The Influence of Various Freezing-thawing Methods of Skin on Drug Permeation and Skin Barrier Function.

The selection of skin is crucial for the in vitro permeation test (IVPT). The purpose of this study was to investigate the influence of different freezing-thawing processes on the barrier function of skin and the transdermal permeability of granisetron and lidocaine. Rat and hairless mouse skins were thawed at three different conditions after being frozen at -20℃ for 9 days: thawed at 4℃, room temperature (RT), and 32℃. There were no significant differences in the steady-state fluxes of drugs between fresh and thawed samples, but compared with fresh skin there were significant differences in lag time for the permeation of granisetron in rat skins thawed at RT and 32℃. Histological research and scanning electron microscopy images showed no obvious structural damage on frozen/thawed skin, while immunohistochemical staining and enzyme-linked immunosorbent assay for the tight junction (TJ) protein Cldn-1 showed significantly impaired epidermal barrier. It was concluded that the freezing-thawing process increases the diffusion rate of hydrophilic drugs partly due to the functional degradation of TJs. It's recommended that hairless, inbred strains and identical animal donors should be used, and the selected thawing method of skin should be validated prior to IVPT, especially for hydrophilic drugs.

Proteomic analysis of Rana sylvatica reveals differentially expressed proteins in liver in response to anoxia, dehydration or freezing stress.

Ectothermic animals that live in seasonally cold regions must adapt to seasonal variation and specific environmental conditions. During the winter, some amphibians hibernate on land and encounter limited environmental water, deficient oxygen, and extremely low temperatures that can cause the whole body freezing. These stresses trigger physiological and biochemical adaptations in amphibians that allow them to survive. Rana sylvatica, commonly known as the wood frog, shows excellent freeze tolerance. They can slow their metabolic activity to a near halt and endure freezing of 65-70% of their total body water as extracellular ice during hibernation, returning to normal when the temperatures rise again. To investigate the molecular adaptations of freeze-tolerant wood frogs, a comprehensive proteomic analysis was performed on frog liver tissue after anoxia, dehydration, or freezing exposures using a label-free LC-MS/MS proteomic approach. Quantitative proteomic analysis revealed that 87, 118, and 86 proteins were significantly upregulated in dehydrated, anoxic, and frozen groups, suggesting potential protective functions. The presence of three upregulated enzymes, glutathione S-transferase (GST), aldolase (ALDOA), and sorbitol dehydrogenase (SORD), was also validated. For all enzymes, the specific enzymatic activity was significantly higher in the livers of frozen and anoxic groups than in the controls. This study reveals that GST, ALDOA, and SORD might participate in the freeze tolerance mechanism by contributing to regulating cellular detoxification and energy metabolism.

Autophagy is suppressed by low temperatures and is dispensable for cold acclimation in Arabidopsis.

Plants have evolved various mechanisms to adapt to the ever-changing external environment. Autophagy is one such mechanism and has been suggested to play a key role in responding to and adapting to abiotic stresses in plants. However, the role of autophagy in adaptation to cold and freezing stresses remains to be characterized in detail. Here, we investigated the role of autophagy in the low-temperature response of Arabidopsis using atg mutants. Both the atg5-1 and atg10-1 mutants exhibited normal freezing tolerance, regardless of cold acclimation. A comparison of fresh weights indicated that the difference in growth between the wild-type and atg plants under cold conditions was rather small compared with that under normal conditions. Analysis of COLD-REGULATED gene expression showed no significant differences between the atg mutants and wild type. Treatment with 3-methyladenine, an inhibitor of autophagy, did not impair the induction of COR15Apro::LUC expression upon exposure to low temperature. Evaluation of autophagic activity using transgenic plants expressing RBCS-mRFP demonstrated that autophagy was rarely induced by cold exposure, even in the dark. Taken together, these data suggest that autophagy is suppressed by low temperatures and is dispensable for cold acclimation and freezing tolerance in Arabidopsis.

Predicting soil thermal properties in freeze-thaw cycles using EFAttNet: A comparative analysis.

