Pseudoalteromonas Species Research Articles

Genome-based taxonomic analysis of the genus Pseudoalteromonas reveals heterotypic synonyms.

The Pseudoalteromonas genus comprises members that have been demonstrated to play significant ecological roles and produce enzymes, natural products, and activities that are beneficial to the environment and economy. A comprehensive evaluation of the genus revealed that the genomes of several Pseudoalteromonas species are highly similar to each other, exceeding species cutoff values. This evaluation involved determining and comparing the average nucleotide identity, in silico DNA-DNA hybridization, average amino acid identity, and the difference in G + C% between Pseudoalteromonas type strains with publicly available genomes. The genome of the Pseudoalteromonas elyakovii type strain was further assessed through additional sequencing and genomic comparisons to historical sequences. These findings suggest that six Pseudoalteromonas species, namely P. mariniglutinosa, P. donghaensis, P. maricaloris, P. elyakovii, P. profundi, and P. issachenkonii, should be reclassified as later heterotypic synonyms of the following validly published species: P. haloplanktis, P. lipolytica, P. flavipulchra, P. distincta, P. gelatinilytica, and P. tetraodonis. Furthermore, two names without valid standing, 'P. telluritireducens' and 'P. spiralis', should be associated with the validly published Pseudoalteromonas species P. agarivorans and P. tetraodonis, respectively.

Genomic Analysis of Two Cold-Active Pseudoalteromonas Phages Isolated from the Continental Shelf in the Arctic Ocean.

Cold-active bacteriophages are bacterial viruses that infect and replicate at low temperatures (≤4 °C). Understanding remains limited of how cold-active phage-host systems sustain high viral abundance despite the persistently low temperatures in pelagic sediments in polar seas. In this study, two Pseudoalteromonas phages, ACA1 and ACA2, were isolated from sediment core samples of the continental shelf in the western Arctic Ocean. These phages exhibited successful propagation at a low temperature of 1 °C and displayed typical myovirus morphology with isometric icosahedral heads and contractile tails. The complete genome sequences of phages ACA1 and ACA2 were 36,825 bp and 36,826 bp in size, respectively, sharing almost the same gene content. These are temperate phages encoding lysogeny-related proteins such as anti-repressor, immunity repressor and integrase. The absence of cross-infection between the host strains, which were genomically distinct Pseudoalteromonas species, can likely be attributed to heavy divergence in the anti-receptor apparently mediated by an associated diversity-generating retroelement. HHpred searching identified genes for all of the structural components of a P2-like phage (family Peduoviridae), although the whole of the Peduoviridae family appeared to be divided between two anciently diverged tail modules. In contrast, Blast matching and whole genome tree analysis are dominated by a nonstructural gene module sharing high similarity with Pseudoalteromonas phage C5a (founder of genus Catalunyavirus). This study expands the knowledge of diversity of P2-like phages known to inhabit Peudoalteromonas and demonstrates their presence in the Arctic niche.

Use of marine microorganisms in designing anti-infective strategies for sustainable aquaculture production.

Aquaculture, a noteworthy food production sector, is confronted with disease occurrences. Treatment of aquaculture pathogens with antibiotics is often rendered ineffective due to biofilm formation and the development of resistant strains. Marine ecosystems encompass unusual microorganisms that produce novel bioactive compounds, including agents that could be used as alternatives to antibiotics. Moreover, biomass and/or biomolecules associated with these microorganisms could act as feed supplements to enhance overall health of aquaculture species' and improve water quality parameters. The present review summarizes contents of studies on such marine microorganisms with the potential to be developed as agents for tackling bacterial diseases in the aquaculture segment. Bioactive compounds produced by marine bacteria are known to inhibit biofilm associated infections mediated by their bactericidal properties (produced by Bacillus, Vibrio, Photobacterium and Pseudoalteromonas species), surfactant activity (obtained from different species of Bacillus and Staphylococcus lentus), anti-adhesive activity (derived from Bacillus sp. and Brevibacterium sp.) and quorum sensing inhibition. Several marine fungal isolates capable of producing antibacterial agents have also been effective in inhibiting aquaculture associated pathogens. Another strategy followed by investigators to reduce severity of infections is the use of bacterial, yeast and microalgae biomass as feed supplements, probiotics and immunostimulants. In some cases, marine microalgae have been employed as sustainable alternatives to fish oil and fish meal without compromising on nutritional quality. Their inclusion in aquaculture feed have enhanced growth, favoured better survival of cultured species and improved water quality parameters. Marine microorganisms (by providing effective bioactive compounds and being used as feed supplements) could enable aquaculture practices to be more sustainable in the future.

