Articles | Volume 15, issue 11
Atmos. Chem. Phys., 15, 6455–6465, 2015
Atmos. Chem. Phys., 15, 6455–6465, 2015

Research article 12 Jun 2015

Research article | 12 Jun 2015

Survival and ice nucleation activity of bacteria as aerosols in a cloud simulation chamber

P. Amato1,2, M. Joly1,2,3,4, C. Schaupp5, E. Attard1,2,*, O. Möhler5, C. E. Morris6, Y. Brunet7, and A.-M. Delort1,2 P. Amato et al.
  • 1CNRS, UMR 6296, ICCF, BP 80026, 63171 Aubière, France
  • 2Clermont University, Blaise Pascal University, Institute of Chemistry of Clermont-Ferrand (ICCF), BP 10448, 63000 Clermont-Ferrand, France
  • 3Clermont University, Blaise Pascal University, Observatory of Physics of the Globe of Clermont-Ferrand (OPGC), Laboratory of Physical Meteorology (LaMP), BP 10448, 63000 Clermont-Ferrand, France
  • 4CNRS, UMR 6016, LaMP/OPGC, BP 80026, 63171 Aubière, France
  • 5Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research, 76021 Karlsruhe, Germany
  • 6INRA, UR 407 Plant Pathology Research Unit, 84143 Montfavet, France
  • 7INRA, UMR 1391, ISPA, CS 20032, F-33882 Villenave d'Ornon CEDEX, France
  • *now at: Equipe Environnement et Microbiologie, UMR CNRS-IPREM 5254, Université de Pau et des Pays de l'Adour, IBEAS, BP 1155, 64013 Pau CEDEX, France

Abstract. The residence time of bacterial cells in the atmosphere is predictable by numerical models. However, estimations of their aerial dispersion as living entities are limited by a lack of information concerning survival rates and behavior in relation to atmospheric water. Here we investigate the viability and ice nucleation (IN) activity of typical atmospheric ice nucleation active bacteria (Pseudomonas syringae and P. fluorescens) when airborne in a cloud simulation chamber (AIDA, Karlsruhe, Germany). Cell suspensions were sprayed into the chamber and aerosol samples were collected by impingement at designated times over a total duration of up to 18 h, and at some occasions after dissipation of a cloud formed by depressurization. Aerosol concentration was monitored simultaneously by online instruments. The cultivability of airborne cells decreased exponentially over time with a half-life time of 250 ± 30 min (about 3.5 to 4.5 h). In contrast, IN activity remained unchanged for several hours after aerosolization, demonstrating that IN activity was maintained after cell death. Interestingly, the relative abundance of IN active cells still airborne in the chamber was strongly decreased after cloud formation and dissipation. This illustrates the preferential precipitation of IN active cells by wet processes. Our results indicate that from 106 cells aerosolized from a surface, one would survive the average duration of its atmospheric journey estimated at 3.4 days. Statistically, this corresponds to the emission of 1 cell that achieves dissemination every ~ 33 min m−2 of cultivated crops fields, a strong source of airborne bacteria. Based on the observed survival rates, depending on wind speed, the trajectory endpoint could be situated several hundreds to thousands of kilometers from the emission source. These results should improve the representation of the aerial dissemination of bacteria in numeric models.

Short summary
Mortality rate of typical bacterial aerosols (Pseudomonas species) was determined in a cloud simulation chamber. Ice nucleation activity remained unchanged for several hours in aerosolized cells, whether they were viable or not. Cloud increased the specific removal of ice nucleation active cells by precipitation. Survival was negatively impacted by the presence of cloud and by sulfates.
Final-revised paper