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PubMed2025

Mining metagenomes from extremophiles as a resource for novel glycoside hydrolases for industrial applications.

The exploration of metagenomes from extremophiles has emerged as a promising approach for discovering novel glycoside hydrolases (GHs) with potential industrial applications. Extremophiles, which thrive in harsh conditions such as high salinity, extreme temperatures, and acidic or alkaline environments, produce enzymes naturally adapted to function under these conditions. This unique adaptability makes them highly desirable for industrial processes requiring robust and efficient biocatalysts. These biocatalysts reduce reliance on harsh chemicals and energy-intensive processes, contributing to greener industrial operations. This review underscores the power of metagenomics in bypassing the need to culture large libraries of extremophiles in the lab. High-throughput sequencing and bioinformatics enable the identification of novel GH-encoding genes directly from environmental DNA. While metagenomic mining has yielded promising results, challenges such as the expression of extremophile-derived genes in mesophilic hosts, low activity yields, and scalability remain. Advances in synthetic biology and protein engineering could address these bottlenecks, enabling more efficient utilization of GHs. Additionally, integrating machine learning for predictive functional annotation may accelerate the identification of high-value candidates.

Glycoside Hydrolases↗
PubMed2026

Microbial decaprenoxanthin: From understanding an extremophile-derived C50 carotenoid to its bioprocessing for large-scale applications.

Decaprenoxanthin (DPXT) is an unusual bacterial C50 carotenoid that has historically received limited attention despite its well-defined structure. For decades, carotenoid research and industrial development have been dominated by C40 carotenoids, leaving longer-chain carotenoids largely overlooked. Recent discoveries, particularly from microorganisms inhabiting Antarctic and other extreme environments, have repositioned DPXT as an adaptive pigment shaped by intense environmental pressures. Its extended polyene chain and membrane-associated behavior suggest roles in membrane stabilization and protection against ultraviolet radiation and oxidative stress, features that may hold relevance for food and biotechnological applications. This review integrates historical and recent knowledge on DPXT, covering its structural characteristics, biosynthetic pathways, ecological function, and emerging technological relevance. Special attention is given to microbial sources, particularly Actinomycetota from extreme environments, and to recent advances in microbial genomics, metabolic engineering, and sustainable bioprocess development that enable the production and exploration of C50 carotenoids beyond their native extremophilic context. The analysis highlights DPXT as a representative example of stress-resilient carotenoids, with physicochemical and membrane-interacting properties that may offer advantages for future food and biotechnological systems. Although significant challenges remain in cultivation strategies, yield optimization, and downstream recovery, advances in microbial cell factories and green extraction technologies open new opportunities for valorizing C50 carotenoids. This review bridges extremophile microbiology, carotenoid biochemistry, and sustainable food innovation, positioning DPXT as an emerging molecule that may expand the functional and structural landscape of carotenoids relevant to food science.

Carotenoids↗
PubMed2026

Genome-scale insights into metabolic streamlining and photosynthetic energy balance in the extremophile green alga Picocystis salinarum (Picocystophyceae, Chlorophyta).

Picocystis salinarum is an early-diverging chlorophyte and the sole described member of the Picocystophyceae, frequently dominating hypersaline and alkaline lakes despite extreme physicochemical constraints. To elucidate the genomic foundations of its ecological success, we generated a fully annotated, chromosome-scale nuclear genome assembly of the type strain originally isolated from a saline pond in San Francisco Bay. The 18.5-Mb genome comprises 30 chromosomal assemblies, exhibits clear diploidy, and contains multiple copies of intact Ty3/Gypsy and Ty1/Copia long terminal repeat retrotransposons encoding polyproteins with atypical accessory domains. Phylogenomic analyses reveal strong affinity with the Nephroselmidophyceae. Comparative analyses reveal extensive metabolic streamlining, including the absence of a queuosine salvage pathway, the 2-methylcitrate cycle, β-oxidation of propionate, and branched-chain amino acid catabolism, traits retained in several marine prasinophyte lineages. In contrast, the genome preserves multiple ancestral bacterial derived systems. Notably, P. salinarum features a complete chloroplast NADH dehydrogenase-like complex, including all membrane, electron binding, and assembly components, a configuration not previously reported in sequenced chlorophyte algae. This retention implies substantial capacity for cyclic electron flow and chlororespiration, processes expected to be critical in chronically low-light and chemically extreme environments. The genome further reveals a distinctive biochemical CO2-concentrating mechanism centered on plastid-targeted phosphoenolpyruvate carboxykinase, complete plastid peptidoglycan biosynthetic and remodeling pathways, and partial retention of lipid-A-related machinery. Conversely, P. salinarum lacks canonical non-photochemical quenching proteins while retaining xanthophyll-cycle enzymes that support slower photoprotective responses. Together, these features define a coordinated genomic architecture that underpins the specialization of P. salinarum to hypersaline, alkaline, and persistently low-light ecosystems.

