title: Characterization of ice-nucleating bacteria using on-line electron impact ionization aerosol mass spectrometry.
abstract: The mass spectral signatures of airborne bacteria were measured and analyzed in cloud simulation experiments at the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) facility. Suspensions of cultured cells in pure water were sprayed into the aerosol and cloud chambers forming an aerosol which consisted of intact cells, cell fragments and residual particles from the agar medium in which the bacteria were cultured. The aerosol particles were analyzed with a high-resolution time-of-flight aerosol mass spectrometer equipped with a newly developed PM2.5 aerodynamic lens. Positive matrix factorization (PMF) using the multilinear engine (ME-2) source apportionment was applied to deconvolve the bacteria and agar mass spectral signatures. The bacteria mass fraction contributed between 75 and 95% depending on the aerosol generation, with the remaining mass attributed to agar. We present mass spectra of Pseudomonas syringae and Pseudomonas fluorescens bacteria typical for ice-nucleation active bacteria in the atmosphere to facilitate the distinction of airborne bacteria from other constituents in ambient aerosol, e.g. by PMF/ME-2 source apportionment analyses. Nitrogen-containing ions were the most salient feature of the bacteria mass spectra, and a combination of C4 H8 N(+) (m/z 70) and C5 H12 N(+) (m/z 86) may be used as marker ions.
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, CH-5232, Villigen PSI, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Wolf
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, CH-5232, Villigen PSI, Switzerland.
authors.forename: J G
authors.initials: JG
authors.lastname: Slowik
authors.affiliation: Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Schaupp
authors.affiliation: National Center for Scientific Research, Institute of Chemistry of Clermont-Ferrand, 63000, Clermont-Ferrand, France.
authors.forename: P
authors.initials: P
authors.lastname: Amato
authors.affiliation: Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Saathoff
authors.affiliation: Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Möhler
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, CH-5232, Villigen PSI, Switzerland.
authors.forename: A S H
authors.initials: AS
authors.lastname: Prévôt
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, CH-5232, Villigen PSI, Switzerland.
authors.forename: U
authors.initials: U
authors.lastname: Baltensperger
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D001419:Bacteria / Q000737:chemistry*; D001426:Bacterial Proteins / Q000032:analysis / Q000737:chemistry; D004583:Electrons; D007053:Ice; D013058:Mass Spectrometry / Q000379:methods*
chemical_list: D000336:Aerosols; D001426:Bacterial Proteins; D007053:Ice
keywords: aerosol mass spectrometry; amino acids; bacteria; bioaerosols; electron impact ionization; proteins