abstract The abundance of bacterial cells in the atmosphere can reach relatively high numbers, but the role of airborne cells in atmospheric chemistry, cloud formation, and precipitation remains to be quantified. A few studies exist that report the activity of bacterial cells as cloud condensation nuclei (CCN), and there is no understanding about the origin of this activity and its relation to the properties of a bacterial cell. The objective of this study was to determine whether the affinity of different bacterial cells to water (hydrophilicity) alone is sufficient to explain cell ability to act as CCN. To this end, we collected samples from rainwater and ambient air at different locations (urban cities and rain forest) and altitudes (>10 km and surface air). Over 20 bacterial isolates were obtained using different minimal and rich media and were identified based on sequencing of the 16S rRNA gene. Bacteria in rain samples from forested areas were typically known plant-associated bacteria, in contrast to those isolated from other environments, which were typically from soil. The hydrophilicity of different bacterial isolates was evaluated based on their contact angle with water. Measurements of contact angle were performed using a sessile drop over a bacterial lawn using a KSV CAM-200 goniometer. A wide range of contact angles were reported, ranging from very hydrophilic to very hydrophobic bacteria; the majority of the isolates however were found to be very hydrophilic. Finally, the CCN activity of each isolate is studied by introducing aerosolized bacteria into a continuous flow streamwise thermal-gradient CCN counter.