3‐deoxy‐D‐manno‐octulo↗
PubMed2025

CRISPR-based gene knockout in the model haloarchaeon Haloferax mediterranei.

Halophilic archaea, a specialized group of extremophiles that inhabit hypersaline environments, exhibit distinctive physiological and metabolic features. Traditional genetic manipulation of these organisms, predominantly reliant on homologous recombination techniques, suffers from limitations such as complex procedures and extended timelines, which hinder functional genomics research and the development of practical applications. This study established a CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-mediated gene knockout system in the model halophilic archaeon Haloferax mediterranei. A polyethylene glycol (PEG)-mediated transformation method was used to deliver a plasmid carrying a mini-CRISPR array into H. mediterranei. The crtB gene, involved in pigment synthesis, was successfully knocked out, demonstrating the feasibility of CRISPR-based editing in H. mediterranei. To further validate the reliability and targeting accuracy of the system, the hlyR4 gene, encoding an extracellular serine protease, was also disrupted. The CRISPR-mediated gene knockout efficiency for hlyR4 reached 27%, significantly higher than the approximately 3% efficiency achieved with conventional homologous recombination. The establishment of this CRISPR-based gene knockout system provides a more efficient genetic tool for H. mediterranei and lays a new experimental foundation for exploiting microbial resources from extreme environments. In this study, H. mediterranei was selected as the model organism for haloarchaea. For the first time, we successfully constructed a CRISPR-based gene knockout system in a model halophilic archaeon. This system provides a solution for CRISPR-based gene knockout tools, which are currently unavailable in model halophilic archaea, and offers an effective tool for functional genomics studies in extremophiles.

Haloferax mediterranei↗
PubMed2026

Thermophilic bacteria of the Arabian Gulf and their emerging biotechnological applications: current insights and future prospects.

Thermophilic bacteria represent a powerful class of extremophiles whose ability to thrive at elevated temperatures makes them indispensable to modern biotechnology. The Arabian Gulf characterized by extreme heat, geothermal systems, hot springs, oil reservoirs, and hypersaline habitats hosts a rich yet understudied reservoir of these organisms. This review consolidates current insights into the diversity, ecological niches, and biotechnological relevance of thermophilic bacteria isolated from the region. Dominant genera such as Bacillus, Geobacillus, Thermus, Anoxybacillus, and Brevibacillus exhibit remarkable physiological and molecular strategies that enable survival under intense thermal, saline, and pH stress. Their capacity to produce thermostable enzymes, including proteases, amylases, lipases, cellulases, and DNA polymerases, positions them as high-value contributors to sectors spanning bioenergy, pharmaceuticals, food processing, agriculture, and environmental remediation. Beyond enzyme production, emerging applications such as antimicrobial compound discovery, hydrocarbon bioremediation, wastewater treatment, and sustainable bioprocessing highlight the region's untapped biotechnological potential. However, systematic exploration remains limited, hindered by sparse isolation efforts, incomplete physiological profiling, and a lack of genomic and omics-driven studies. The review underscores the need for integrated approaches that merge classical microbiology with advanced molecular and systems-level tools. Collectively, thermophilic bacteria from the Arabian Gulf constitute a promising yet underutilized biological resource poised to drive sustainable industrial innovation and environmental solutions.

Arabian Gulf↗
PubMed2025

A deep metagenomic atlas of Qinghai-Xizang Plateau lakes reveals their microbial diversity and salinity adaptation mechanisms.

The Qinghai-Xizang Plateau (QXP), harboring the planet's highest density of plateau lakes, offers an exceptional biogeographic environment for studying extremophilic microbial communities and their adaptation to salinity. Through deep metagenomic sequencing, we construct the Qinghai-Xizang Lake Sediment Genome (QXLSG) catalog, a high-resolution genomic catalog comprising 5,866 metagenome-assembled genomes (MAGs), 58.16 million non-redundant protein encoding genes, and 19,008 biosynthetic gene clusters. Notably, 80.78% of the 2,742 species-level MAGs represent undescribed taxa, significantly expanding the known microbial diversity. Salinity emerges as the primary environmental factor influencing microbial community. Functional annotation highlights that the "salt-out" strategy, particularly the uptake of glycine betaine, is the main mechanism for salinity tolerance. This strategy is prevalent in both hypersaline lake communities and the dominant microbial phyla. Overall, this study provides a crucial genetic resource for future bioprospecting and deepens our understanding of the fundamental mechanisms of microbial adaptation to extreme saline environments.

Lakes↗
PubMed2025

Biochemical and Structural Analyses of the Tardigrade DNA-Damage Suppressor Protein, Dsup.

