A novel view on the mechanism of biological activity of antifreeze proteins

The adaptation of organisms to sub-zero temperatures is an intriguing problem in biology and biotechnology. The ice-binding antifreeze proteins are known to be responsible for the adaptation, but the mechanism of their action is still far from being clear. Here we show that: (i) in contrast to common belief, ice-binding proteins do not reduce the water freezing temperature and even raise the ice melting point; (ii) at sub-zero temperatures (to −30°C), ice can be formed only on ice-binding surfaces, but, for kinetic reasons, not in bulk water; (iii) living cells have some large surfaces, which can bind the antifreeze proteins. These facts allow suggesting that the task of antifreeze proteins is not to bind to the ice crystals already formed in the cell and stop their growth or rearrangement, but to bind to those cell surfaces where the ice nuclei can form, and thus to prevent ice formation completely.

Development and application of an integrated system of mathematical models for the transfer of radionuclides upon a hypothetic accident to minimize radioecological consequences

An integrated system of mathematic models is developed and implemented. The system is aimed at predicting the spread of the radioactive materials in the Arctic waters from a complex source distributed in space and time, formed by an emergency release of radionuclides from a nuclear-powered facility. Such approach allows taking into account various mechanisms of radionuclide transfer in arbitrary combinations. In addition to customary considered atmospheric and marine advection-diffusion processes with sedimentation on the underlying surface, it takes into consideration other mechanisms. Among them are particle sedimentation to the sea bottom with bottom capture, reverse process of washing-out from the bottom sediments. Specially attended is the Arctic-specific mechanism of particle ice-binding in the sea ice, drift of the frozen particles with ice, and their return to marine environment in result of ice thawing. The latter process may result in the appearance of the radioactive source at the large distance from the initial source and long time after the release event. The integrated model complex will provide the most realistic picture of the radioactive trace spread. It will sure be the effective tool for minimizing the emergency negative impact on the population and environment. The article a stage of long-term work that is currently ongoing.

Molecular evidence of intertidal habitats selecting for repeated ice-binding protein evolution in invertebrates

ABSTRACTIce-binding proteins (IBPs) have evolved independently in multiple taxonomic groups to improve their survival of sub-zero temperatures. Intertidal invertebrates in temperate and polar regions frequently encounter sub-zero temperatures, yet there is little information on IBPs in these organisms. We hypothesized that there are far more ice-binding proteins than are currently known and that the occurrence of freezing in the intertidal zone selects for these proteins. We compiled a list of genome-sequenced invertebrates across multiple habitats and a list of known IBP sequences and used BLAST to identify a wide array of putative IBPs in those invertebrates. We found that the probability of an invertebrate species having an ice-binding protein was significantly greater in intertidal species as compared to those primarily found in open ocean or freshwater habitats. These intertidal IBPs had high sequence similarity to fish and tick antifreeze glycoproteins and fish type II antifreeze proteins. Previously established classifiers based on machine learning techniques further predicted ice-binding activity in the majority of our newly identified putative IBPs. We investigated the potential evolutionary origin of one putative IBP from the hard-shelled mussel Mytilus coruscus and suggest that it arose through gene duplication and neofunctionalization. We show that IBPs likely readily evolve in response to freezing risk, that there is an array of uncharacterized ice binding proteins and highlight the need for broader laboratory-based surveys of the diversity of ice binding activity across diverse taxonomic and ecological groups.Summary statementIntertidal invertebrates have a disproportionate number of putative ice-binding proteins relative to other habitats. These putative proteins are highly similar to antifreeze glycoproteins and type II antifreeze proteins from fish.

Basidiomycetous Yeast, Glaciozyma antarctica, Forming Frost-Columnar Colonies on Frozen Medium

The basidiomycetous yeast, Glaciozyma antarctica, was isolated from various terrestrial materials collected from the Sôya coast, East Antarctica, and formed frost-columnar colonies on agar plates frozen at −1 °C. Thawed colonies were highly viscous, indicating that the yeast produced a large number of extracellular polysaccharides (EPS). G. antarctica was then cultured on frozen media containing red food coloring to observe the dynamics of solutes in unfrozen water; pigments accumulated in frozen yeast colonies, indicating that solutes were concentrated in unfrozen water of yeast colonies. Moreover, the yeast produced a small quantity of ice-binding proteins (IBPs) which inhibited ice crystal growth. Solutes in unfrozen water were considered to accumulate in the pore of frozen colonies. The extracellular IBPs may have held an unfrozen state of medium water after accumulation in the frost-columnar colony.

Within-Arctic horizontal gene transfer as a driver of convergent evolution in distantly related microalgae

The Arctic Ocean is being impacted by warming temperatures, increasing freshwater and highly variable ice conditions. The microalgal communities underpinning Arctic marine food webs, once thought to be dominated by diatoms, include a phylogenetically diverse range of small algal species, whose biology remains poorly understood. Here, we present genome sequences of a cryptomonad, a haptophyte, a chrysophyte, and a pelagophyte, isolated from the Arctic water column and ice. Comparing protein family distributions and sequence similarity across a densely-sampled set of algal genomes and transcriptomes, we note striking convergences in the biology of distantly related small Arctic algae, compared to non-Arctic relatives; although this convergence is largely exclusive of Arctic diatoms. Using high-throughput phylogenetic approaches, incorporating environmental sequence data from Tara Oceans, we demonstrate that this convergence was partly explained by horizontal gene transfers (HGT) between Arctic species, in over at least 30 other discrete gene families, and most notably in ice-binding domains (IBD). These Arctic-specific genes have been repeatedly transferred between Arctic algae, and are independent of equivalent HGTs in the Antarctic Southern Ocean. Our data provide insights into the specialised Arctic marine microbiome, and underlines the role of geographically-limited HGT as a driver of environmental adaptation in eukaryotic algae.

Analysis of the Sequence Characteristics of Antifreeze Protein

Antifreeze protein (AFP) is a proteinaceous compound with improved antifreeze ability and binding ability to ice to prevent its growth. As a surface-active material, a small number of AFPs have a tremendous influence on the growth of ice. Therefore, identifying novel AFPs is important to understand protein–ice interactions and create novel ice-binding domains. To date, predicting AFPs is difficult due to their low sequence similarity for the ice-binding domain and the lack of common features among different AFPs. Here, a computational engine was developed to predict the features of AFPs and reveal the most important 39 features for AFP identification, such as antifreeze-like/N-acetylneuraminic acid synthase C-terminal, insect AFP motif, C-type lectin-like, and EGF-like domain. With this newly presented computational method, a group of previously confirmed functional AFP motifs was screened out. This study has identified some potential new AFP motifs and contributes to understanding biological antifreeze mechanisms.