Complete Genomic Sequence of an Agarolytic Pseudoalteromonas Species Isolated from Deep Seawater.

We report the complete genomic sequence of the agarolytic bacterium Pseudoalteromonas sp. strain MM1, recovered from deep seawater. The genome has two circular chromosomes with sizes of 3,686,652 bp and 802,570 bp and GC contents of 40.8 and 40.0%, and it carries 3,967 protein-coding sequences, 24 rRNA genes, and 103 tRNA genes.

Bioprospecting for Novel Bacterial Sources of Hydrolytic Enzymes and Antimicrobials in the Romanian Littoral Zone of the Black Sea.

Marine microorganisms have evolved a large variety of metabolites and biochemical processes, providing great opportunities for biotechnologies. In the search for new hydrolytic enzymes and antimicrobial compounds with enhanced characteristics, the current study explored the diversity of cultured and uncultured marine bacteria in Black Sea water from two locations along the Romanian coastline. Microbial cell density in the investigated samples varied between 65 and 12.7 × 103 CFU·mL-1. The total bacterial community identified by Illumina sequencing of 16S rRNA gene comprised 185 genera belonging to 46 classes, mainly Gammaproteobacteria, Alphaproteobacteria, Flavobacteriia, and 24 phyla. The 66 bacterial strains isolated on seawater-based culture media belonged to 33 genera and showed variable growth temperatures, growth rates, and salt tolerance. A great fraction of these strains, including Pseudoalteromonas and Flavobacterium species, produced extracellular proteases, lipases, and carbohydrases, while two strains belonging to the genera Aquimarina and Streptomyces exhibited antimicrobial activity against human pathogenic bacteria. This study led to a broader view on the diversity of microbial communities in the Black Sea, and provided new marine strains with hydrolytic and antimicrobial capabilities that may be exploited in industrial and pharmaceutical applications.

Inhibitory relationships of resident bacteria isolated from the mantle fluids of Crassostrea virginica.

Thirteen aerobic, halotolerant marine bacterial strains were isolated from the mantle fluids and associated mucus of the eastern oyster Crassostrea virginica harvested from the highly impacted Black Rock Harbor in western Long Island Sound. All isolated strains were Gram negative and had previously been identified using 16S RNA gene sequence analysis. These 13 strains were examined for their ability to inhibit the growth of each other employing a diffusion agar method used by antibiotic assays. All challenger strains were able to inhibit at least one of the indicator isolates. Enhanced antimicrobial activity was observed from cultures of Pseudoalteromonas sp. (L), Shewanella sp. (H), Thalassospira sp. (JA), and Alteromonas sp. (JB) when used to challenge the indicator isolates. The indicator isolate most sensitive to antimicrobial activity was another Pseudoalteromonas species (KC) whose growth was inhibited by 10 of the challenger strains, whereas Pseudoalteromonas (L) was resistant to all growth challenges. Growth autoinhibition was observed with isolates Tenacibaculum ascidiaceicola (KC), Vibrio (B), and Shewanella (H) during a 24 h incubation. No antimicrobial growth inhibition was detected when 24 and 48 h cell-free extracts of these isolates were used to challenge indicator isolate growth.

Molecular Relationships in Biofilm Formation and the Biosynthesis of Exoproducts in Pseudoalteromonas spp.

Most members of the Pseudoalteromonas genus have been isolated from living surfaces as members of epiphytic and epizooic microbiomes on marine macroorganisms. Commonly Pseudoalteromonas isolates are reported as a source of bioactive exoproducts, i.e., secondary metabolites, such as exopolymeric substances and extracellular enzymes. The experimental conditions for the production of these agents are commonly associated with sessile metabolic states such as biofilms or liquid cultures in the stationary growth phase. Despite this, the molecular mechanisms that connect biofilm formation and the biosynthesis of exoproducts in Pseudoalteromonas isolates have rarely been mentioned in the literature. This review compiles empirical evidence about exoproduct biosynthesis conditions and molecular mechanisms that regulate sessile metabolic states in Pseudoalteromonas species, to provide a comprehensive perspective on the regulatory convergences that generate the recurrent coexistence of both phenomena in this bacterial genus. This synthesis aims to provide perspectives on the extent of this phenomenon for the optimization of bioprospection studies and biotechnology processes based on these bacteria.

