Evaluating the potential for Haloarchaea to serve as ice nucleating particles

Jessie M Creamean,Paul J Demott,Matthew E Rhodes,Allyson D Pace,Julio E Ceniceros,Thomas C J Hill,Lilyanna Newman

doi:10.5194/bg-18-3751-2021

Abstract

Abstract. Aerosols play a crucial role in cloud formation. Biologically derived materials from bacteria, fungi, pollen, lichen, viruses, algae, and diatoms can serve as ice nucleating particles (INPs), some of which initiate glaciation in clouds at relatively warm freezing temperatures. However, determining the magnitude of the interactions between clouds and biologically derived INPs remains a significant challenge due to the diversity and complexity of bioaerosols and limited observations of such aerosols facilitating cloud ice formation. Additionally, microorganisms from the domain Archaea have, to date, not been evaluated as INPs. Here, we present the first results reporting the ice nucleation activity of four species in the class Haloarchaea. Intact cells of Halococcus morrhuae and Haloferax sulfurifontis demonstrated the ability to induce immersion freezing at temperatures up to −18 ∘C, while lysed cells of Haloquadratum walsbyi and Natronomonas pharaonis were unable to serve as immersion INPs. Exposure to heat and peroxide digestion indicated that the INPs of intact cells were driven by organic (H. morrhuae and H. sulfurifontis) and possibly also heat labile materials (H. sulfurifontis only). While halophiles are prominent in hypersaline environments such as the Great Salt Lake and the Dead Sea, other members of the Archaea, such as methanogens and thermophiles, are prevalent in anoxic systems in seawater, sea ice, marine sediments, glacial ice, permafrost, and other cold niches. Archaeal extremophiles are both diverse and highly abundant. Thus, it is important to assess their ability to serve as INPs as it may lead to an improved understanding of biological impacts on clouds.

Highlights

Through their impact on the atmospheric energy budget and hydrological cycle, clouds play a prominent role in shaping Earth’s climate at both global and regional scales (Baker and Peter, 2008; Boucher et al, 2013)
The associated saline medias were prepared for H. morrhuae, H. sulfurifontis, H. walsbyi, and N. pharaonis with the following alterations: (1) for medium 97, only 150 g of NaCl was added instead of 250 g NaCl for the growth of H. morrhuae, and (2) 1 g L−1 of glycerol was supplemented to medium 1091 for the growth of H. walsbyi
One possible explanation is that H. morrhuae is unusual among the Archaea in that it has a cell envelope composed of polysaccharides, which have been shown to serve as tracers for ice nucleating activity (Zeppenfeld et al, 2019)

Summary

Introduction

Through their impact on the atmospheric energy budget and hydrological cycle, clouds play a prominent role in shaping Earth’s climate at both global and regional scales (Baker and Peter, 2008; Boucher et al, 2013). At temperatures greater than −38 ◦C, the assistance of INPs, such as mineral dust, volcanic ash, and select biologically produced macromolecules (e.g., from pollen, fungi, bacteria, and other sources), is required to initiate the heterogeneous formation of primary ice embryos that continue to grow into larger ice crystals (Hoose and Möhler, 2012; Kanji et al, 2017).

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Conclusion