Leticia Barrientos

Macroalgae and their associated microbes form tightly integrated holobionts, yet cross‐study comparisons of epiphytic microbiomes remain constrained by heterogeneous sampling designs, primer selection, and analytical pipelines. We performed a harmonized meta‐analysis of publicly available 16S rRNA gene datasets to examine diversity, community structure, and inferred functional profiles within a common analytical framework. A structured search identified 16 studies, totaling 763 samples, from macroalgae and adjacent seawater across four oceanic regions. All datasets were reprocessed using a standardized workflow to ensure cross‐study comparability. The compiled dataset was strongly skewed towards brown macroalgae (Phaeophyceae) and the V4 region of the 16S gene, highlighting both the prominence of Laminariales in current research and the need for methodological harmonization. Within this framework, alpha diversity differed among macroalgal orders, with Fucales hosting the richest epiphytic assemblages, Desmarestiales intermediate diversity, and Laminariales the lowest, while seawater exhibited intermediate values. Community composition was structured by host taxonomic identity and sample type. Within Laminariales, thalli supported assemblages distinct from seawater, sharing a limited taxonomic core and displaying reproducible genus‐level signatures. Trait‐based functional annotation indicated enrichment of aerobic chemoheterotrophy and polysaccharide‐associated metabolisms in Laminariales communities, whereas seawater showed greater representation of nitrogen‐ and sulfur‐related processes. These findings demonstrate that cross‐study reprocessing resolves consistent host‐associated patterns and establishes a quantitative framework for future multi‐omics and experimental investigations.

This study presents the first annotated genome of the Antarctic fungus Pseudogymnoascus australis UA-032-E, revealing significant biosynthetic potential with 44 predicted biosynthetic gene clusters (BGCs) identified through antiSMASH analysis. These BGCs include nonribosomal peptide synthetases (NRPS), type I polyketide synthases (PKS), and hybrid systems, indicating a diverse capacity for secondary metabolite production. BiG-SCAPE analysis grouped these clusters into 41 gene cluster families, with most being singletons, demonstrating low genetic redundancy and high structural diversity. To activate silent pathways, we employed elicitors (NPS and LPS) across multiple culture media, successfully inducing previously undetected metabolic activity. Using an integrated LC–QTOF–MS/MS approach combined with the GNPS and SIRIUS platforms, a total of 75 features were detected, including cyclodipeptides [cyclo-(Pro-Val), cyclo-(Leu-Leu)], maculosin, and betaine lipids such as DGTS 18:2—compounds linked to stress adaptation and biological activities in the literature. The YES medium supplemented with LPS elicitation yielded the highest metabolic diversity, suggesting this combination effectively stimulates specialized metabolism. Our findings demonstrate the value of combining genomic and metabolomic approaches to unlock the chemical potential of psychrophilic fungi. The genomic resource presented here provides a foundation for future functional studies and targeted bioprospecting of this Antarctic fungus for novel metabolites with potential biotechnological applications.

Identifying the microbial taxa that structure assemblages in response to local disturbances along the Chilean Patagonian coast is critical for understanding community reorganization and ecological risk in this vulnerable marine environment. Here, we examined benthic microbial interactions across sixteen sites spanning 42–44°S in the Inner Sea of Chiloé and adjacent fjord systems. Using co-occurrence network analysis, we characterized spatial interaction patterns and identified keystone taxa whose relationships with environmental variables may serve as ecological indicators. The presence of keystone taxa supports the concept of microbial “seed banks,” which sustain community stability and ecosystem functionality under stress. Networks revealed structured communities dominated by niche-specialist taxa, consistent with ecological processes of niche differentiation and environmental filtering. The benthic environment was found to harbor niche-specialist taxa, including Flavobacteriaceae, Gemmataceae, Humimicrobiaceae, Clostridiaceae, and Sulfurovaceae, typically associated with organic enrichment and anthropogenic influence. These microbial families showed strong correlations with environmental gradients such as nitrate, phosphate, silicate, pH, salinity, and phaeopigments. Alpha-diversity analyses revealed greater microbial richness in FZ compared to the ISC, likely reflecting higher environmental heterogeneity and long-term adaptation to dynamic and fluctuating conditions. Beta-diversity analyses further supported the presence of distinct microbial assemblages between the two zones. Multivariate statistics and co-occurrence network analyses demonstrated that FZ communities display enhanced taxonomic interactions and greater network complexity, suggesting increased ecological stability. In contrast, microbial networks in the ISC exhibited reduced connectivity, potentially indicative of environmental stressors disrupting microbial spatial organization and network resilience. Moreover, the identification of indigenous bacterial isolates provided evidence for the presence of opportunistic host-associated pathogens, highlighting the utility of microbial biomarkers in detecting early ecological responses to human impacts. Microbial co-occurrence patterns in northern Patagonian sediments reveal shifts in community assembly and increased network complexity that may enhance resilience to perturbations. The detection of strains harboring opportunistic pathogen biomarkers highlights risks under intense anthropogenic pressures. Monitoring keystone taxa thus offers early warning of functional decline. Broader spatio-temporal assessments remain essential to clarify microbial dynamics and their implications for ecosystem health and antimicrobial resistance.