Kültürü Yapılan Deniz Balıklarında Karaciğer Yağlanması ve Bakteriyel Koenfeksiyon

In the present study, we sampled sea bream and sea bass, weighing 400-450g, for routine microbiological, hematological, macroscopical and histopathological examinations. Samples were taken from seemingly healthy fish, which displayed increased feed conversion rates, signs of cold shock and slow movement. Routine bacteriological analyses included basic microbiological analyses for oxidase and catalase activity, Gram staining and O/F fermentation using API test kits. Furthermore, 16S rRNA gene sequencing was performed for identification. Serum biochemical and hematological values were determined using a Vetscan®VS2 analyzer and blood smears. Internal organs were examined by routine histopathological techniques. Hepatic fat accumulation and necrosis were noted, and liver damage was observed to be associated with significant alterations in liver enzymes. Due to multi-organ dysfunction and serious hematological disorders, primarily Vibrio alginolyticus also Alteromonas and Pseudoalteromonas species were isolated from the affected fish and co-infections were detected.

Molecular Basis of Wrinkled Variants Isolated From Pseudoalteromonas lipolytica Biofilms.

Many Pseudoalteromonas species are dominant biofilm-forming Gammaproteobacteria in the ocean. The formation of Pseudoalteromonas biofilms is often accompanied by the occurrence of variants with different colony morphologies that may exhibit increased marine antifouling or anticorrosion activities. However, the genetic basis of the occurrence of these variants remains largely unexplored. In this study, we identified that wrinkled variants of P. lipolytica mainly arose due to mutations in the AT00_08765, a wspF-like gene, that are associated with decreased swimming motility and increased cellulose production. Moreover, we found that the spontaneous mutation in flhA, encoding a flagellar biosynthesis protein, also caused a wrinkled colony morphology that is associated with cellulose overproduction, indicating that flhA plays a dual role in controlling flagellar assembly and polysaccharide production in P. lipolytica. Investigation of wrinkled variants harboring spontaneous mutation in dgcB, encoding a GGDEF domain protein, also demonstrated dgcB plays an important role in regulating cellulose production and swimming motility. In addition, by screening the suppressor of the AT00_08765 variant strain, we also identified that the spontaneous mutation in cheR and bcsC directly abolished the wrinkled phenotype of the AT00_08765 variant strain, suggesting that the chemosensory signaling transduction and cellulose production are crucial for the determination of the wrinkled phenotype in P. lipolytica. Taken together, this study provides insights into the genetic variation within biofilms of P. lipolytica.

Fatty Liver Disease and Bacterial Co-Infection in Cultured Marine Fish

In the present study, we sampled sea bream and sea bass, weighing 400-450g, for routine microbiological, hematological, macroscopical and histopathological examinations. Samples were taken from seemingly healthy fish, which displayed increased feed conversion rates, signs of cold shock and slow movement. Routine bacteriological analyses included basic microbiological analyses for oxidase and catalase activity, Gram staining and O/F fermentation using API test kits. Furthermore, 16S rRNA gene sequencing was performed for identification. Serum biochemical and hematological values were determined using a Vetscan®VS2 analyzer and blood smears. Internal organs were exam-ined by routine histopathological techniques. Hepatic fat accumulation and necrosis were noted, and liver damage was observed to be associated with significant alterations in liver enzymes. Due to multi-organ dysfunction and serious hematological disorders, primarily Vibrio alginolyticus also Alteromonas and Pseudoalteromonas species were isolated from the affected fish and co-infections were detected.

