Ice nucleation activity of bacteria isolated from snow compared with organic and inorganic substrates

Abstract

Environmental context. Biological ice nucleators have been found to freeze water at very warm temperatures. The potential of bio-aerosols to greatly influence cloud chemistry and microphysics is becoming increasingly apparent, yet detailed knowledge of their actual role in atmospheric processes is lacking. The formation of ice in the atmosphere has significant local, regional and global influence, ranging from precipitation to cloud nucleation and thus climate. Ice nucleation tests on bacteria isolated from snow and laboratory-grown bacteria, in comparison with those of known organic and inorganic aerosols, shed light on this issue. Abstract.Ice nucleation experiments on bacteria isolated from snow as well as grown in the laboratory, in comparison with those of known organic and inorganic aerosols, examined the importance of bio-aerosols on cloud processes. Snow samples were collected from urban and suburban sites in the greater Montreal region in Canada (45 • 28 N, 73 • 45 W). Among many snow bacterial isolates, eight types of bacterial species, none belonging to known effective ice nucleators such as Pseudomonas or Erwinia genera, were identified to show an intermediate range of ice nucleation activity (−12.9 ± 1.3 • C to −17.5 ± 2.8 • C). Comparable results were also obtained for molten snow samples and inorganic suspensions (kaolin and montmorillonite) of buffered water solutions. The presence of organic molecules (oxalic, malonic and succinic acids) had minimal effect (<2 • C) on ice nucleation. Considering experimental limitations, and drawing from observation in snow samples of a variety of bacterial populations with variable ice-nucleation ability, a shift in airborne-species population may significantly alter glaciation processes in clouds.

Laboratory Study of Effects of Atmospheric Pollutants on Ice Nucleation Activity of Bacteria

“…For the samples with PS concentrations less than 10 3 CFU/mL, the PS cells tend to be less than 10 for each droplet so that such droplets show less active. These results are not consistent with those reported by Mortazavi et al (2008). They showed that the low concentrations between 10 4 cells/mL and 10 2 cells/mL can also initiate droplet glaciations processes at temperature above -10°C (see Fig.…”

“…They showed that the low concentrations between 10 4 cells/mL and 10 2 cells/mL can also initiate droplet glaciations processes at temperature above -10°C (see Fig. 5, Mortazavi et al (2008)). We still cannot clearly figure out reasons for those different results.…”

“…Insoluble organic compounds may act as ice nuclei through heterogeneous nucleation. Some laboratory results have indicated that the low molecular weight soluble DCAs therefore do not play an important role in ice freezing processes (Du and Ariya, 2008;Mortazavi et al, 2008). Zobrist et al (2006) measured five low molecular weight carboxylic acids (oxalic, adipic, succinic, phthalic, fumaric) with the differential scanning calorimeter and concluded that only the dehydrate of oxalic acid can serve as a heterogeneous ice nuclei.…”

Primary biological aerosol particles in the atmosphere: a review

“…Species with intermediate IN activity begin ice nucleation only at lower temperatures (e.g. Mortazavi et al, 2008). A number of fungi (both free living and lichen fungi) were found to nucleate ice at temperatures comparable to INA bacteria (Table 6), some even at (18C.…”

Novel aerosol analysis approach for characterization of nanoparticulate matter in snow

“…Mineral dust is considered one of the most efficient ice forming nuclei, partly due to its abundance in global atmospheric aerosols. Certain marine-, vegetation-, and soil-derived aerosols, bacteria, fungi, and their fragments also efficiently nucleate ice (Bigg and Leck 2001;Fröhlich-Nowoisky et al 2014;Georgakopoulos et al 2009;Mortazavi et al 2014aMortazavi et al , b, 2015Mortazavi et al 2008;Schnell and Vali 1976;Vali et al 1976). Recently, research pointed to ice nucleating activity of nanosized organic compounds, possibly peptides, as well as nanosized inorganic compounds such as metal oxides .…”