Biosynthetic gene clusters with biotechnological applications in novel Antarctic isolates from Actinomycetota.

Actinomycetota have been widely described as valuable sources for the acquisition of secondary metabolites. Most microbial metabolites are produced via metabolic pathways encoded by biosynthetic gene clusters (BGCs). Although many secondary metabolites are not essential for the survival of bacteria, they play an important role in their adaptation and interactions within microbial communities. This is how bacteria isolated from extreme environments such as Antarctica could facilitate the discovery of new BGCs with biotechnological potential. This study aimed to isolate rare Actinomycetota strains from Antarctic soil and sediment samples and identify their metabolic potential based on genome mining and exploration of biosynthetic gene clusters. To this end, the strains were sequenced using Illumina and Oxford Nanopore Technologies platforms. The assemblies were annotated and subjected to phylogenetic analysis. Finally, the BGCs present in each genome were identified using the antiSMASH tool, and the biosynthetic diversity of the Micrococcaceae family was evaluated. Taxonomic annotation revealed that seven strains were new and two were previously reported in the NCBI database. Additionally, BGCs encoding type III polyketide synthases (T3PKS), beta-lactones, siderophores, and non-ribosomal peptide synthetases (NRPS) have been identified, among others. In addition, the sequence similarity network showed a predominant type of BGCs in the family Micrococcaceae, and some genera were distinctly grouped. The BGCs identified in the isolated strains could be associated with applications such as antimicrobials, anticancer agents, and plant growth promoters, among others, positioning them as excellent candidates for future biotechnological applications and innovations. KEY POINTS: • Novel Antarctic rare Actinomycetota strains were isolated from soil and sediments • Genome-based taxonomic affiliation revealed seven potentially novel species • Genome mining showed metabolic potential for novel natural products.

The Discovery of Weddellamycin, a Tricyclic Polyene Macrolactam Antibiotic from an Antarctic Deep-Sea-Derived Streptomyces sp. DSS69, by Heterologous Expression.

Polyene macrolactams are a special group of natural products with great diversity, unique structural features, and a wide range of biological activities. Herein, a cryptic gene cluster for the biosynthesis of putative macrolactams was disclosed from a sponge-associated bacterium, Streptomyces sp. DSS69, by genome mining. Cloning and heterologous expression of the whole biosynthetic gene cluster led to the discovery of weddellamycin, a polyene macrolactam bearing a 23/5/6 ring skeleton. A negative regulator, WdlO, and two positive regulators, WdlA and WdlB, involved in the regulation of weddellamycin production were unraveled. The fermentation titer of weddellamycin was significantly improved by overexpression of wdlA and wdlB and deletion of wdlO. Notably, weddellamycin showed remarkable antibacterial activity against various Gram-positive bacteria including MRSA, with MIC values of 0.10-0.83 µg/mL, and antifungal activity against Candida albicans, with an MIC value of 3.33 µg/mL. Weddellamycin also displayed cytotoxicity against several cancer cell lines, with IC50 values ranging from 2.07 to 11.50 µM.

Metabolomics approach for predicting stomach and colon contents in dead Arctocephalus pusillus pusillus, Arctocephalus tropicalis, Lobodon carcinophaga and Ommatophoca rossii from sub-Antarctic region.