Short Communication: Identification of culturable marine fungi and bacteria from coastal region in Brunei Darussalam

Abstract. Taha H, Shivanand P, Zainudin MAA, Hadanan NA. 2021. Short Communication: Identification of culturable marine fungi and bacteria from coastal region in Brunei Darussalam. Biodiversitas 22: 1326-1331. Microbial diversity in Brunei Darussalam located on northwest coast of Borneo is not well explored. This study aimed to isolate and identify culturable marine fungi and bacteria from coastal regions. Microbial identification was carried out via DNA barcoding using rRNA-ITS marker for fungi and 16S rRNA marker for bacteria. Nine marine fungal isolates were identified to five genera as Aspergillus, Penicillium, Phialemoniopsis, Purpureocillium and Trametes. However, only one genus, Pseudoalteromonas was identified from ten marine bacterial isolates with at least three different Pseudoalteromonas species expected from the isolation. This study provided an insight into the diversity of culturable marine microbes from a coastal ecosystem. As the microbes were found culturable and can easily grow under saline conditions, they are potential of considerable biotechnological interest.

Characterization of Prodiginine Pathway in Marine Sponge-Associated Pseudoalteromonas sp. PPB1 in Hilo, Hawai‘i

Interest in bioactive pigments stems from their ecological role in adaptation, as well as their applications in various consumer products. The production of these bioactive pigments can be from a variety of biological sources, including simple microorganisms that may or may not be associated with a host. This study is particularly interested in the marine sponges, which have been known to harbor microorganisms that produce secondary metabolites like bioactive pigments. In this study, marine sponge tissue samples were collected from Puhi Bay off the Eastern shore of Hilo, Hawai‘i and subsequently were identified as Petrosia sp. with red pigmentation. Using surface sterilization and aseptic plating of sponge tissue samples, sponge-associated microorganisms were isolated. One isolate (PPB1) produced a colony with red pigmentation like that of Petrosia sp., suggesting an integral relationship between this particular isolate and the sponge of interest. 16S characterization and sequencing of PPB1 revealed that it belonged to the Pseudoalteromonas genus. Using various biological assays, both antimicrobial and antioxidant bioactivity was shown in Pseudoalteromonas sp. PPB1 crude extract. To further investigate the genetics of pigment production, a draft genome of PPB1 was sequenced, assembled, and annotated. This revealed a prodiginine biosynthetic pathway and the first cited-incidence of a prodiginine-producing Pseudoalteromonas species isolated from a marine sponge host. Further understanding into the bioactivity and biosynthesis of secondary metabolites like pigmented prodiginine may uncover the complex ecological interactions between host sponge and microorganism.

Slr4, a newly identified S-layer protein from marine Gammaproteobacteria, is a major biofilm matrix component.

S‐layers are paracrystalline proteinaceous lattices that surround prokaryotic cells, forming a critical interface between the cells and their extracellular environment. Here, we report the discovery of a novel S‐layer protein present in the Gram‐negative marine organism, Pseudoalteromonas tunicata D2. An uncharacterized protein (EAR28894) was identified as the most abundant protein in planktonic cultures and biofilms. Bioinformatic methods predicted a beta‐helical structure for EAR28894 similar to the Caulobacter S‐layer protein, RsaA, despite sharing less than 20% sequence identity. Transmission electron microscopy revealed that purified EAR28894 protein assembled into paracrystalline sheets with a unique square lattice symmetry and a unit cell spacing of ~9.1 nm. An S‐layer was found surrounding the outer membrane in wild‐type cells and completely removed from cells in an EAR28894 deletion mutant. S‐layer material also appeared to be “shed” from wild‐type cells and was highly abundant in the extracellular matrix where it is associated with outer membrane vesicles and other matrix components. EAR28894 and its homologs form a new family of S‐layer proteins that are widely distributed in Gammaproteobacteria including species of Pseudoalteromonas and Vibrio, and found exclusively in marine metagenomes. We propose the name Slr4 for this novel protein family.

Study on the degradation performance and bacterial community of bioaugmentation in petroleum-pollution seawater

Biodegradation, a widely used treatment for petroleum-pollution seawater, except for its effective degradation, the degradation performance and restoration advantages are also worth studying. In this paper, petroleum-degrading bacteria (P1) with biosurfactant-producing bacteria (B2) were used to perform bioaugmentation. The degradation performance and restoration advantages during bioaugmentation were analyzed by UV spectrophotometry and high-throughput sequencing. The results indicated the degradation rate of diesel by bioaugmentation was 71.86 % in 45 days which exceed 38 % to that without bioaugmentation. In addition, the bacterial community of seawater altered after diesel exposure, especially the species of Pseudoalteromonas and Candidatus palagibacter. During bioaugmentation, Shannon index increased from 1.91 to 2.74, and bacterial community diversity of seawater recovered after a period of time.

