A team of mycologists and microbial ecologists from Rovira i Virgili University in Reus, Spain, led by Alan Omar Granados-Casas, Alberto Miguel Stchigel, Ana Fernández-Bravo and José Francisco Cano-Lira, compared sediment communities from two strikingly different neighbouring water bodies. Salada Grande de Chiprana is a hypersaline lagoon whose waters are far saltier than the ocean, while the nearby La Estanca is an oligohaline lagoon with only low levels of dissolved salts. By sampling both, the researchers could ask a deceptively simple question: does salinity structure the invisible communities of fungi and prokaryotes that live in lagoon sediments, and how reliable are the molecular tools used to detect them?

The team used DNA metabarcoding, a technique that extracts environmental DNA from sediment, amplifies a specific genetic marker with the polymerase chain reaction, and then sequences the resulting mixture to identify which organisms are present. For fungi, the researchers targeted the internal transcribed spacer region of the nuclear ribosomal DNA, the standard barcode for fungal identification. Crucially, they ran two versions of this marker, ITS1 and ITS2, which flank the 5.8S ribosomal RNA gene and are often treated as interchangeable in the literature. For prokaryotes, meaning bacteria and archaea, they sequenced the 16S ribosomal RNA gene, the long-standing workhorse of bacterial diversity surveys.

When the two fungal marker datasets were analysed together, the fungal communities in both lagoons were dominated by three major lineages: the phylum Ascomycota, which contains most described fungal species; the Rozellomycota, a mysterious group of obligate parasites of other microorganisms; and the Basidiomycota, which includes mushrooms and their relatives. The prokaryotic assemblages, by contrast, were composed mainly of Pseudomonadota, a hugely diverse bacterial phylum, along with Cyanobacteriota, the photosynthetic bacteria that often form conspicuous microbial mats in saline environments, plus Bacteroidota and Chloroflexota, both common in sediments rich in organic matter.

The first surprise came from the diversity estimates themselves. When the researchers counted the number of distinct amplicon sequence variants, or ASVs, in each sample, they found no significant difference in fungal alpha diversity between the hypersaline and oligohaline lagoons. In other words, the saltier environment did not appear to host a depauperate fungal community compared with its brackish neighbour. However, the choice of marker mattered: the ITS2 primer pair recovered a significantly higher number of observed ASVs than ITS1, a difference the authors report as statistically significant with a p-value of 0.016. Two markers from the same genomic region, amplified from the same sediments, delivered measurably different inventories of fungal life.

The deeper analysis sharpened that warning. Using Bray-Curtis dissimilarity, a measure of how different community compositions are between samples, combined with PERMANOVA, a permutation-based statistical test for community data, the team found that fungal community composition was significantly associated with two factors: the identity of the lagoon and the molecular marker used. Remarkably, the marker choice explained more of the variation in the fungal data than the lagoon identity itself, and there was also a significant interaction between the two, meaning the apparent effect of the lagoon depended on which marker was being examined. For a field that often draws ecological conclusions from a single marker, that is a sobering result.

Salinity, the environmental variable most obviously differentiating the two lagoons, turned out to be a weaker predictor than expected. The researchers used electrical conductivity as a proxy for salinity and found that it explained only a limited and statistically non-significant fraction of the variation in fungal community composition. The authors are careful to note an important caveat: because the two lagoons differ in more ways than one, conductivity’s independent contribution could not be cleanly separated from other environmental differences between the sites. The hypersaline lagoon is not simply a saltier version of La Estanca; it is a distinct ecosystem with its own chemistry, hydrology and history, and any of those factors could be shaping its fungal residents.

The prokaryotic side of the story unfolded differently. While the bacterial and archaeal communities showed clear taxonomic differences between the two lagoons, the beta-diversity analysis found no statistically significant separation between them at the community level, largely because of substantial variability among samples taken within each lagoon. This contrast between fungi and prokaryotes is one of the study’s most intriguing findings. Two major branches of life, sampled from the same handful of sediments with standard molecular methods, responded in visibly different ways to the same environmental gradient. It suggests that fungal and prokaryotic communities are governed by different ecological rules in these systems, perhaps reflecting differences in dispersal ability, dormancy strategies, or the way each group partitions the sediment environment.

Perhaps the most tantalising result is what the researchers could not identify. A large fraction of the fungal ASVs recovered from the sediments remained taxonomically or functionally unclassified, meaning they did not match any known reference sequence well enough to assign a name or a role. These sediments, it appears, harbour poorly characterised fungal diversity, possibly including lineages new to science or at least new to databases. Inland hypersaline environments are understudied compared with marine and terrestrial habitats, and European examples in particular have rarely been surveyed for fungi with modern molecular methods. Chiprana’s sediments may therefore represent a reservoir of unknown fungal life adapted to some of the saltiest non-marine conditions on the continent.

The broader lesson of the study extends well into the booming world of environmental DNA research. Metabarcoding studies now underpin everything from biodiversity monitoring to climate impact assessments, and most rely on a single marker per organismal group. This work shows that for fungi, ITS1 and ITS2 are not interchangeable windows onto the same community: they recover complementary, partially overlapping views, and conclusions drawn from one may not survive scrutiny with the other. The authors argue that marker choice must be explicitly considered when interpreting metabarcoding-based ecological patterns, and that combining markers, as they did here, offers a more complete picture. For the microbial ecologists charting life in Earth’s extreme environments, the message is clear: before declaring what lives in a hypersaline lagoon, it pays to check which lens you are looking through.

