AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Biological Ice Nucleation Activity in Cloud Water
Muriel Joly, Pierre Amato, Laurent Deguillaume, Eleonore Attard, Marie Monier, Cindy E. Morris, Martine Sancelme, ANNE-MARIE DELORT, Clermont Université, Institut de Chimie de Clermont-Ferrand
Abstract Number: 6 Working Group: Bioaerosols: Characterization and Environmental Impact
Abstract Ice nucleation active (INA) biological particles, in particular microorganisms, were studied in cloud water. Twelve cloud samples were collected over a period of 16 months from the puy de Dôme summit (1465 m, France) using sterile cloud droplet impactors. The samples were characterized through biological (cultures, cell counts) and physico-chemical measurements (pH, ion concentrations, carbon content…), and biological ice nuclei were investigated by droplet-freezing assays from -3°C to -13°C. The concentration of total INA particles within this temperature range typically varied from ~1 to ~100 per mL of cloud water; the concentrations of biological IN were several orders of magnitude higher than the values previously reported for precipitations. At -12°C, at least 76% of the IN were biological in origin, i.e. they were inactivated by heating at 95°C, and at temperatures above -8°C only biological material could induce ice. By culture, 44 Pseudomonas-like strains of bacteria were isolated from cloud water samples; 16% of them were found INA at the temperature of -8°C and they were identified as Pseudomonas syringae, Xanthomonas sp. and Pseudoxanthomonas sp.. Two strains induced freezing at as warm as -2°C, positioning them among the most active ice nucleators described so far. We estimated that, in average, 0.18% and more than 1%.of the bacterial cells present in clouds (~104 mL-1) are INA at the temperatures of -8°C and -12°C, respectively.
References:
- Attard E. et al. (2012) Effects of atmospheric conditions on ice nucleation activity of Pseudomonas. Atmospheric Chemistry and Physics 12, 10667-10677.
- Joly M. et al. Ice nucleation activity of bacteria isolated from cloud water, accepted in Atmospheric Environment.
- Vaïtilingom M. et al. (2012) Long-term features of cloud microbiology at the Puy de Dôme (France). Atmospheric Environment 56, 88-100.