This study investigates the thermal conductivity (λ) and volumetric heat capacity (C) of sandy soil samples under a variety of conditions, including freeze-thaw cycles at temperatures both above and below zero and differing moisture levels. To estimate these thermal properties, a novel predictive model, EFAttNet, was developed, which utilizes custom-designed embedding and attention-based fusion networks. When compared to traditional de Vries empirical models and other baseline algorithms, EFAttNet demonstrated superior accuracy. Preliminary measurements showed that λ values increased linearly with moisture content but decreased with temperature, whereas C values exhibited a rising trend with both moisture content and freezing temperature. Following freeze-thaw cycles, both λ and C were positively influenced by moisture content and freezing temperature. The EFAttNet-based model proved highly accurate in predicting thermal properties, particularly effective at capturing nonlinear relationships among the influencing factors. Among these factors, the degree of saturation had the most significant impact, followed by the number of freeze-thaw cycles, subzero temperatures, porosity, and moisture content. Notably, dry density exerted minimal influence on thermal properties, likely due to the overriding effects of other factors or specific soil characteristics, such as particle size distribution or mineralogical composition. These findings have significant implications for construction and engineering projects, especially in terms of sustainability and energy efficiency. The demonstrated accuracy of the EFAttNet-based model in estimating thermal properties under various conditions holds promise for practical applications. Although focused on specific soil types and conditions, the insights gained can guide further research and development in managing soil thermal properties across diverse environments, thereby enhancing our understanding and application in this field.

Assessment of fecal bacterial viability and diversity in fresh and frozen fecal microbiota transplant (FMT) product in horses.

BACKGROUND: Currently, lack of standardization for fecal microbiota transplantation (FMT) in equine practice has resulted in highly variable techniques, and there is no data on the bacterial metabolic activity or viability of the administered product. The objectives of this study were to compare the total and potentially metabolically active bacterial populations in equine FMT, and assess the effect of different frozen storage times, buffers, and temperatures on an equine FMT product. Fresh feces collected from three healthy adult horses was subjected to different storage methods. This included different preservation solutions (saline plus glycerol or saline only), temperature (-20 °C or -80 °C), and time (fresh, 30, 60, or 90 days). Samples underwent DNA extraction to assess total bacterial populations (both live and dead combined) and RNA extraction followed by reverse transcription to cDNA as a proxy to assess viable bacteria, then 16s rRNA gene amplicon sequencing using the V1-V2 region. RESULTS: The largest difference in population indices and taxonomic composition at the genus level was seen when evaluating the results of DNA-based (total) and cDNA-based (potentially metabolically active) extraction method. At the community level, alpha diversity (observed species, Shannon diversity) was significantly decreased in frozen samples for DNA-based analysis (P < 0.05), with less difference seen for cDNA-based sequencing. Using DNA-based analysis, length of storage had a significant impact (P < 0.05) on the bacterial community profiles. For potentially metabolically active populations, storage overall had less of an effect on the bacterial community composition, with a significant effect of buffer (P < 0.05). Individual horse had the most significant effect within both DNA and cDNA bacterial communities. CONCLUSIONS: Frozen storage of equine FMT material can preserve potentially metabolically active bacteria of the equine fecal microbiome, with saline plus glycerol preservation more effective than saline alone. Larger studies are needed to determine if these findings apply to other individual horses. The ability to freeze FMT material for use in equine patients could allow for easier clinical use of fecal transplant in horses with disturbances in their intestinal microbiome.

Evaluation of the effectiveness of the use of exosomes in the regulation of the mitochondrial membrane potential of frozen/thawed spermatozoa.