The dietary habits of seals play a pivotal role in shaping management and administration policies, especially in regions with potential interactions with fisheries. Previous studies have utilized various methods, including traditional approaches, to predict seal diets by retrieving indigestible prey parts, such as calcified structures, from intestines, feces, and stomach contents. Additionally, methods evaluating nitrogen and stable isotopes of carbon have been employed. The metabolomics approach, capable of quantifying small-scale molecules in biofluids, holds promise for specifying dietary exposures and estimating disease risk. This study aimed to assess the diet composition of five seal species-Arctocephalus pusillus pusillus, Lobodon carcinophaga, Ommatophoca rossii, and Arctocephalus tropicalis 1 and 2-by analyzing stomach and colon contents collected from stranded dead seals at various locations. Metabolite concentrations in the seal stomach and colon contents were determined using Nuclear Magnetic Resonance Spectroscopy. Among the colon and stomach contents, 29 known and 8 unknown metabolites were identified. Four metabolites (alanine, fumarate, lactate, and proline) from stomach contents and one metabolite (alanine) from colon contents showed no significant differences between seal species (p>0.05). This suggests that traces of these metabolites in the stomach and colon contents may be produced by the seals' gut microbiome or derived from other animals, possibly indicating reliance on fish caught at sea. Despite this insight, the cause of death for stranded seals remains unclear. The study highlights the need for specific and reliable biomarkers to precisely indicate dietary exposures across seal populations. Additionally, there is a call for the development of relevant metabolite and disease interaction networks to explore disease-related metabolites in seals. Ultimately, the metabolomic method employed in this study reveals potential metabolites in the stomach and colon contents of these seal species.

Geographical distribution of close kin in southern right whales on feeding grounds.

This study investigated the close kinship structure of southern right whales on feeding grounds during austral summer seasons. The study was based on biopsy samples of 171 individual whales, which were genotyped with 14 microsatellite DNA loci. Kinship was investigated by using the LOD (Log Odds) score, a relatedness index for a pair of genotypes. Based on a cut-off point of LODPO > 6, which was chosen to balance false positives and negatives, a total of 28 dyads were inferred. Among these, 25 were classified as parent-offspring pairs. Additional genetic (mitochondrial DNA haplotypes) and biological (estimated body length, sex) data were used to provide additional information on the inferred close kin pairs. The elapsed time between sampling varied from 0 (close kin detected in the same austral summer season) to 17 years. All the kin pairs occurred within the Antarctic Indo sector (85°-135°E) and no pair occurred between whales within and outside of this sector. Six pairs were between individuals in high (Antarctic) and lower latitudes. Results of the present analysis on kinship are consistent with the views that whales in the Indo sector of the Antarctic are related with the breeding ground in Southwest Australia, and that whales from this population can occupy different feeding grounds. The present study has the potential to contribute to the conservation of the southern right whales through the monitoring of important population parameters such as population sizes and growth rate, in addition to assist the interpretation of stock structure derived from standard population genetic analyses.

Diverse papillomaviruses identified from Antarctic fur seals, leopard seals and Weddell seals from the Antarctic.

Papillomaviruses (family Papillomaviridae) are non-enveloped, circular, double-stranded DNA viruses known to infect squamous and mucosal epithelial cells. In the family Papillomaviridae there are 53 genera and 133 viral species whose members infect a variety of mammalian, avian, reptilian, and fish species. Within the Antarctic context, papillomaviruses (PVs) have been identified in Adélie penguins (Pygoscelis adeliae, 2 PVs), Weddell seals (Leptonychotes weddellii, 7 PVs), and emerald notothen (Trematomus bernacchii, 1 PV) in McMurdo Sound and Ross Island in eastern Antarctica. Here we identified 13 diverse PVs from buccal swabs of Antarctic fur seals (Arctocephalus gazella, 2 PVs) and leopard seal (Hydrurga leptonyx, 3 PVs) in western Antarctica (Antarctic Peninsula), and vaginal and nasal swabs of Weddell seals (8 PVs) in McMurdo Sound. These PV genomes group into four genera representing 11 new papillomavirus types, of which five are from two Antarctic fur seals and a leopard seal and six from Weddell seals.

Antarctic marine sediment as a source of filamentous fungi-derived antimicrobial and antitumor compounds of pharmaceutical interest.

