Characterization of airborne ice-nucleation-active bacteria and bacterial fragments

• Published in: Atmospheric environment (1994) Vol. 109; pp. 105 - 117
• Main Authors: Šantl-Temkiv, Tina, Sahyoun, Maher, Finster, Kai, Hartmann, Susan, Augustin-Bauditz, Stefanie, Stratmann, Frank, Wex, Heike, Clauss, Tina, Nielsen, Niels Woetmann, Sørensen, Jens Havskov, Korsholm, Ulrik Smith, Wick, Lukas Y., Karlson, Ulrich Gosewinkel
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2015
• Subjects: Aeromicrobiology; Airborne bacteria; Bioprecipitation; Ice nucleation; INA bacteria; Outer membrane vesicles; Pseudomonas; Airborne bacteria; Outer membrane vesicles; INA bacteria; Ice nucleation; Aeromicrobiology; Bioprecipitation
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2015.02.060

Some bacteria have the unique capacity of synthesising ice-nucleation-active (INA) proteins and exposing them at their outer membrane surface. As INA bacteria enter the atmosphere, they may impact the formation of clouds and precipitation. We studied members of airborne bacterial communities for their capacity to catalyse ice formation and we report on the excretion of INA proteins by airborne Pseudomonas sp. We also observed for the first time that INA biological fragments <220 nm were present in precipitation samples (199 and 482 INA fragments per L of precipitation), which confirms the presence of submicron INA biological fragments in the atmosphere. During 14 precipitation events, strains affiliated with the genus Pseudomonas, which are known to carry ina genes, were dominant. A screening for INA properties revealed that ∼12% of the cultivable bacteria caused ice formation at ≤−7 °C. They had likely been emitted to the atmosphere from terrestrial surfaces, e.g. by convective transport. We tested the ability of isolated INA strains to produce outer membrane vesicles and found that two isolates could do so. However, only very few INA vesicles were released per INA cell. Thus, the source of the submicron INA proteinaceous particles that we detected in the atmosphere remains to be elucidated. •Wet deposition of ice nucleation active (INA) Pseudomonas strains was observed.•Precipitation contained high density (199–482 L−1) of submicron INA cell fragments.•INA cells either had a long-distance continental or a local origin.•12% of all cultivable bacteria carried ina genes and were INA at ≤−7 °C.•Isolated INA strains excreted INA outer membrane vesicles at low concentrations.