Numerous studies confirm the involvement of extracellular vesicles (EVs) in the regulation of physiological processes of mammalian sperm cells. It has been proven that they take part in the processes of capacitation, acrosonmal reaction, and anti-oxidation. Despite growing interest in the biomedical potential (including the search for new reproductive biomarkers) of EVs, the role of extracellular seminal vesicles in maintaining semen quality during cryopreservation has not yet been established. Therefore, the objective of this experiment was to evaluate the effectiveness of the use in the regulation of the mitochondrial membrane potential of bovine sperm and to explain the mechanisms of EV action during cell cryopreservation. Exosomes were isolated from bull semen plasma, measured, and used for extender supplementation. Semen samples were collected from Simmental bulls, diluted, and pre-evaluated. Then they were divided into equal fractions that did not contain EVs or were supplemented with 0.75; 1.5 and 2.25 mg/ml of EVs. The test samples were frozen/thawed and the mitochondrial membrane potential, DNA integrity, and viability were evaluated. EVs have been established to have a positive effect on cryopreserved sperm structures. The most favourable level of EVs was 1.5 mg / ml, which can be successfully to improve cell cryostability during freezing/thawing. In this study, exosomes isolated from the sperm plasma and supplemented with a concentrated dose in the extender for sperm freezing were shown to significantly improve cryostability of cells by supporting the potentials of the mitochondrial membrane and protecting the cytoplasmic membrane of spermatozoa.

High-speed cryo-microscopy reveals that ice-nucleating proteins of Pseudomonas syringae trigger freezing at hydrophobic interfaces.

Ice-nucleating proteins (INpro) trigger the freezing of supercooled water droplets relevant to atmospheric, biological, and technological applications. The high ice nucleation activity of INpro isolated from the bacteria Pseudomonas syringae could be linked to the aggregation of proteins at the bacterial membrane or at the air-water interface (AWI) of droplets. Here, we imaged freezing onsets, providing direct evidence of these proposed mechanisms. High-speed cryo-microscopy identified the onset location of freezing in droplets between two protein-repellent glass slides. INpro from sterilized P. syringae (Snomax) statistically favored nucleation at the AWI of the droplets. Removing cellular fragments by filtration or adding surfactants increased the frequency of nucleation events at the AWI. On the other hand, cultivated intact bacteria cells or lipid-free droplets nucleated ice without an affinity to the AWI. Overall, we provide visual evidence that INpro from P. syringae trigger freezing at hydrophobic interfaces, such as the AWI or the bacterial membrane, with important mechanistic implications for applications of INpro.

Evaluation of the regeneration process of the sciatic nerve of a mouse animal model after application of freezing, crushing or electrocoagulation damage / Ocena procesu regeneracji nerwu kulszowego mysiego modelu zwierzecego po zastosowaniu uszkodzenia metoda mrozenia, zmiazdzenia i elektrokoagulacji.

The problem of regeneration of damaged peripheral nerves is an ongoing topic and has long been the subject of intensive research worldwide. This study examined the morphological and functional evaluation of the regeneration process within the damaged sciatic nerve, a mouse animal model. The effect of impaired expression of the TSC-1 gene on the process of nerve regeneration was evaluated, depending on the mode of damage. The research object consisted of 48, 2-month-old male TSC lines. The test group consisted of animals that underwent damage to the sciatic nerve by crushing, freezing and electrocoagulation, while the control group includes mice whose sciatic nerve was not damaged. Behavioral tests were conducted to evaluate the functional return of the limb, after 3,5,7 and 14 days. The first changes in the regeneration process of the damaged neurite are observed as early as day 3 after the injury, while on day 14 after the injury the functional return of the damaged limb was noted.

A new strategy to improve the quality of frozen chicken wings: High voltage electrostatic field combined with phosphorus-free water retaining agent.

Freezing is a commonly used method for long-term storage of chicken wing products, of which disadvantages are mainly the product damage caused in the process. The aim of this study was to improve the freezing quality of chicken wings with a combination of phosphorus-free water retaining agent (WRA) and high-voltage electrostatic field (HVEF). The effect of WRA acting at different HVEF intensities (0, 1, 3, and 5 kV/cm) on the quality attributes of frozen chicken wings was investigated in 0, 7, 14, 21, 28 and 35 days of frozen storage. The results showed that WRA had functional properties of significantly improving the water holding capacity (WHC), color and texture properties, and fat stability of frozen chicken wing samples. The application of HVEF on this basis helped to promote the absorption of WRA and inhibit oxidative deterioration of chicken wing samples during frozen storage. Meanwhile, the combination of HVEF at 3 kV/cm was more prominent in terms of improvement in WHC, moisture content, color, protein secondary structure and microstructure integrity. This advantage had been consistently maintained with the extension of storage time. Overall, WRA combined with HVEF of 3 kV/cm can be used as an effective strategy to improve the freezing quality of chicken wing samples and has the potential to maintain the frozen chicken wing samples quality for a long time.