Antarctica harbors a microbial diversity still poorly explored and of inestimable biotechnological value. Cold-adapted microorganisms can produce a diverse range of metabolites stable at low temperatures, making these compounds industrially interesting for biotechnological use. The present work investigated the biotechnological potential for antimicrobial and antitumor activity of filamentous fungi and bacteria isolated from marine sediment samples collected at Deception Island, Antarctica. A total of 89 microbial isolates were recovered from marine sediments and submitted to an initial screening for L-glutaminase with antitumoral activity and for antimicrobial metabolites. The isolates Pseudogymnoascus sp. FDG01, Pseudogymnoascus sp. FDG02, and Penicillium sp. FAD33 showed potential antiproliferative action against human pancreatic carcinoma cells while showing no toxic effect on non-tumor cells. The microbial extracts from unidentified three bacteria and four filamentous fungi showed antibacterial activity against at least one tested pathogenic bacterial strain. The isolate FDG01 inhibited four bacterial species, while the isolate FDG01 was active against Micrococcus luteus in the minimal inhibitory concentration of 0.015625 µg mL -1. The results pave the way for further optimization of enzyme production and characterization of enzymes and metabolites found and reaffirm Antarctic marine environments as a wealthy source of compounds potentially applicable in the healthcare and pharmaceutical industry.

Detection of plastic, cellulosic micro-fragments and microfibers in Laternula elliptica from King George Island (Maritime Antarctica).

It is generally acknowledged that microplastic pollutants are prevalent in ocean waters and sediments across a range of tropical, temperate, subpolar, and polar regions. The waters surrounding King George Island are significantly impacted by human activities, particularly those related to scientific stations, fishing, and tourism. Organisms, such as Laternula elliptica, can be used as environmental monitors due to the likelihood that they will bioaccumulate pollutants. The goal of this study was to quantify and identify plastic and cellulosic micro-fragments and microfibers present in the soft body of clams (n = 21), collected from Fildes Bay near sewage and wastewater discharges. Plastic and cellulose microfragments and microfibers were counted, and their compositions were determined using FT-IR. All 21 individuals sampled contained fragments and fibers, with a total of 900 items detected (42.86 ± 25.36 mean ± SD items per individual), or 1.82 items g.wet mass-1. 58 % of items were cellulose and 22 % plastic. Considering the plastic polymer compositions, 28.57 % were polyethylene terephthalate (PET), 21.43 % acrylic, 14.29 % high-density polyethylene (HDPE), 14.29 % Polypropylene (PP), 7.14 % ultra-high drawn polyethylene filament (UHMWPE), 7.14 % polyester and 7.14 % Polyethylene. The quantities and prevalence of MP in L. elliptica were higher than those found in other Antarctic marine species, and even in bivalves from populated regions of the world. Our work assessed the pollution status of L. elliptica near an effluent of wastewater plants and found that 95 % of individuals displayed MP and 100 % microfibers that could impact their population.

Extraction, identification, and molecular mechanisms of α-glucosidase inhibitory peptides from defatted Antarctic krill (Euphausia superba) powder hydrolysates.

The objective of this study was to explore the potential of Antarctic krill-derived peptides as α-glucosidase inhibitors for the treatment of type 2 diabetes. The enzymolysis conditions of α-glucosidase inhibitory peptides were optimized by response surface methodology (RSM), a statistical method that efficiently determines optimal conditions with a limited number of experiments. Gel chromatography and LC-MS/MS techniques were utilized to determine the molecular weight (Mw) distribution and sequences of the hydrolysates. The identification and analysis of the mechanism behind α-glucosidase inhibitory peptides were conducted through conventional and computer-assisted techniques. The binding affinities between peptides and α-glucosidase were further validated using BLI (biolayer interferometry) assay. The results revealed that hydrolysates generated by neutrase exhibited the highest α-glucosidase inhibition rate. Optimal conditions for hydrolysis were determined to be an enzyme concentration of 6 × 103 U/g, hydrolysis time of 5.4 h, and hydrolysis temperature of 45 °C. Four peptides (LPFQR, PSFD, PSFDF, VPFPR) with strong binding affinities to the active site of α-glucosidase, primarily through hydrogen bonding and hydrophobic interactions. This study highlights the prospective utility of Antarctic krill-derived peptides in curtailing α-glucosidase activity, offering a theoretical foundation for the development of novel α-glucosidase inhibitors and related functional foods to enhance diabetes management.

