Airborne bacteria that nucleate ice at relatively warm temperatures (>-10°C) can interact with cloud water droplets, affecting the formation of ice in clouds and the residency time of the cells in the atmosphere. We sampled 65 precipitation events in southeastern Louisiana over 2 years to examine the effect of season, meteorological conditions, storm type, and ecoregion source on the concentration and type of ice-nucleating particles (INPs) deposited. INPs sensitive to heat treatment were inferred to be biological in origin, and the highest concentrations of biological INPs (∼16,000 INPs liter-1 active at ≥-10°C) were observed in snow and sleet samples from wintertime nimbostratus clouds with cloud top temperatures as warm as -7°C. Statistical analysis revealed three temperature classes of biological INPs (INPs active from -5 to -10°C, -11 to -12°C, and -13 to -14°C) and one temperature class of INPs that were sensitive to lysozyme (i.e., bacterial INPs, active from -5 to -10°C). Significant correlations between the INP data and abundances of taxa in the Bacteroidetes, Firmicutes, and unclassified bacterial divisions implied that certain members of these phyla may possess the ice nucleation phenotype. The interrelation between the INP classes and fluorescent dissolved organic matter, major ion concentrations (Na+, Cl-, SO4 2-, and NO3 -), and backward air mass trajectories indicated that the highest concentrations of INPs were sourced from high-latitude North American and Asian continental environments, whereas the lowest values were observed when air was sourced from marine ecoregions. The intra- and extracontinental regions identified as sources of biological INPs in precipitation deposited in the southeastern United States suggests that these bioaerosols can disperse and affect meteorological conditions thousands of kilometers from their terrestrial points of origin.IMPORTANCE The particles most effective at inducing the freezing of water in the atmosphere are microbiological in origin; however, information on the species harboring this phenotype, their environmental distribution, and ecological sources are very limited. Analysis of precipitation collected over 2 years in Louisiana showed that INPs active at the warmest temperatures were sourced from terrestrial ecosystems and displayed behaviors that implicated specific bacterial taxa as the source of the ice nucleation activity. The abundance of biological INPs was highest in precipitation from winter storms and implied that their in-cloud concentrations were sufficient to affect the formation of ice and precipitation in nimbostratus clouds.
Keywords: aeromicrobiology; bacteria; biological ice nuclei; environmental microbiology; meteorology; microbial ecology; precipitation.
Copyright © 2019 American Society for Microbiology.
Biogenic Sources of Ice Nucleating Particles at the High Arctic Site Villum Research Station.Environ Sci Technol. 2019 Sep 17;53(18):10580-10590. doi: 10.1021/acs.est.9b00991. Epub 2019 Aug 28. Environ Sci Technol. 2019. PMID: 31094516
How Does a Raindrop Grow?: Precipitation in natural clouds may develop from ice crystals or from large hygroscopic aerosols.Science. 1959 Jan 16;129(3342):123-9. doi: 10.1126/science.129.3342.123. Science. 1959. PMID: 17745322
Terrestrial Origin for Abundant Riverine Nanoscale Ice-Nucleating Particles.Environ Sci Technol. 2018 Nov 6;52(21):12358-12367. doi: 10.1021/acs.est.8b03881. Epub 2018 Oct 12. Environ Sci Technol. 2018. PMID: 30264996
Marine Aerosols and Clouds.Ann Rev Mar Sci. 2018 Jan 3;10:289-313. doi: 10.1146/annurev-marine-121916-063148. Epub 2017 Oct 13. Ann Rev Mar Sci. 2018. PMID: 29029576 Review.
Bacterial ice nucleation: significance and molecular basis.FASEB J. 1993 Nov;7(14):1338-43. doi: 10.1096/fasebj.7.14.8224607. FASEB J. 1993. PMID: 8224607 Review.