The growing threat of antimicrobial resistance has intensified the search for new bioactive compounds, particularly in extreme environments such as Antarctica. Streptomyces fildesensis So13.3, isolated from Antarctic soil, harbours a biosynthetic gene cluster (BGC) associated with actinomycin D production, an antibiotic with biomedical relevance. This study investigates the regulatory role of TetR/AcrR transcription factors encoded within this biosynthetic gene cluster (BGC), focusing on their structural features and expression under different nutritional conditions. Additionally, we propose that repressing an active pathway could lead to the activation of silent biosynthetic routes, and our in-silico analysis provides a foundation for selecting key mutations and experimentally validating this strategy. Expression analysis revealed that TetR-279, in particular, was upregulated in ISP4 and IMA media, suggesting its participation in nutrient-dependent BGC regulation. Structural modelling identified key differences between TetR-206 and TetR-279, with the latter containing a tetracycline-repressor-like domain. Molecular dynamics simulations confirmed TetR-279’s structural stability but showed that the S166P CRISPy-web-guided mutation considerably affected its flexibility, while V167A and V167I had modest effects. These results underscore the importance of integrating omics, structural prediction, and gene editing to evaluate and manipulate transcriptional regulation in non-model bacteria. Targeted disruption of TetR-279 may derepress actinomycin biosynthesis, enabling access to silent or cryptic secondary metabolites with potential pharmaceutical applications.

Antarctic microorganisms have genomic characteristics and biological functions to ensure survival in complex habitats, potentially representing bioactive compounds of biotechnological interest. Pseudarthrobacter sp. So.54 is an Antarctic bacteria strain isolated from the rhizospheric soil of Colobanthus quitensis. Our work aimed to study its genomic characteristics and metabolic potential, linked to environmental adaptation and the production of secondary metabolites with possible biotechnological applications. Whole-genome sequencing, assembly, phylogenetic analysis, functional annotation, and genomic islands prediction were performed to determine the taxonomic affiliation and differential characteristics of the strain So.54. Additionally, Biosynthetic Gene Clusters (BGCs) responsible for secondary metabolites production were identified. The assembled genome of strain So.54 has 3,871,805 bp with 66.0% G + C content. Phylogenetic analysis confirmed that strain So.54 belongs to the Pseudarthrobacter genus; nevertheless, its nucleotide and amino acid identity values were below the species threshold. The main metabolic pathways and 64 genomic islands associated with stress defense and environmental adaptation, such as heavy metal resistance genes, were identified. AntiSMASH analysis predicted six BGCs with low or no similarity to known clusters, suggesting potential as novel natural products. These findings indicate that strain So.54 could be a novel Pseudarthrobacter species with significant environmental adaptation and biotechnological potential.

The growing threat of antimicrobial resistance has driven the search for new bioactive compounds in extreme environments such as Antarctica. Streptomyces fildesensis So13.3, isolated from Antarctic soil, has been shown to contain a biosynthetic gene cluster associated with producing actinomycin D, an antibiotic with therapeutic potential. In this study, we analysed the regulatory role of TetR/AcrR family transcription factors present within this BGC, focusing on their activation under different nutritional conditions and their structural scharacterisation using bioinformatics tools and molecular dynamics simulations. The results showed that TetR/AcrR expression increased significantly in ISP4 and IMA media, suggesting their involvement in nutrient-dependent regulation of the cluster. At the structural level, two TetR proteins (TetR-206 and TetR-279) were modelled, with the latter standing out due to a C-terminal tetracycline repressor-like domain. A 200 ns molecular dynamics simulation was performed in GROMACS to evaluate the stability and flexibility of TetR-279, including analysis of point mutations (S166P, V167A, V167I). The S166P mutation significantly impacted structural flexibility, while V167A and V167I caused only minor alterations. This work demonstrates the value of integrating omics approaches, structural modelling, and gene editing with CRISPR to study and potentially activate silent BGCs in non-model bacteria such as Antarctic Streptomyces. In particular, the targeted inhibition of TetR-279 may trigger metabolic rewiring and facilitate the expression of novel antibiotics encoded in cryptic biosynthetic gene clusters.