Anthropogenic debris in three sympatric seal species of the Western Antarctic Peninsula.

Litter pollution is a growing concern, including for Antarctica and the species that inhabit this ecosystem. In this study, we investigated the microplastic contamination in three seal species that inhabit the Western Antarctic Peninsula: crabeater (Lobodon carcinophaga), leopard (Hydrurga leptonyx) and Weddell (Leptonychotes weddellii) seals. Given the worldwide ubiquity of this type of contaminant, including the Southern Ocean, we hypothesized that the three seal species would present anthropogenic debris in their feces. We examined 29 scat samples of crabeater (n = 5), leopard (n = 13) and Weddell (n = 11) seals. The chemical composition of the items found were identified using micro-Raman and micro-FTIR spectroscopies. All the samples of the three species presented anthropic particles (frequency of occurrence - %FO - 100 %). Fibers were the predominant debris, but fragments and filaments were also present. Particles smaller than 5 mm (micro debris) were predominant in all the samples. Leopard seals ingested significantly larger micro-debris in comparison with the other seal species. The dominant color was black followed by blue and white. Micro-Raman and micro-FTIR Spectroscopies revealed the presence of different anthropogenic pigments such as reactive blue 238, Indigo 3600 and copper phthalocyanine (blue and green). Carbon black was also detected in the samples, as well as plastic polymers such as polystyrene, polyester and polyethylene terephthalate (PET), polyamide, polypropylene and polyurethane These results confirm the presence of anthropogenic contamination in Antarctic seals and highlight the need for actions to mitigate the effects and reduce the contribution of debris in the Antarctic ecosystem.

Diversified Chemical Structures and Bioactivities of the Chemical Constituents Found in the Brown Algae Family Sargassaceae.

Sargassaceae, the most abundant family in Fucales, was recently formed through the merging of the two former families Sargassaceae and Cystoseiraceae. It is widely distributed in the world's oceans, notably in tropical coastal regions, with the exception of the coasts of Antarctica and South America. Numerous bioactivities have been discovered through investigations of the chemical diversity of the Sargassaceae family. The secondary metabolites with unique structures found in this family have been classified as terpenoids, phlorotannins, and steroids, among others. These compounds have exhibited potent pharmacological activities. This review describes the new discovered compounds from Sargassaceae species and their associated bioactivities, citing 136 references covering from March 1975 to August 2023.

Synthesis of Bioactive Nickel Nanoparticles Using Bacterial Strains from an Antarctic Consortium.

Marine microorganisms have been demonstrated to be an important source for bioactive molecules. In this paper we report the synthesis of Ni nanoparticles (NiSNPs) used as reducing and capping agents for five bacterial strains isolated from an Antarctic marine consortium: Marinomonas sp. ef1, Rhodococcus sp. ef1, Pseudomonas sp. ef1, Brevundimonas sp. ef1, and Bacillus sp. ef1. The NiSNPs were characterized by Ultraviolet-visible (UV-vis) spectroscopy, Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopic analysis. The maximum absorbances in the UV-Vis spectra were in the range of 374 nm to 422 nm, corresponding to the Surface plasmon resonance (SPR) of Nickel. DLS revealed NiSNPs with sizes between 40 and 45 nm. All NiSNPs were polycrystalline with a face-centered cubic lattice, as revealed by XRD analyses. The NiSNPs zeta potential values were highly negative. TEM analysis showed that the NiSNPs were either spherical or rod shaped, well segregated, and with a size between 20 and 50 nm. The FTIR spectra revealed peaks of amino acid and protein binding to the NiSNPs. Finally, all the NiSNPs possess significant antimicrobial activity, which may play an important role in the management of infectious diseases affecting human health.

Dietary antarctic krill improves antioxidant capacity, immunity and reduces lipid accumulation, insights from physiological and transcriptomic analysis of Plectropomus leopardus.