Characterization of Biofilm Forming Marine Pseudoalteromonas spp

Biofilm forming bacteria are omnipresent in the marine environment. Pseudoalteromonas is one of the largest within the γ-proteobacteria class, and a member of marine bacteria. Species of Pseudoalteromonas are generally found in association with marine eukaryotes. In this work, we present the isolation and characterization of two strains forming biofilm on rock surface and associated with marine sponge. They were identified using 16SrDNA as Pseudoalteromonas prydzensis alex, and Pseudoalteromonas sp. alex. They showed the highest titer in biofilm formation quantified using the test tube method using crystal violet.

Insights into the \u03ba/\u03b9-carrageenan metabolism pathway of some marine Pseudoalteromonas species

Pseudoalteromonas is a globally distributed marine-associated genus that can be found in a broad range of aquatic environments, including in association with macroalgal surfaces where they may take advantage of these rich sources of polysaccharides. The metabolic systems that confer the ability to metabolize this abundant form of photosynthetically fixed carbon, however, are not yet fully understood. Through genomics, transcriptomics, microbiology, and specific structure-function studies of pathway components we address the capacity of newly isolated marine pseudoalteromonads to metabolize the red algal galactan carrageenan. The results reveal that the κ/ι-carrageenan specific polysaccharide utilization locus (CarPUL) enables isolates possessing this locus the ability to grow on this substrate. Biochemical and structural analysis of the enzymatic components of the CarPUL promoted the development of a detailed model of the κ/ι-carrageenan metabolic pathway deployed by pseudoalteromonads, thus furthering our understanding of how these microbes have adapted to a unique environmental niche.

Ultra-small pyomelanin nanogranules abiotically derived from bacteria-secreted homogentisic acid show potential applications in inflammation and cancer

Melanins are a ubiquitous group of pigments widely acclaimed as potent free-radical scavengers. The present study proposed to harness this property of melanins for anti-inflammatory and anti-cancer applications. Pyomelanin, a potent form of melanin analogous to alkaptomelanin in humans, was derived from Pseudoalteromonas species and fabricated into ultra-small pyomelanin nanogranules (PNGs) by facile routes. These melanin nanogranules were characterized for various physicochemical attributes using DLS, TEM, FTIR, EPR, XRD, and TGDA. Additionally, elemental analysis and long-term particle stability study was also conducted. The ultra-small particles were ~ 5–7 nm in size through TEM with a very strict size distribution. The free-radical scavenging activity of PNG assessed through the DPPH assay was comparable with that of ascorbic acid. Significant inflammatory markers viz., cyclooxygenase, lipoxygenase, myeloperoxidase, and cellular nitrate levels estimated in lipopolysaccharide-triggered RAW264.7 cells were reduced upon PNG treatment. The cancer cell kill effect of PNG was estimated in lung carcinoma cells in comparison with normal fibroblasts, wherein percentage inhibition in cancer cells was ~ 2-fold higher than that observed in normal fibroblasts. Overall, our results demonstrate the proof-of-principle of using pyomelanin nanogranules for therapeutic applications.

Antibiotic Korormicin A Kills Bacteria by Producing Reactive Oxygen Species.