Antarctic microorganisms have genomic characteristics and biological functions to ensure survival in complex habitats, potentially representing bioactive compounds of biotechnological interest. Pseudarthrobacter sp. So.54 is an Antarctic bacteria strain isolated from the rhizospheric soil of Colobanthus quitensis. Our work aimed to study its genomic characteristics and metabolic potential, linked to environmental adaptation and the production of secondary metabolites with possible biotechnological applications. Whole-genome sequencing, assembly, phylogenetic analysis, functional annotation, and genomic islands prediction were performed to determine the taxonomic affiliation and differential characteristics of the strain So.54. Additionally, Biosynthetic Gene Clusters (BGCs) responsible for secondary metabolites production were identified. The assembled genome of strain So.54 has 3,871,805 bp with 66.0 % G + C content. Phylogenetic analysis confirmed that strain So.54 belongs to the Pseudarthrobacter genus, nevertheless, its nucleotide and amino acid identity values were below the species threshold. The main metabolic pathways and 64 genomic islands associated with stress defense and environmental adaptation, such as heavy metal resistance genes, were identified. AntiSMASH analysis predicted six BGCs with low or no similarity to known clusters, suggesting potential as novel natural products. These findings indicate that strain So.54 could be a novel Pseudarthrobacter species with significant environmental adaptation and biotechnological potential.

Natural products (NPs) are crucial for the development of novel antibiotics, anticancer agents, and immunosuppressants. To highlight the ability of fungi to produce structurally diverse NPs, this article focuses on the impact of genome mining and CRISPR-Cas9 technology in uncovering and manipulating the biosynthetic gene clusters (BGCs) responsible for NP synthesis. The CRISPR-Cas9 system, originally identified as a bacterial adaptive immune mechanism, has been adapted for precise genome editing in fungi, enabling targeted modifications, such as gene deletions, insertions, and transcription modulation, without altering the genomic sequence. This review elaborates on various CRISPR-Cas9 systems used in fungi, notably the Streptococcus pyogenes type II Cas9 system, and explores advancements in different Cas proteins for fungal genome editing. This review discusses the methodologies employed in CRISPR-Cas9 genome editing of fungi, including guide RNA design, delivery methods, and verification of edited strains. The application of CRISPR-Cas9 has led to enhanced production of secondary metabolites in filamentous fungi, showcasing the potential of this system in biotechnology, medical mycology, and plant pathology. Moreover, this article emphasizes the integration of multi-omics data (genomics, transcriptomics, proteomics, and metabolomics) to validate CRISPR-Cas9 editing effects in fungi. This comprehensive approach aids in understanding molecular changes, identifying off-target effects, and optimizing the editing protocols. Statistical and machine learning techniques are also crucial for analyzing multi-omics data, enabling the development of predictive models and identification of key molecular pathways affected by CRISPR-Cas9 editing. In conclusion, CRISPR-Cas9 technology is a powerful tool for exploring fungal NPs with the potential to accelerate the discovery of novel bioactive compounds. The integration of CRISPR-Cas9 with multi-omics approaches significantly enhances our ability to understand and manipulate fungal genomes for the production of valuable secondary metabolites and for promising new applications in medicine and industry.

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

Plant-microbiota interactions have significant effects on plant growth, health, and productivity. Rhizosphere microorganisms are involved in processes that promote physiological responses to biotic and abiotic stresses in plants. In recent years, the interest in microorganisms to improve plant productivity has increased, mainly aiming to find promising strains to overcome the impact of climate change on crops. In this work, we hypothesize that given the desertic environment of the Antarctic and the Atacama Desert, different plant species inhabiting these areas might share microbial taxa with functions associated with desiccation and drought stress tolerance. Therefore, in this study, we described and compared the composition of the rhizobacterial community associated with Deschampsia antarctica (Da), Colobanthus quitensis (Cq) from Antarctic territories, and Croton chilensis (Cc), Eulychnia iquiquensis (Ei) and Nicotiana solanifolia (Ns) from coastal Atacama Desert environments by using 16S rRNA amplicon sequencing. In addition, we evaluated the putative functions of that rhizobacterial community that are likely involved in nutrient acquisition and stress tolerance of these plants. Even though each plant microbial rhizosphere presents a unique taxonomic pattern of 3,019 different sequences, the distribution at the genus level showed a core microbiome with a higher abundance of Haliangium, Bryobacter, Bacillus, MND1 from the Nitrosomonadaceae family, and unclassified taxa from Gemmatiamonadaceae and Chitinophagaceae families in the rhizosphere of all samples analyzed (781 unique sequences). In addition, species Gemmatirosa kalamazoonesis and Solibacter usitatus were shared by the core microbiome of both Antarctic and Desert plants. All the taxa mentioned above had been previously associated with beneficial effects in plants. Also, this microbial core composition converged with the functional prediction related to survival under harsh conditions, including chemoheterotrophy, ureolysis, phototrophy, nitrogen fixation, and chitinolysis. Therefore, this study provides relevant information for the exploration of rhizospheric microorganisms from plants in extreme conditions of the Atacama Desert and Antarctic as promising plant growth-promoting rhizobacteria.