BACKGROUND: Due to its enormous biomass, Antarctic krill (Euphausia superba) plays a crucial role in the Antarctic Ocean ecosystem. In recent years, Antarctic krill has found extensive application in aquaculture, emerging as a sustainable source of aquafeed with ideal nutritional profiles. However, a comprehensive study focused on the detailed effects of dietary Antarctic krill on aquaculture animals, especially farmed marine fishes, is yet to be demonstrated. RESULTS: In this study, a comparative experiment was performed using juvenile P. leopardus, fed with diets supplemented with Antarctic krill (the krill group) or without Antarctic krill (the control group). Histological observation revealed that dietary Antarctic krill could reduce lipid accumulation in the liver while the intestine exhibited no obvious changes. Enzyme activity measurements demonstrated that dietary Antarctic krill had an inhibitory effect on oxidative stress in both the intestine and the liver. By comparative transcriptome analysis, a total of 1,597 and 1,161 differentially expressed genes (DEGs) were identified in the intestine and liver, respectively. Functional analysis of the DEGs showed multiple enriched terms significantly related to cholesterol metabolism, antioxidants, and immunity. Furthermore, the expression profiles of representative DEGs, such as dhcr7, apoa4, sc5d, and scarf1, were validated by qRT-PCR and fluorescence in situ hybridization. Finally, a comparative transcriptome analysis was performed to demonstrate the biased effects of dietary Antarctic krill and astaxanthin on the liver of P. leopardus. CONCLUSIONS: Our study demonstrated that dietary Antarctic krill could reduce lipid accumulation in the liver of P. leopardus, enhance antioxidant capacities in both the intestine and liver, and exhibit molecular-level improvements in lipid metabolism, immunity, and antioxidants. It will contribute to understanding the protective effects of Antarctic krill in P. leopardus and provide insights into aquaculture nutritional strategies.

Characterization of halogen species in seaweeds from the Antarctic using a multi-technique approach.

BACKGROUND: Despite the recognized importance, the determination of halogens in Antarctic seaweeds remains understudied. Limited research exists due to challenges associated with sample preparation, and reliable analytical techniques for this type of analysis. Therefore, further investigations are necessary to bridge this knowledge gap and gain a comprehensive understanding of halogen metabolism in Antarctic seaweeds. METHODS: In this study, seaweeds from the coast of the Antarctic continent were characterized concerning the total content of halogens and their species. For this purpose, different sample preparation methods, based on extraction and combustion, combining highly selective and sensitive chromatographic and spectrometric multi-technique approaches were used. RESULTS: By using optimized methods, it was possible to determine total halogens content, the distribution of bromine and iodine in different classes of species (lipids, water-soluble, proteins, carbohydrates, and residue), as well as the identification of iodinated amino acids (MIT and DIT) in ten brown and red seaweeds. Bromate and iodate were not detected in the samples, which presented only bromide and iodide species in their composition. Additionally, unknown bromine and iodine species were observed in different extracts evaluated. Furthermore, 25 halogenated polyphenols were identified in seaweeds, of which only four were already reported in the literature. CONCLUSION: The results obtained in this study comprise unprecedented data in the literature on species of halogens present in seaweeds from the Antarctic environment.

Implementation of simple and effective fine droplet formation-based spray-assisted liquid phase microextraction for the simultaneous determination of twenty-nine endocrine disruptor compounds and pesticides in rock, soil, water, moss, and feces samples from antarctica using gas chromatography-mass spectrometry.

