Polytrichum commune spores nucleate ice and associated microorganisms increase the temperature of ice nucleation activity onset

Abstract

Moss spores disperse via wind and have been found previously in precipitation and air samples. Their presence in the atmosphere led to this study's examining the potential of moss spores to contribute to ice nucleation, a process necessary for ice formation in clouds prior to precipitation. Ice nucleation assays were conducted using Polytrichum commune spores that were either associated with natural assemblages of microbes or extracted aseptically from capsules and subsequently confirmed to be free of culturable microbes. Liquid suspensions of capsule spores and non-sterile spores nucleated ice at temperatures as high as -12 and -7°C, respectively. When capsule and non-sterile spores were heated at 95°C for 10 min, which killed all culturable microbes on non-sterile spores, both nucleated ice from -10 to -13°C. An additional non-sterile spore sample collected from partially opened capsules in a forested ecosystem (ID, USA) nucleated ice at temperatures as high as -7°C, similar to non-sterile P. commune spores. This is the first set of results to indicate that P. commune spores themselves are capable of nucleating ice at temperatures higher than many abiological particles such as mineral dust (B-15°C) and that natural assemblages of microbes can increase their ice nucleation efficiency.Future studies aimed at determining the abundance of moss spores in the atmosphere and the identity of icenucleating microbes associated with them will provide further insights into the ability of moss spores to impact precipitation patterns.

Spatiotemporal patterns of microbial composition and diversity in precipitation

“…At temperatures warmer than À38°C, phase transition from liquid water to ice requires the presence of ice nucleating particles (INPs; Atkinson et al 2016, Kanji et al 2017, Knopf et al 2018. Various particles can act as ice nucleators (Szyrmer and Zawadzki 1997, Despr es et al 2012, Harrison et al 2016; however, those most efficient in catalyzing ice formation at warmer temperatures (>À15°C) are microbial or biogenic in origin (Murray et al 2012, Fr€ ohlich-Nowoisky et al 2015, Weber 2015, Hill et al 2017. Thus, knowledge concerning microbes in precipitation is potentially relevant to understanding global precipitation itself.…”

Surfaces of Silver Birch (<i>Betula pendula</i>) are Sources of Biological Ice Nuclei: <i>In-vivo</i> and <i>In-situ</i> Investigations

“…Heterogeneous ice nucleation regarding biological organisms has been reported in plants (Diehl et al, 2001;Pummer et al, 2012), bacteria (Lindow et al, 1982;Wolber et al, 1986), fungi (Pouleur et al, 1992;Fröhlich-Nowoisky et al, 2015;Kunert et al, 2019;Iannone et al, 2011;Haga et al, 2013), moss spores (Weber, 2016), and lichen (Kieft, 1988). Plants growing in temperate environments use mechanisms such as extracellular freezing (Burke et al, 1976;Storey and Storey, 2005;Pearce, 2001) or extra-organ freezing (Quamme, 1978;Ishikawa and Sakai, 1981) to survive sub-zero temperatures.…”

Heterogeneous Freezing of Liquid Suspensions Including Juices and Extracts from Berries and Leaves from Perennial Plants

“…INA has been found in nearly all kingdoms of life such as e.g., different bacteria [38,39], fungi [40,41] and fungal spores [42,43], moss spores [44], and lichen [45]. Biological particles, which are released in the atmosphere, can cover a wide range of possible substances (e.g., fragments of skin and plants, spores, pollen, proteins) and also over a wide range of sizes (from several nanometre up to the millimetre size range) [46].…”