Thawed drip and its membrane-separated components: Role in retarding myofibrillar protein gel deterioration during freezing-thawing cycles.

Myofibrillar proteins are crucial for gel formation in processed meat products such as sausages and meat patties. Freeze-thaw cycles can alter protein properties, impacting gel stability and product quality. This study aims to investigate the potential of thawed drip and its membrane-separated components as potential antifreeze agents to retard denaturation, oxidation and gel deterioration of myofibrillar proteins during freezing-thawing cycles of pork patties. The thawed drip and its membrane-separated components of > 10 kDa and < 10 kDa, along with deionized water, were added to minced pork at 10 % mass fraction and subjected to increasing freeze-thaw cycles. Results showed that the addition of thawed drip and its membrane separation components inhibited denaturation and structural changes of myofibrillar proteins, evidenced by reduced surface hydrophobicity and carbonyl content, increased free sulfhydryl groups, protein solubility and α-helix, as compared to the deionized water group. Correspondingly, improved gel properties including water-holding capacity, textural parameters and denser network structure were observed with the addition of thawed drip and its membrane separation components. Denaturation and oxidation of myofibrillar proteins were positively correlated with gel deterioration during freezing-thawing cycles. We here propose a role of thawed drip and its membrane separation components as cryoprotectants against myofibrillar protein gel deterioration during freeze-thawing cycles.

Effects of multi-frequency ultrasound-assisted immersion freezing processing on myofibrillar protein structure and lipid oxidation of large yellow croaker (Larimichthys crocea) during long-time frozen storage.

In this study, large yellow croaker (Larimichthys crocea) was frozen using multi-frequency ultrasound-assisted freezing (MUIF) with different powers (160 W, 175 W, and 190 W, respectively) and stored at -18 °C for ten months. The effect of different ultrasound powers on the myofibrillar protein (MP) structures and lipid oxidation of large yellow croaker was investigated. The results showed that MUIF significantly slowed down the oxidation of MP by inhibiting carbonyl formation and maintaining high sulfhydryl contents. These treatments also held a high activity of Ca2+-ATPase in the MP. MUIF maintained a higher ratio of α-helix to ß-sheet during frozen storage, thereby protecting the secondary structure of the tissue and stabilizing the tertiary structure. In addition, MUIF inhibited the production of thiobarbituric acid reactive substances value and the loss of unsaturated fatty acid content, indicating that MUIF could better inhibit lipid oxidation of large yellow croaker during long-time frozen storage.

Optimizing Phycocyanin Extraction from Cyanobacterial Biomass: A Comparative Study of Freeze-Thaw Cycling with Various Solvents.

Cyanobacterial phycocyanin pigment is widely utilized for its properties in various industries, including food, cosmetics, and pharmaceuticals. Despite its potential, challenges exist, such as extraction methods impacting yield, stability, and purity. This study investigates the impact of the number of freeze-thaw (FT) cycles on the extraction of phycocyanin from the wet biomass of four cyanobacteria species (Arthrospira platensis, Chlorogloeopsis fritschii, Phormidium sp., and Synechocystis sp.), along with the impact of five extraction solutions (Tris-HCl buffer, phosphate buffer, CaCl2, deionized water, and tap water) at various pH values. Synechocystis sp. exhibited the highest phycocyanin content among the studied species. For A. platensis, Tris-HCl buffer yielded maximum phycocyanin concentration from the first FT cycle, while phosphate buffer provided satisfactory results from the second cycle. Similarly, Tris-HCl buffer showed promising results for C. fritschii (68.5% of the maximum from the first cycle), with the highest concentration (~12% w/w) achieved during the seventh cycle, using phosphate buffer. Phormidium sp. yielded the maximum pigment concentration from the first cycle using tap water. Among species-specific optimal extraction solutions, Tris-HCl buffer demonstrated sufficient extraction efficacy for all species, from the first cycle. This study represents an initial step toward establishing a universal extraction method for phycocyanin from diverse cyanobacteria species.