This study established the simultaneous determination of the selected endocrine-disrupting compounds (EDCs) and pesticides in rock, soil, water, moss, and feces samples collected from the Antarctic region. The spray-assisted droplet formation-based liquid phase microextraction (SADF-LPME) coupled to GC-MS system was developed and validated for the screening and monitoring of 29 selected EDCs and pesticides. Binary solvent system, 1:1 (v/v) dichlormethane: 1,2-dichloroethane mixture was employed as an extraction solvent and sprayed onto sample or standard solutions using a straightforward and practical spray apparatus. The factors affecting the extraction process such as extraction solvent type and ratio, extraction solvent volume (spray repetition), vortexing period, and sample pH were properly optimized. Analytical figures of the merit of the method were recorded under the optimal extraction/chromatographic conditions. The LOD, LOQ, and enhancement factor were in the range of 1.0 to 6.6 ng/g, 3.2 to 22.1 ng/g, and 3.7 to 158.9, respectively. The method demonstrated a good linear working range for all the selected analytes with proper coefficients of determination. The usability and reliability of the microextraction strategy was confirmed using seawater, moss, and soil samples, and the %recoveries were within an acceptable range (> 70%) for all examined samples. The environmental samples collected from the Horseshoe and Faure Islands of the Antarctica region were analyzed to assess the potential pollution of EDCs and pesticides. This method has the potential to be employed for the analysis of EDCs in routine analytical laboratories and for controlling and screening the organic pollutant content of different environmental samples.

Pseudomonas violetae sp. nov. and Pseudomonas emilianonis sp. nov., two new species with the ability to degrade TNT isolated from soil samples at Deception Island, maritime Antarctica.

Two motile, rod-shaped, Gram-stain-negative bacterial strains, TNT11T and TNT19T, were isolated from soil samples collected at Deception Island, Antarctica. According to the 16S rRNA gene sequence similarity, both strains belong to the genus Pseudomonas. Further genomic analyses based on ANI and dDDH suggested that these strains were new species. Growth of strain TNT11T is observed at 0-30 â„ƒ (optimum, 20 â„ƒ), pH 4.0-9.0 (optimum, pH 6.0) and in the presence of 0-5.0% NaCl (optimum, 1% NaCl), while for TNT19T is observed at 0-30 â„ƒ (optimum between 15 and 20 â„ƒ), pH 5.0-9.0 (optimum, pH 6.0) and in the presence of 0-5.0% NaCl (optimum between 0 and 1% NaCl). The fatty acid profile consists of the major compounds; C16:0 and C16:1 ω6 for TNT11T, and C16:0 and C12:0 for TNT19T. Based on the draft genome sequences, the DNA G + C content for TNT11T is 60.43 mol% and 58.60 mol% for TNT19T. Based on this polyphasic study, TNT11T and TNT19T represent two novel species of the genus Pseudomonas, for which the proposed names are Pseudomonas violetae sp. nov. and Pseudomonas emilianonis sp. nov., respectively. The type strains are Pseudomonas violetae TNT11T (= RGM 3443T = LMG 32959T) and Pseudomonas emilianonis TNT19T (= RGM 3442T = LMG 32960T). Strains TNT11T and TNT19T were deposited to CChRGM and BCCM/LMG with entry numbers RGM 3443/LMG 32959 and RGM 3442/LMG 32960, respectively.

Novel Ca-Chelating Peptides from Protein Hydrolysate of Antarctic Krill (Euphausia superba): Preparation, Characterization, and Calcium Absorption Efficiency in Caco-2 Cell Monolayer Model.

Antarctic krill (Euphausia superba) is the world's largest resource of animal proteins and is thought to be a high-quality resource for future marine healthy foods and functional products. Therefore, Antarctic krill was degreased and separately hydrolyzed using flavourzyme, pepsin, papain, and alcalase. Protein hydrolysate (AKH) of Antarctic krill prepared by trypsin showed the highest Ca-chelating rate under the optimized chelating conditions: a pH of 8.0, reaction time of 50 min, temperature of 50 °C, and material/calcium ratio of 1:15. Subsequently, fourteen Ca-chelating peptides were isolated from APK by ultrafiltration and a series of chromatographic methods and identified as AK, EAR, AEA, VERG, VAS, GPK, SP, GPKG, APRGH, GVPG, LEPGP, LEKGA, FPPGR, and GEPG with molecular weights of 217.27, 374.40, 289.29, 459.50, 275.30, 300.36, 202.21, 357.41, 536.59, 328.37, 511.58, 516.60, 572.66, and 358.35 Da, respectively. Among fourteen Ca-chelating peptides, VERG presented the highest Ca-chelating ability. Ultraviolet spectrum (UV), Fourier Transform Infrared (FTIR), and scanning electron microscope (SEM) analysis indicated that the VERG-Ca chelate had a dense granular structure because the N-H, C=O and -COOH groups of VERG combined with Ca2+. Moreover, the VERG-Ca chelate is stable in gastrointestinal digestion and can significantly improve Ca transport in Caco-2 cell monolayer experiments, but phytate could significantly reduce the absorption of Ca derived from the VERG-Ca chelate. Therefore, Ca-chelating peptides from protein hydrolysate of Antarctic krill possess the potential to serve as a Ca supplement in developing healthy foods.

