Membranes Are Decisive for Maximum Freezing Efficiency of Bacterial Ice Nucleators

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.

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High concentrations of biological aerosol particles and ice nuclei during and after rain

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-1767-2013 ◽

2013 ◽

Vol 13 (1) ◽

pp. 1767-1793 ◽

Cited By ~ 13

Author(s):

J. A. Huffman ◽

C. Pöhlker ◽

A. J. Prenni ◽

P. J. DeMott ◽

R. H. Mason ◽

...

Keyword(s):

Plant Pathogens ◽

Dna Analysis ◽

Fungal Spores ◽

Ice Nuclei ◽

Ice Nucleators ◽

Tightly Coupled ◽

High Concentrations ◽

Bacterial Aggregates ◽

Bacteria And Fungi ◽

Biological Aerosol Particles

Abstract. Bioaerosols are relevant for public health and may play an important role in the climate system, but their atmospheric abundance, properties and sources are not well understood. Here we show that the concentration of airborne biological particles in a forest ecosystem increases dramatically during rain and that bioparticles are closely correlated with atmospheric ice nuclei (IN). The greatest increase of bioparticles and IN occurred in the size range of 2–6 μm, which is characteristic for bacterial aggregates and fungal spores. By DNA analysis we found high diversities of airborne bacteria and fungi, including human and plant pathogens (mildew, smut and rust fungi, molds, Enterobacteraceae, Pseudomonadaceae). In addition to known bacterial and fungal IN (Pseudomonas sp., Fusarium sporotrichioides), we discovered two species of IN-active fungi that were not previously known as biological ice nucleators (Isaria farinosa and Acremonium implicatum). Our findings suggest that atmospheric bioaerosols, IN and rainfall are more tightly coupled than previously assumed.

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Supercooling Differences in the Eastern Subterranean Termite (Isoptera: Rhinotermitidae)

Journal of Entomological Science ◽

10.18474/0749-8004-39.4.525 ◽

2004 ◽

Vol 39 (4) ◽

pp. 525-536 ◽

Cited By ~ 3

Author(s):

Brian J. Cabrera ◽

Shripat T. Kamble

Keyword(s):

Atmospheric Pressure ◽

Reticulitermes Flavipes ◽

Biochemical Properties ◽

Subterranean Termite ◽

Control Groups ◽

Supercooling Point ◽

Ice Nucleators ◽

Laboratory Workers ◽

Eastern Subterranean Termite ◽

Termite Hindgut

Supercooling points were determined for untreated field-collected and untreated laboratory-maintained Reticulitermes flavipes (Kollar) workers and soldiers. Workers treated with antibiotics or had their hindgut-protozoa removed by exposing them to oxygen under pressure to determine the effects of absence of the hindgut fauna on supercooling. Supercooling points were compared between live and freshly-killed workers to determine whether supercooling in this species might be simply due to the biochemical properties of body fluids. Laboratory-maintained workers were also subjected to desiccation, starvation, or atmospheric pressure to determine their effects on supercooling. Supercooling points were lowest for laboratory workers treated with antibiotics and those that fed on brown paper-toweling for 7 d. Untreated field-collected workers had significantly higher supercooling points than untreated laboratory-maintained workers (−6.06 ± 0.79°C vs −9.29 ± 2.38°C, P < 0.0001). Both untreated field-collected and laboratory soldiers had significantly lower supercooling points than their respective workers (−7.39 ± 2.01°C vs −6.06 ± 0.79°C, P < 0.0001; and −11.60 ± 2.53°C vs −9.29 ± 2.38°C, P< 0.0001, respectively). There was no significant association between termite body mass and supercooling points for both laboratory and field termites (P= 0.0523 and P = 0.6242) or water content of laboratory termites and supercooling points (P = 0.1425). Defaunated workers had significantly lower supercooling points (−10.34 ± 2.38°C) than normally faunated workers (−9.48 ± 1.85°C)(P= 0.0095) suggesting that the symbiotic fauna may have higher supercooling points and act as ice nucleators in the termite hindgut. Starved and desiccated workers had significantly lower supercooling points (−10.38 ± 2.70°C and −10.39 ± 2.38°C, respectively) than their corresponding control groups (−9.87 ± 2.11°C and −9.89 ± 1.94°C; P = 0.0454; P = 0.0234, respectively) and untreated workers (−9.29 ± 2.38°C; P= 0.0021; P= 0.0011) suggesting that some forms of physical stress might lower the supercooling point.

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Understanding Bacterial Ice Nucleation

10.5194/egusphere-egu21-5614 ◽

2021 ◽

Author(s):

Ralph Schwidetzky ◽

Max Lukas ◽

Anna T. Kunert ◽

Ulrich Pöschl ◽

Janine Fröhlich-Nowoisky ◽

...

Keyword(s):

Electrostatic Interactions ◽

Affinity Purification ◽

Hydration Shell ◽

Three Dimensional ◽

American Chemical Society ◽

Chemical Society ◽

Ice Nucleation ◽

Dimensional Structure ◽

Protein Activity ◽

Ice Nucleators

Bacterial ice-nucleating proteins (INPs) promote heterogeneous ice nucleation better than any known material. On the molecular scale, bacterial INPs are believed to function by organizing water into ice&#8209;like patterns to enable the formation of embryonic crystals. However, the details of their working mechanism remains largely elusive. Here, we report the results of comprehensive evaluations of environmentally relevant effects such as changes in pH, the presence of ions and temperature on the activity, three-dimensional structure and hydration shell of bacterial ice nucleators using ice affinity purification, high-throughput ice nucleation assays and surface-specific sum-frequency generation spectroscopy.&#160;[1] Lukas, Max, et al. "Electrostatic Interactions Control the Functionality of Bacterial Ice Nucleators." Journal of the American Chemical Society 142.15 (2020): 6842-6846.[2] Lukas, Max, et al. "Interfacial Water Ordering Is Insufficient to Explain Ice-Nucleating Protein Activity." The Journal of Physical Chemistry Letters 12 (2020): 218-223.

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