From freezing to functioning: cellular strategies of cold-adapted bacteria for surviving in extreme environments.

The ability of cold-adapted bacteria to survive in extreme cold and diverse temperatures is due to their unique attributes like cell membrane stability, up-regulation of peptidoglycan biosynthesis, increased production of extracellular polymeric substances, and expansion of membrane pigment. Various cold-adapted proteins, including ice-nucleating proteins (INPs), antifreeze proteins (AFPs), cold shock proteins (Csps), and cold-acclimated proteins (CAPs), help the bacteria to survive in these environments. To sustain cells from extreme cold conditions and maintain stability in temperature fluctuations, survival strategies at the molecular level and their mechanism play significant roles in adaptations in cryospheric conditions. Furthermore, cold shock domains present in the multifunctional cold shock proteins play crucial roles in their adaptation strategies. The considerable contribution of lipopeptides, osmolytes, and membrane pigments plays an integral part in their survival in extreme environments. This review summarizes the evolutionary history of cold-adapted bacteria and their molecular and cellular adaptation strategies to thrive in harsh cold environments. It also discusses the importance of carotenoids produced, lipid composition, cryoprotectants, proteins, and chaperones related to this adaptation. Furthermore, the functions and mechanisms of adaptations within the cell are discussed briefly. One can utilize and explore their potential in various biotechnology applications and their evolutionary journey by knowing the inherent mechanism of their molecular and cellular adaptation to cold climatic conditions. This review will help all branches of the life science community understand the basic microbiology of psychrophiles and their hidden prospect in life science research.

Frost fighters: unveiling the potential of microbial antifreeze proteins in biotech innovation.

Polar environments pose extreme challenges for life due to low temperatures, limited water, high radiation, and frozen landscapes. Despite these harsh conditions, numerous macro and microorganisms have developed adaptive strategies to reduce the detrimental effects of extreme cold. A primary survival tactic involves avoiding or tolerating intra and extracellular freezing. Many organisms achieve this by maintaining a supercooled state by producing small organic compounds like sugars, glycerol, and amino acids, or through increasing solute concentration. Another approach is the synthesis of ice-binding proteins, specifically antifreeze proteins (AFPs), which hinder ice crystal growth below the melting point. This adaptation is crucial for preventing intracellular ice formation, which could be lethal, and ensuring the presence of liquid water around cells. AFPs have independently evolved in different species, exhibiting distinct thermal hysteresis and ice structuring properties. Beyond their ecological role, AFPs have garnered significant attention in biotechnology for potential applications in the food, agriculture, and pharmaceutical industries. This review aims to offer a thorough insight into the activity and impacts of AFPs on water, examining their significance in cold-adapted organisms, and exploring the diversity of microbial AFPs. Using a meta-analysis from cultivation-based and cultivation-independent data, we evaluate the correlation between AFP-producing microorganisms and cold environments. We also explore small and large-scale biotechnological applications of AFPs, providing a perspective for future research.

Investigation of the protective effects of different forms of selenium in freezing dog semen: Comparison of nanoparticle selenium and sodium selenite.