Tardigrades are extremophiles that withstand harsh environments through unique molecular strategies. One such strategy involves Damage Suppressor (Dsup), a protein shown to protect cells from radiation-induced DNA damage. Little is known about the biochemical and structural characteristics of Dsup that lead to DNA protection. To gain insight into the mechanism of DNA protection by Dsup, we examined its fundamental biochemical and structural properties using mass photometry, biolayer interferometry, small-angle X-ray scattering, and microfluidic modulation spectroscopy. We found that Dsup is largely intrinsically disordered and binds DNA with high affinity via a multi-valent interface. This interaction induced conformational changes in both Dsup and the DNA, suggesting a potential structural mechanism of its DNA protection ability. We propose that Dsup alters DNA structure, possibly by partially unwinding it, to reduce its susceptibility to damage. These findings offer new insights into how a disordered protein such as Dsup functions as radioprotectants in extreme environments.

Tardigrada↗
PubMed2026

Deep subsurface organic-rich shale supports abundant, diverse, and novel fungi.

As Earth's principal reservoir of organic carbon and microbial biomass, the deep subsurface hosts microorganisms capable of mobilizing this once-sequestered carbon. Contrary to standard assumptions of eukaryotic scarcity, this study documents abundant fungal communities, ranging from 4.2 × 103 to 6.8 × 103 fungal cells ml-1, across a methane-producing organic-rich shale 247-556 meters below the surface. Although fungal:bacterial cell ratios ranged from 1:7028 to 1:713, application of biomass conversion factors developed for oceanic systems yielded a median fungal:bacterial biomass ratio of 1:4.7. 16S ribosomal ribonucleic acid (rRNA) gene amplicons revealed bacterial and archaeal communities mirroring those found in well-characterized extremophilic, carbon-degrading environments, while sequencing of 18S rRNA gene and internal transcribed spacer rRNA spacer amplicons collectively identified a eukaryotic hotspot with 689 fungal operational taxonomic units across six phyla. The dominant fungal classes, Agaricomycetes and Dothideomycetes, are well-established degraders of recalcitrant carbon compounds at the surface, suggesting they may similarly contribute to organic matter degradation and ecosystem maintenance in the subsurface. Cultivation and isolation efforts yielded 205 fungal strains, including 13 candidate novel taxa, underscoring the deep subsurface as an underexplored eukaryotic habitat. Stable carbon isotopes indicate methane is predominantly generated via microbial conversion of the fossil carbon, while water isotopes suggest in situ geochemical conditions have been relatively stable since the Late Pleistocene, with subglacial recharge as a plausible mechanism for microbial introduction. Collectively, these findings suggest that fungi are underrecognized contributors to organic matter transformation and functional diversity in the deep biosphere, revealing a critical gap in our understanding of deep subsurface ecosystem processes.

Fungi↗
PubMed2025

Genomic signatures of innovation and selection in the extremotolerant yeast Kluyveromyces marxianus.

Extremophiles can be the product of millions of years of evolutionary engineering and refinement. The underlying mechanisms can be quite distinct from the ones operating at earlier stages of trait innovation. In this work, we have developed the compost yeast Kluyveromyces marxianus, which diverged from its closest relative >20 million years ago, as a model for interspecies comparative biology and genomics. We applied a battery of growth assays to species of the Kluyveromyces genus and found that K. marxianus outperformed its relatives in a battery of heat and chemical stress conditions. We then generated and analyzed genomes from across the genus, to find derived genetic features associated with, and potentially causal for, K. marxianus traits. We found robust expansions in gene families in the K. marxianus genome, most notably among genes annotated as transmembrane transporters and in metabolism. In molecular-evolution tests, we identified adaptive protein variants at hundreds of genes, among which plasma membrane transporters were over-represented. Together, these signals enable a model for the molecular mechanisms and evolutionary pressures underlying K. marxianus traits, including gains in transporter function mediating stress resistance, and metabolic variants contributing to its capacity for rapid growth in challenging conditions. Such oligogenic architectures may be the rule rather than the exception in phenotypes that have evolved over long timescales.

Journal Article↗
PubMed2025

Cross-species phenotypic profiling uncovers functional determinants of bacterial cold shock adaptation.

Temperature shifts impose broad physiological stress, requiring precise and dynamic regulatory programs to restore cellular homeostasis. While the heat shock response is well characterized, the mechanisms underlying cold shock response (CSR) remain less understood. To identify genes critical for cold adaptation, we applied transposon sequencing (Tn-seq) to monitor mutant fitness across the full course of CSR and sustained low-temperature growth in two mesophilic bacteria, Escherichia coli and Bacillus subtilis. In B. subtilis, phenotypic profiling revealed a temporally structured program: membrane fluidity and cell wall remodeling were most critical in the early stage of CSR, whereas post-transcriptional regulation became essential during late-stage recovery to reprogram gene expression and restore growth. Cross-species comparison uncovered both conserved and species-specific mechanisms, with RNA metabolism and ribosome/translation regulators playing broad roles. Specifically, we identified a conserved synergy between two ribosomal RNA methyltransferases, RsmA and RsmH, in promoting cold adaptation. In B. subtilis, mutants lacking these enzymes exhibited significant delay in translation recovery following cold-induced global inhibition. Together, these findings provide a comparative, systems-level view of bacterial cold adaptation and establish a framework for exploring stress responses in pathogens and extremophiles.

