Low-temperature investigation of residual water bound in free-living Antarctic Prasiola crispa

Abstract

Antarctic algae are extremophilic organisms capable of surviving harsh environmental conditions such as low temperatures and deep dehydration. Although these algae have various adaptations for life in extreme environments, the majority of the molecular mechanisms behind their resistance to dehydration and freezing are not yet fully understood. The aim of our research was to observe the behaviour of bound water freezing in the free-living Antarctic alga Prasiola crispa. One way to avoid frost damage involves deep dehydration of the algal thallus. For that reason, a detailed analysis of water freezing at different sample hydration levels was carried out. Nuclear magnetic resonance investigation revealed two types of water immobilization: cooperative bound water freezing for samples with sample hydration levels above Δm/m0 = 0.40 and non-cooperative bound water immobilization for lower thallus hydration levels. In the differential scanning calorimetry experiment, 2-h incubation at -20°C suggested the diffusion and final binding of supercooled water to the ice nuclei and a lower hydration level threshold, at which ice formation could be observed (Δm/m0 = 0.21). Our research provides a new perspective on water sorption and freezing in Antarctic algae, which may be important not only in biological systems, but also in such novel materials as metal-organic frameworks or covalent organic frameworks.

Study of wheat (<i>Triticum aestivum</i> L.) seed rehydration observed by the Dent generalized model and ¹H-NMR relaxometry

“…( 9)). This approach has been shown to effectively describe FID signals in biological systems, these include Antarctic lichens or algae (Bacior et al, 2017(Bacior et al, , 2019(Bacior et al, , 2022, freeze-dried dipalmitoylphosphatidylcholine (DPPC) multilamellar membranes (Harańczyk et al, 2016), lyophilized photosynthetic lamellae (Harańczyk et al, 2015) or didecyldimethylammonium chloride modified DNA (Harańczyk et al, 2013). However, the model did not successfully fit the shape of the FID function for the dry wheat seed (Δm/m 0 < 0.128), particularly in the initial 80 µs of the NMR FID signal (Fig.…”

The outstanding capacity of Prasiola antarctica to thrive in contrasting harsh environments relies on the constitutive protection of thylakoids and on morphological plasticity

“…In 6). The capacity to withstand freezing temperatures down <À18°C is shared with other Antarctic species of the genus, such as P. crispa (Bacior et al, 2022;Becker, 1982;Fern andez-Mar ın, L opez-Pozo, et al, 2019;Kosugi et al, 2010), but the molecular mechanism enabling it are not yet fully understood (Bacior et al, 2022). The accumulation of compatible and soluble osmolytes, such as proline, seems to be part of the biochemical mechanism enabling freezing tolerance in P. crispa (Jackson & Seppelt, 1995).…”

“…Most species are well photoprotected against UV-radiation (Hartmann et al, 2016;Lud et al, 2001) and against excess of visible radiation too (Kosugi et al, 2020). The species with polar distribution are additionally highly tolerant to freezing (Bacior et al, 2022;Fern andez-Mar ın, L opez-Pozo, et al, 2019) associated with nitrogen-rich deposits (Abakumov et al, 2021;Holzinger et al, 2006;Lud et al, 2001). Notably, green algae species of the genus Prasiola are widely distributed at many terrestrial and supralittoral sites (Broady, 1989), being especially abundant near ornithogenic soils (Abakumov et al, 2021;Smith & Gremmen, 2001) and, even though their production rate is lower than the one of mosses (the main primary producers in Antarctica together with lichens), they are important food sources and habitat for primary consumers along with microflora (Davis, 1981;Lukashanets et al, 2022).…”

“…Most species are well photoprotected against UV‐radiation (Hartmann et al., 2016; Lud et al., 2001) and against excess of visible radiation too (Kosugi et al., 2020). The species with polar distribution are additionally highly tolerant to freezing (Bacior et al., 2022; Fernández‐Marín, López‐Pozo, et al., 2019) and very frequently associated with nitrogen‐rich deposits (Abakumov et al., 2021; Holzinger et al., 2006; Lud et al., 2001).…”