This study aimed to investigate the protective effects of nanoparticle selenium (SeNP) and sodium selenite (SS) on preventing oxidative stress during the freezing process of dog semen. A total of six dogs were used in the study. The ejaculate was collected from dogs three times at different times by massage method. A total of 18 ejaculates were used and each ejaculate was divided in five experimental groups. The experimental groups were designed to tris extender containing no antioxidants control, 1 µg/mL SeNP1, 2 µg/mL SeNP2, and 1 µg/mL SS1 and 2 µg/mL SS2. Extended semen were equilibrated for 1 h at 4°C, then frozen in liquid nitrogen vapour and stored in liquid nitrogen (~-196°C). After thawing, semen samples were evaluated in terms of CASA motility and kinematic parameters, spermatozoa plasma membrane integrity and viability (HE Test), spermatozoa morphology (SpermBlue) and DNA fragmentation (GoldCyto). Antioxidant enzyme activity (glutathione peroxidase; GPX, superoxide dismutase; SOD, catalase; CAT) and lipid peroxidation (malondialdehyde; MDA) were evaluated in frozen-thawed dog sperm. When the results were evaluated statistically, the progressive motility, VCL, and VAP kinematic parameters in the SeNP1 group were significantly higher than the control group after thawing (p < .05). The highest ratio of plasma membrane integrity and viable spermatozoa was observed in the SeNP1 group, but there was no statistical difference found between the groups (p > .05). Although the ratio of total morphological abnormality was observed to be lower in all groups to which different selenium forms were added, compared to the control group, no statistical difference was found. Spermatozoa tail abnormality was significantly lower in the SeNP1 group than in the control and SS2 group (p < .05). The lowest ratio of fragmented DNA was observed in the SeNP1 group, but there was no statistical difference was found between the groups (p > .05). Although there was no statistical difference between the groups in the evaluation of sperm antioxidant profile, the highest GPX, SOD and CAT values and the lowest lipid peroxidation values were obtained in the SeNP1 group. As a result, it was determined that 1 µg/mL dose of SeNP added to the tris-based extender in dog semen was beneficial on spermatological parameters, especially sperm kinematic properties and sperm morphology, and therefore nanoparticle selenium, a nanotechnology product, made a significant contribution to the freezing of dog semen.

Maize residue retention shapes soil microbial communities and co-occurrence networks upon freeze-thawing cycles.

Maize residue retention is an effective agricultural practice for improving soil fertility in black soil region, where suffered from long freezing-thawing periods and intense freeze-thawing (FT) cycles. However, very few studies have examined the influence of maize residue retention on soil microbial communities under FT cycles. We investigated the response of soil microbial communities and co-occurrence networks to maize residue retention at different FT intensities over 12 cycles using a microcosm experiment conditioned in a temperature incubator. Our results indicated that maize residue retention induced dramatic shifts in soil archaeal, bacterial and fungal communities towards copiotroph-dominated communities. Maize residue retention consistently reduced soil fungal richness across all cycles, but this effect was weaker for archaea and bacteria. Normalized stochastic ratio analysis revealed that maize residue retention significantly enhanced the deterministic process of archaeal, bacterial and fungal communities. Although FT intensity significantly impacted soil respiration, it did not induce profound changes in soil microbial diversity and community composition. Co-occurrence network analysis revealed that maize residue retention simplified prokaryotic network, while did not impact fungal network complexity. The network robustness index suggested that maize residue retention enhanced the fungal network stability, but reduced prokaryotic network stability. Moreover, the fungal network in severe FT treatment harbored the most abundant keystone taxa, mainly being cold-adapted fungi. By identifying modules in networks, we observed that prokaryotic Module #1 and fungal Module #3 were enhanced by maize residue retention and contributed greatly to soil quality. Together, our results showed that maize residue retention exerted stronger influence on soil microbial communities and co-occurrence network patterns than FT intensity and highlighted the potential of microbial interactions in improving soil functionality.

Novel thawing method of ultrasound-assisted slightly basic electrolyzed water improves the processing quality of frozen shrimp compared with traditional thawing approaches.

Thawing is the primary step in handling frozen aquatic products, which directly determines their end-product quality. This study firstly constructed a novel thawing method of ultrasound-assisted slightly basic electrolyzed water (UST), and its influences on the physicochemical and histological properties of shrimp, as well as the structural of myofibrillar proteins (MPs) in shrimp were evaluated. Results indicated that the UST treatment greatly reduced 48.9 % thawing time of frozen shrimp compared to traditional thawing approaches. Meanwhile, the UST effectively decreased the generation of malondialdehyde (MDA), total volatile basic nitrogen (TVB-N), and carbonyl compounds in the thawed shrimps. In addition, it significantly preserved the elasticity and integrity of muscle fiber. Notably, the UST reduced the damage of thawing to the spatial structures of MPs, thereby greatly keeping the stability of protein. All these favorable changes maintained the water holding capacity (WHC) and quality of shrimp. Therefore, the UST is a promising non-thermal thawing technology for aquatic products.