Screening of endophytic fungi from Antarctic mosses: Potential production for L-asparaginase free of glutaminase and urease activity.

Studies involving endophytic fungi aim to identify organisms inhabiting extreme and relatively unexplored environments, as these fungi possess unique characteristics and uncommon biochemical pathways that enable them to produce compounds with biotechnological potential. Among various enzymes, L-Asparaginase is employed in the treatment of Acute Lymphoblastic Leukemia. In this study, we identified endophytic fungi from Sanionia uncinata and Polytrichastrum alpinum collected on King George Island in Antarctica. The fungi were categorized into morphological groups based on their characteristics, molecularly identified, and assessed for L-Asparaginase (L-ASNase) enzyme production. Subsequently, production optimization was conducted. A total of 161 endophytes were isolated from 504 moss gametophytes, with 107 originating from P. alpinum and 54 from S. uncinata. These isolates were categorized into 31 morphotypes. Fungi exhibiting high enzyme production were identified molecularly. Among them, nine identified isolates belonged to the genera Aspergillus, Collariella, Diaporthe, Epicoccum, Peroneutypa, Xylaria, and Trametes. Three of these isolates were identified at the species level through multigene phylogeny, namely Epicoccum nigrum, Collariella virescens, and Peroneutypa scoparia. All 31 fungi were subjected to solid media testing for L-ASNase enzyme production, with 22 isolates demonstrating production capability, and 13 of them produced L-ASNase free from Urease and Glutaminase. The isolates displaying solid media production underwent further testing in liquid media, all of which exhibited enzyme production ranging from 0.75 to 1.29 U g-1. Notably, the three fungi identified at the species level were the highest producers of the enzyme (1.29, 1.17, and 1.13 U g-1). The production of these fungi was optimized using the Taguchi method, resulting in production values ranging from 0.687 to 2.461 U g-1. In conclusion, our findings indicate that Antarctic moss endophytic fungi exhibit significant potential for the production of the anti-leukemic enzyme L-ASNase.

Molecular determinants for cold adaptation in an Antarctic Na+/K+-ATPase.

Enzymes from ectotherms living in chronically cold environments have evolved structural innovations to overcome the effects of temperature on catalysis. Cold adaptation of soluble enzymes is driven by changes within their primary structure or the aqueous milieu. For membrane-embedded enzymes, like the Na+/K+-ATPase, the situation is different because changes to the lipid bilayer in which they operate may also be relevant. Although much attention has been focused on thermal adaptation within lipid bilayers, relatively little is known about the contribution of structural changes within membrane-bound enzymes themselves. The identification of specific mutations that confer temperature compensation is complicated by the presence of neutral mutations, which can be more numerous. In the present study, we identified specific amino acids in a Na+/K+-ATPase from an Antarctic octopus that underlie cold resistance. Our approach was to generate chimeras between an Antarctic clone and a temperate ortholog and then study their temperature sensitivities in Xenopus oocytes using an electrophysiological approach. We identified 12 positions in the Antarctic Na+/K+-ATPase that, when transferred to the temperate ortholog, were sufficient to confer cold tolerance. Furthermore, although all 12 Antarctic mutations were required for the full phenotype, a single leucine in the third transmembrane segment (M3) imparted most of it. Mutations that confer cold resistance are mostly in transmembrane segments, at positions that face the lipid bilayer. We propose that the interface between a transmembrane enzyme and the lipid bilayer is a critical determinant of temperature sensitivity and, accordingly, has been a prime evolutionary target for thermal adaptation.