Cell envelope↗
PubMed2026

Genome mining of alkaliphilic cyanobacterial consortia: identification of biosynthetic gene clusters in Sodalinema and associated heterotrophs.

Alkaline soda lakes are high-pH environments that host specialized microbial communities with potential for biotechnology and natural product discovery. We characterized three Sodalinema-dominated cyanobacterial consortia enriched from Canadian soda lakes over 510 days. Using hybrid metagenomic sequencing and metatranscriptomics across pH, alkalinity, and temperature gradients, we reconstructed high-quality metagenome-assembled genomes and assessed functional activity. All consortia converged toward cyanobacteria dominance and exhibited temperature optima between 21°C and 30°C. Phylogenetic analysis placed Sodalinema genomes within a distinct clade affiliated with Candidatus Sodalinema alkaliphilum. Genomic analysis indicated complete biosynthetic pathways for vitamin B5, vitamin B7, and the molybdenum cofactor, but incomplete pathways for vitamins B1, B9, and B12, consistent with patterns observed in Sodalinema yuhuli. Metatranscriptomic profiles showed increased expression of genes involved in phycocyanin and carotenoid biosynthesis at pH 10.2 relative to pH 8.5. Biosynthetic gene cluster analysis revealed that most secondary metabolic potential resided in heterotrophic community members. Roseinatronobacter encoded pathways for N-acyl homoserine lactones, osmoprotectants, betalactones, and prodigiosin, while Alkalimonas, Wenzhouxiangella, and members of the Kiloniellales encoded clusters for lanthipeptides, cyclodipeptides, hydrogen cyanide, and pyrroloquinoline quinone. These findings indicate functional partitioning within the consortia and highlight the contribution of heterotrophs to secondary metabolism.IMPORTANCEAlkaline soda lakes contain microbial communities adapted to high pH that remain underexplored for biotechnology. This study focuses on Sodalinema, a filamentous cyanobacterium that dominates enriched consortia from Canadian soda lakes, and its associated heterotrophic partners. We show that while Sodalinema drives primary productivity, heterotrophic bacteria encode most of the pathways for antimicrobial and signaling compounds. These interactions may support community stability and defense against competing microorganisms. By linking genomic potential with gene expression, this work identifies alkaline cyanobacterial consortia as a source of bioactive compounds and provides a framework for exploring extremophilic microbial communities for natural product discovery.

Sodalinema↗
PubMed2026

Comparative metagenomic analysis of microbial communities: unravelling microbial communities from the great Rann of Kachchh and coastal saltpans, Gujarat, India.

Hypersaline environments exhibit extreme physiochemical conditions yet support diverse microbial communities. These communities are not only ecologically important but also possess substantial potential for biotechnological exploitation. In this study, we employed a comparative metagenomic approach to assess microbial diversity using two distinct methodologies: (1) direct DNA extraction from raw sediment, and (2) DNA extraction following halophilic enrichment in selective media. Sediment samples were collected from multiple sites and pooled together within the Rann of Kachchh and close-by saltpans and were analysed using 16S rRNA sequencing coupled with bioinformatics pipelines. The results revealed pronounced differences in microbial community composition between the two approaches. Raw sediment samples exhibited significantly higher alpha diversity, with dominant taxa including Halobacterota, Cyanobacteria, and Desulfobacterota, with a substantial proportion of unclassified genera. In contrast, enriched samples were dominated by fast-growing, culturable genera such as Halobacterium, Alkalibacillus, and Candidatus haloredivivus. Principal Coordinate Analysis (PCoA) of beta diversity demonstrated distinct clustering between raw and enriched communities, even within samples from the same sites, underscoring the selective bias introduced by enrichment procedures. These findings emphasise that the methodological choice strongly influences the observed microbial diversity. The aim of this study was to compare microbial community composition in raw hypersaline sediments and enrichment cultures using metagenomic sequencing, to evaluate how enrichment selectively favours specific halophilic taxa. This comparative approach allows identification of the microbial groups that rapidly proliferate under controlled hypersaline conditions, thereby complementing direct environmental sequencing. By integrating both direct and enrichment-based metagenomic approaches, a more comprehensive understanding of microbial community structure in hypersaline environments can be achieved.

India↗