Enhancing frozen dough quality: Investigating the impact of soy hull polysaccharide (SHP) on rheological properties and microstructure.

The effects of SHP on the texture, rheological properties, starch crystallinity and microstructure of frozen dough were investigated. The efficacy of SHP in enhancing dough quality is concentration-dependent, with frozen dough containing 1.5% SHP exhibiting hardness comparable to fresh dough without SHP (221.31 vs. 221.42 g). Even at 0.5% SHP, there is a noticeable improvement in frozen dough quality. The rheological results showed that the viscoelasticity of dough increased with higher SHP concentration. What's more, XRD and SEM results indicated that the SHP's hydrophilicity reduces the degree of starch hydrolysis, slows down the damage of starch particles during freezing, and consequently lowers the crystallinity of starch. Additionally, CLSM observations revealed that SHP enhances the gluten network structure, diminishing the appearance of holes. Therefore, the physical, chemical properties, and microstructure of frozen dough with SHP demonstrate significant enhancement, suggesting SHP's promising antifreeze properties and potential as a food antifreeze agent.

Habitat changes due to glacial freezing and melting reshape microbial networks.

The phenomenon of glacial freezing and thawing involves microbial sequestration, release, and colonization, which has the potential to impact ecosystem functioning through changes in microbial diversity and interactions. In this study, we examined the structural features of microbial communities of the Dongkemadi glacier, including bacteria, fungi, and archaea, in four distinct glacial environments (snow, ice, meltwater, and frontier soil). The sequestration, release, and colonization of glacial microbes have been found to significantly impact the diversity and structure of glacial microbial communities, as well as the complexity of microbial networks. Specifically, the complexity of bacterial networks has been observed to increase in a sequential manner during these processes. Utilizing the Inter-Domain Ecological Network approach, researchers have further explored the cross-trophic interactions among bacteria, fungi, and archaea. The complexity of the bacteria-fungi-archaea network exhibited a sequential increase due to the processes of sequestration, release, and colonization of glacial microbes. The release and colonization of glacial microbes led to a shift in the role of archaea as key species within the network. Additionally, our findings suggest that the hierarchical interactions among various microorganisms contributed to the heightened complexity of the bacteria-fungi-archaea network. The primary constituents of the glacial microbial ecosystem are unclassified species associated with the Polaromonas. It is noteworthy that various key species in glacial ecosystems are influenced by the distinct environmental factors. Moreover, our findings suggest that key species are not significantly depleted in response to abrupt alterations in individual environmental factors, shedding light on the dynamics of microbial cross-trophic interactions within glacial ecosystems.

Voltage recovery from frozen microbial fuel cells in the laboratory and outdoor field reactors.

Extreme temperature variations are a problem that must be faced in the practical application of microbial fuel cells (MFCs), but MFCs are not extensively described for low and even freezing temperatures. This study assessed the effect of low-temperature shock on the power generation performance and microbial community structure of MFCs. Two scales of MFCs, the small (mL-MFC) and the large (L-MFC), were constructed in the laboratory and their performance was evaluated before and after freezing at -18 °C. The experimental results demonstrate that both MFCs were capable of rapidly restoring their voltage to the previous level after thawing. For the mL-MFC (rGO/Ag), the power density recovered from 194.30 ± 10.84 mW/m2 to 195.57 ± 4.02 mW/m2 after thawing. For L-MFC (carbon felt electrodes), the power density increased significantly from the initial 1.79 mW/m2 to 173.90 mW/m2 after thawing, but the performance degradation problem after reactor amplification still needs to be solved. The sediment microbial fuel cell (SMFC) was successfully constructed and operated in a natural outdoor environment to maintain high voltage output after the period of frost. Microbial analysis indicated after the frost period, psychrotolerant microorganisms enriched on the anode, such as Flavobacterium and Psychrobacter, while the relative abundance of anaerobic methanogenic bacterium decreased. Overall, freeze-thaw operations had a non-negative impact on the performance of MFCs and provided some references for their practical applications.