Protective Effect of Mycosporine-like Amino Acids Isolated from an Antarctic Diatom on UVB-Induced Skin Damage.

Although it is well recognized that mycosporine-like amino acids (MAAs) are ultraviolet (UV) protective agents that can reduce UV damage, the specific biological mechanism of its role in the skin remains unclear. In this study, we investigated the effect of MAAs extracted from Antarctic diatom Phaeodactylum tricornutum ICE-H on UVB-induced skin damage using a mice model. The MAAs components identified by liquid chromatography-tandem mass spectrometry included 4-deoxygadusol, shinorine, and porphyra-334, which were purified using a Supledean Carboxen1000 solid phase extraction column. The antioxidant activities of these MAA compounds were tested in vitro. For UVB-induced skin photodamage in mice, MAAs alleviated skin swelling and epidermal thickening in this study. We detected the content of reactive oxygen species (ROS), malondialdehyde, and collagen in skin tissue. In addition, quantitative real-time polymerase chain reaction was used to detect nuclear factor-κB (NF-κB), tumor necrosis factor α, interleukin-1ß, cyclooxygenase-2, mitogen activated protein kinase (MAPK) family (extracellular signal-regulated kinase, c-Jun amino-terminal kinase, and p38 kinase), and matrix metalloproteinases. The expression of these cytokines and enzymes is related to inflammatory responses and collagen degradation. In comparison to the model group without MAA treatment, the MAA component decreased the concentration of ROS, the degree of oxidative stress in the skin tissue, and the expression of genes involved in the NF-κB and MAPK pathways. In summary, these MAA components extracted from Phaeodactylum tricornutum ICE-H protected against UVB-induced skin damage by inhibiting ROS generation, relieving skin inflammation, and slowing down collagen degradation, suggesting that these MAA components are effective cosmetic candidate molecules for the protection and therapy of UVB damage.

Cold-Driven Hemoglobin Evolution in Antarctic Notothenioid Fishes Prior to Hemoglobin Gene Loss in White-Blooded Icefishes.

Expression of multiple hemoglobin isoforms with differing physiochemical properties likely helps species adapt to different environmental and physiological conditions. Antarctic notothenioid fishes inhabit the icy Southern Ocean and display fewer hemoglobin isoforms, each with less affinity for oxygen than temperate relatives. Reduced hemoglobin multiplicity was proposed to result from relaxed selective pressure in the cold, thermally stable, and highly oxygenated Antarctic waters. These conditions also permitted the survival and diversification of white-blooded icefishes, the only vertebrates living without hemoglobin. To understand hemoglobin evolution during adaptation to freezing water, we analyzed hemoglobin genes from 36 notothenioid genome assemblies. Results showed that adaptation to frigid conditions shaped hemoglobin gene evolution by episodic diversifying selection concomitant with cold adaptation and by pervasive evolution in Antarctic notothenioids compared to temperate relatives, likely a continuing adaptation to Antarctic conditions. Analysis of hemoglobin gene expression in adult hematopoietic organs in various temperate and Antarctic species further revealed a switch in hemoglobin gene expression underlying hemoglobin multiplicity reduction in Antarctic fish, leading to a single hemoglobin isoform in adult plunderfishes and dragonfishes, the sister groups to icefishes. The predicted high hemoglobin multiplicity in Antarctic fish embryos based on transcriptomic data, however, raises questions about the molecular bases and physiological implications of diverse hemoglobin isoforms in embryos compared to adults. This analysis supports the hypothesis that the last common icefish ancestor was vulnerable to detrimental mutations affecting the single ancestral expressed alpha- and beta-globin gene pair, potentially predisposing their subsequent loss.