Korormicin is an antibiotic produced by some pseudoalteromonads which selectively kills Gram-negative bacteria that express the Na+-pumping NADH:quinone oxidoreductase (Na+-NQR.) We show that although korormicin is an inhibitor of Na+-NQR, the antibiotic action is not a direct result of inhibiting enzyme activity. Instead, perturbation of electron transfer inside the enzyme promotes a reaction between O2 and one or more redox cofactors in the enzyme (likely the flavin adenine dinucleotide [FAD] and 2Fe-2S center), leading to the production of reactive oxygen species (ROS). All Pseudoalteromonas contain the nqr operon in their genomes, including Pseudoalteromonas strain J010, which produces korormicin. We present activity data indicating that this strain expresses an active Na+-NQR and that this enzyme is not susceptible to korormicin inhibition. On the basis of our DNA sequence data, we show that the Na+-NQR of Pseudoalteromonas J010 carries an amino acid substitution (NqrB-G141A; Vibrio cholerae numbering) that in other Na+-NQRs confers resistance against korormicin. This is likely the reason that a functional Na+-NQR is able to exist in a bacterium that produces a compound that typically inhibits this enzyme and causes cell death. Korormicin is an effective antibiotic against such pathogens as Vibrio cholerae, Aliivibrio fischeri, and Pseudomonas aeruginosa but has no effect on Bacteroides fragilis and Bacteroides thetaiotaomicron, microorganisms that are important members of the human intestinal microflora.IMPORTANCE As multidrug antibiotic resistance in pathogenic bacteria continues to rise, there is a critical need for novel antimicrobial agents. An essential requirement for a useful antibiotic is that it selectively targets bacteria without significant effects on the eukaryotic hosts. Korormicin is an excellent candidate in this respect because it targets a unique respiratory enzyme found only in prokaryotes, the Na+-pumping NADH:quinone oxidoreductase (Na+-NQR). Korormicin is synthesized by some species of the marine bacterium Pseudoalteromonas and is a potent and specific inhibitor of Na+-NQR, an enzyme that is essential for the survival and proliferation of many Gram-negative human pathogens, including Vibrio cholerae and Pseudomonas aeruginosa, among others. Here, we identified how korormicin selectively kills these bacteria. The binding of korormicin to Na+-NQR promotes the formation of reactive oxygen species generated by the reaction of the FAD and the 2Fe-2S center cofactors with O2.

Diversity and Distribution of Bacteria Producing Known Secondary Metabolites.

There is an increasing interest in the utilisation of marine bioactive compounds as novel biopharmaceuticals and agrichemicals; however, little is known about the environmental distribution for many of these molecules. Here, we aimed to elucidate the environmental distribution and to detect the biosynthetic gene clusters in environmental samples of four bioactive compounds, namely violacein, tropodithietic acid (TDA), tambjamine and the antibacterial protein AlpP. Our database analyses revealed high bacterial diversity for AlpP and violacein producers, while TDA-producing bacteria were mostly associated with marine surfaces and all belonged to the roseobacter group. In contrast, the tambjamine cluster was only found in the genomes of two Pseudoalteromonas species and in one terrestrial species belonging to the Cupriavidus genus. Using a PCR-based screen of different marine samples, we detected TDA and violacein genes associated with the microbiome of Ulva and Protohyale niger and tambjamine genes associated with Nodilittorina unifasciata; however, alpP was not detected. These results highlight the variable distribution of the genes encoding these four bioactive compounds, including their detection from the surface of multiple marine eukaryotic hosts. Determining the natural distribution of these gene clusters will help to understand the ecological importance of these metabolites and the bacteria that produce them.

The art of adapting to extreme environments: The model system Pseudoalteromonas.

Extremophilic microbes have adapted to thrive in ecological niches characterized by harsh chemical/physical conditions such as, for example, very low/high temperature. Living organisms inhabiting these environments have developed peculiar mechanisms to cope with extreme conditions, in such a way that they mark the chemical-physical boundaries of life on Earth. Studying such mechanisms is stimulating from a basic research viewpoint and because of biotechnological applications. Pseudoalteromonas species are a group of marine gamma-proteobacteria frequently isolated from a range of extreme environments, including cold habitats and deep-sea sediments. Since deep-sea floors constitute almost 60% of the Earth's surface and cold temperatures represent the most common of the extreme conditions, the genus Pseudoalteromonas can be considered one of the most important model systems for studying microbial adaptation. Particularly, among all Pseudoalteromonas representatives, P. haloplanktis TAC125 has recently gained a central role. This bacterium was isolated from seawater sampled along the Antarctic ice-shell and is considered one of the model organisms of cold-adapted bacteria. It is capable of thriving in a wide temperature range and it has been suggested as an alternative host for the soluble overproduction of heterologous proteins, given its ability to rapidly multiply at low temperatures. In this review, we will present an overview of the recent advances in the characterization of Pseudoalteromonas strains and, more importantly, in the understanding of their evolutionary and chemical-physical strategies to face such a broad array of extreme conditions. A particular attention will be given to systems-biology approaches in the study of the above-mentioned topics, as genome-scale datasets (e.g. genomics, proteomics, phenomics) are beginning to expand for this group of organisms. In this context, a specific section dedicated to P. haloplanktis TAC125 will be presented to address the recent efforts in the elucidation of the metabolic rewiring of the organisms in its natural environment (Antarctica).