Deschampsia antarctica and Colobantus quitensis are the only two vascular plants colonized on the Antarctic continent, which is usually exposed to extreme environments. Endophytic bacteria residing within plant tissues can exhibit diverse adaptations that contribute to their ecological success and potential benefits for their plant hosts. This study aimed to characterize 12 endophytic bacterial strains isolated from these plants, focusing on their ecological adaptations and functional roles like plant growth promotion, antifungal activities, tolerance to salt and low-carbon environments, wide temperature range, and biofilm formation. Using 16S rRNA sequencing, we identified several strains, including novel species like Hafnia and Agreia. Many strains exhibited nitrogen-fixing ability, phosphate solubilization, ammonia, and IAA production, potentially benefiting their hosts. Additionally, halotolerance and carbon oligotrophy were also shown by studied bacteria. While some Antarctic bacteria remain strictly psychrophilic, others demonstrate a remarkable ability to tolerate a wider range of temperatures, suggesting that they have acquired mechanisms to cope with fluctuations in environmental temperature and developed adaptations to survive in intermediate hosts like mammals and/or birds. Such adaptations and high plasticity of metabolism of Antarctic endophytic bacteria provide a foundation for research and development of new promising products or mechanisms for use in agriculture and technology.

Endophytic bacteria, recognized for their beneficial effects on plant development and adaptation, can facilitate the survival of Antarctic plants in severe environments. Here we studied endophytes of the vascular plant Deschampsia antarctica Ė. Desv. from two distantly located regions in the maritime Antarctic: King George Island (South Shetland Islands) and Galindez Island (Argentine Islands). Bacterial group-specific PCR indicated presence of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, Cytophaga-Flavobacteria and Actinobacteria in root and leaf endosphere of D. antarctica sampled at four distinct sites of both locations. The diversity of endophytic bacteria was significantly higher in the leaves compared to the roots in plants from Galindez Island. Similarly, the diversity of endophytes was higher in the leaves rather than roots of plants from the King George Island. Twelve bacterial species were isolated from roots of D. antarctica of Galindez Island (the Karpaty Ridge and the Meteo Point) and identified by sequencing the 16S rRNA gene. Isolates were dominated by the Pseudomonas genus, followed by the genera Bacillus and Micrococcus. The vast majority of the isolates exhibited cellulase and pectinase activities, however, Bacillus spp. expressed neither of them, suggesting lack of genetic flow of these traits in endophytic bacilli in the maritime Antarctic. Pseudomonas sp. IMBG305 promoted an increase in the leaf number in most of the treated plant genotypes when compared with non-inoculated plants, and a rapid vegetation period of D. antarctica cultured in vitro, albeit the length of leaves in the treated plants was significantly lower, and flavonoid content leveled off in all treated plants. D. antarctica is known to develop diverse ecotypes with regard to ecological conditions, such as organic input, moisture or wind exposition. The D. antarctica phenotype could be extended further through the endophyte colonization, since phenotypic changes were observed in the inoculated D. antarcticaplants grown in vitro in our study. Herewith, endophytes can contribute to plant phenotypic plasticity, potentially beneficial for adaptation of D. antarctica.

Background : The interactions between the host organism and the microbiota play an important role in the host's survival, influencing its physiology and adaptation. The Antarctic, due to its extreme living conditions, is a unique region for studying such interactions. However, research on the microbiomes of Antarctic terrestrial and freshwater invertebrates remains limited, especially with regard to the region's sole endemic insect, Belgica antarctica . Our aim was to study the B. antarctica microbiome collected from different substrates and from varying ornithogenic influence levels. Methods : A total of 330 B. antarctica larvae and moss substrates were sampled at three sites with different ornithogenic impact, followed by DNA extraction using Qiagen kits. The V3-V4 region of bacterial 16S rRNA was amplified by PCR and sequenced on the Illumina NovaSeq platform, followed by bioinformatic processing in QIIME2 for OTU clustering, taxonomic classification, and diversity analysis. Further analysis and visualization was performed in R, Python and GraphPad Prism. Results : Amplicon sequencing revealed rich microbial diversity, with NMDS demonstrating clear clustering of samples according to their origin (insects vs substrate) and ornithogenic influence level. Comparative analysis revealed that the vast majority of OTUs associated with B. antarctica (ca. 95%) were shared with substrates, whereas the insect-specific fraction was small, highly variable, and partially influenced by moss species. Ornithogenic influence significantly structured the symbiotic microbiota in both insects and substrates, reducing microbial diversity and altering the relative abundance of major bacterial taxa. Overall, substrate type and ornithogenic impact are significant factors influencing microbial community structure, while insect-specific taxa formed only a minor, heterogeneous component of this midge microbiome. Additionally, the Wolbachia infection was detected in B. antarctica larvae for the first time. Conclusion : The substrate that B. antarctica inhabits, as well as ornithogenic influence, play a significant role in the shaping of the species' microbiome. This Antarctic chironomid also maintains a core microbial community. The detection of Wolbachia in B. antarctica is the first evidence of this endosymbiont in Antarctica.

Resistance of King George Island soil microbial communities to individual toxic metals and their mixture was determined. Microorganisms were cultivated in liquid medium, and growth was assessed by turbidity and direct microscopy. Maximum tolerated individual concentrations were 2000 mg/l Cu²⁺, 400 mg/l Cr(VI), 200 mg/l Ni²⁺ and 100 mg/l Co²⁺. The highest resistance was observed for copper. With four metals present simultaneously, growth persisted at a total concentration of 1300 mg/l: 1000 mg/l Cu²⁺, 150 mg/l Cr(VI), 100 mg/l Ni²⁺ and 50 mg/l Co²⁺. Resistance to the mixture was approximately half the sum of the individual tolerance values. High metal resistance is considered a feature of community homeostasis and a basis for potential biotechnological applications. Editorial note (2026): This abstract was prepared for reference purposes using artificial intelligence technology, based on the original publication, without the involvement of the author(s).

Climate change is reshaping Antarctic ecosystems, where the resilience of Deschampsia antarctica and Colobanthus quitensis is mediated by endophytic microbial communities assembled under strong abiotic drivers. This study explores the temperature-dependent biofilm development in two Antarctic endophytic microbial communities (ALS and LS). Multivariate analysis revealed a fundamental trade-off between planktonic expansion and biofilm matrix investment as a function of thermal cues. While moderate warming (15–25 °C) optimized cell viability and turbidity, extreme thermal stress at 37–42 °C in nutrient-rich conditions triggered a significant shift toward a matrix-rich signature, characterized by a synergistic increase in total DNA and cellulose. Crucially, at the thermal extreme of 42 °C, we observed a decoupling of optical density from culturable biomass, where high turbidity did not translate into viable cells, signaling a state of severe environmental stress. These results identify 25 °C as the quantitative threshold for optimal growth, while temperatures of 37–42 °C act as a specific trigger for protective matrix production. Such thermal plasticity suggests that Antarctic endophytes are evolutionarily primed for persistence not only in cold native niches but also during bird-mediated dispersal at endothermic host temperatures.