Subject of Research: Fungal and prokaryotic sediment communities in hypersaline and oligohaline lagoons assessed by ITS and 16S rRNA metabarcoding

Article Title: Marker-Dependent Biases and Contrasting Fungal and Prokaryotic Community Patterns in Hypersaline and Oligohaline Lagoons

Article References: Granados-Casas, A. O., Stchigel, A. M., Fernández-Bravo, A., & Cano-Lira, J. F. (2026). Marker-Dependent Biases and Contrasting Fungal and Prokaryotic Community Patterns in Hypersaline and Oligohaline Lagoons. Microbial Ecology. https://doi.org/10.1007/s00248-026-02900-5

Image Credits: AI Generated

DOI: 10.1007/s00248-026-02900-5

Keywords: hypersaline lagoons, fungal ecology, metabarcoding, ITS1, ITS2, 16S rRNA, prokaryotes, salinity, Chiprana, microbial diversity, extremophiles, sediment microbiology

The tool, called SuSha, was created by a team at Nanjing Tech University and is described in a peer-reviewed paper published in the KeAi journal Engineering Microbiology. At its core, SuSha is a machine learning framework designed to predict a microorganism’s salt tolerance from its genetic blueprint alone, without ever requiring the organism to be cultured in a dish. The work addresses a problem that has grown increasingly urgent as metagenomics has transformed microbiology. Modern sequencing technologies allow researchers to reconstruct partial or even near-complete genomes of uncultured microbes directly from environmental DNA samples, generating vast catalogs of genomic data from habitats ranging from ocean water to deep subsurface brines. But a genome sequence on its own says little about how the organism actually lives. Inferring ecological traits, such as salinity preference, from sequence data has remained a stubborn challenge.

Earlier attempts to solve this problem typically relied on the presence or absence of individual genes associated with salt tolerance. Microbes that thrive in salty conditions often carry genes for specialized ion pumps, compatible solute synthesis pathways, and other osmoadaptation mechanisms, and researchers reasoned that detecting such genes could serve as a proxy for salt tolerance. The difficulty, as the SuSha team recognized, is that this single-gene approach frequently fails to capture an organism’s true behavior in complex natural habitats. Salt adaptation is not the product of one gene acting in isolation; it is a systems-level property that emerges from the coordinated action of hundreds of proteins, each of which must remain stable and functional at particular salt concentrations. A microbe might carry a salt-tolerance gene yet be poorly adapted overall, or conversely, might tolerate salt through strategies that a narrow gene screen would miss entirely.

SuSha takes a fundamentally different approach by examining the whole genome through the lens of protein chemistry. The researchers started with a training set of 123 bacterial and archaeal species whose salinity preferences had already been well established through prior study. For each of these organisms, they analyzed the amino acid composition of the encoded proteome, the complete set of proteins the genome specifies. This choice is grounded in evolutionary biochemistry: proteins from salt-loving organisms tend to exhibit distinctive compositional biases, such as an enrichment of acidic amino acids and characteristic patterns in the overall balance of amino acid classes, because their proteins must fold and function properly in briny cytoplasm. From this analysis the team built a 24-dimensional fingerprint for each genome, capturing both the frequencies of individual amino acids and broader chemical properties of the protein complement. The result is a quantitative signature that reflects the evolutionary pressure a lineage has experienced, distilled into a form that machine learning algorithms can interpret.

On top of this fingerprint, the researchers deployed an ensemble learning strategy. Rather than betting on a single algorithm, SuSha combines several machine learning methods, including random forest, bagging, and extra trees, into a single integrated model whose predictions aggregate the strengths of its components. This ensemble approach proved effective. In benchmark testing, SuSha achieved a global accuracy of 0.765 and an area under the receiver operating characteristic curve, or AUC, of 0.941, outperforming any of the individual models on their own. An AUC approaching 0.94 indicates that the framework distinguishes salt-tolerant from salt-sensitive organisms with a high degree of reliability across the full spectrum of salinity preferences, from organisms that prefer near-freshwater conditions to those that flourish in near-saturated brines.

The real test, however, came outside the training data. The team applied SuSha to 2,678 genomes that had been reconstructed from metagenomic samples collected across six regions worldwide, spanning freshwater, marine, and hypersaline habitats. These metagenome-assembled genomes represent uncultured organisms whose lifestyles are largely unknown, making them an ideal proving ground for a tool whose entire purpose is to infer traits without cultivation. The results were striking. In crystallizer ponds, where salinity exceeds 35 percent and only the most extreme halophiles can survive, SuSha correctly identified more than 90 percent of the resident microbes as extreme halophiles. At the opposite end of the spectrum, in the freshwater sediments of Lake Baikal, the world’s deepest lake, the tool accurately flagged salt-sensitive organisms while avoiding false alarms, correctly refraining from labeling freshwater specialists as salt tolerant.

One of the more sophisticated aspects of the framework is that it does not apply a single one-size-fits-all algorithm across all environments. Instead, SuSha switches between strategies depending on the habitat being analyzed. For oceans and freshwater environments, it employs a robust tree-based ensemble, while for near-saturated habitats it uses a linear ensemble. This adaptive design reflects the reality that the genomic signatures of salt adaptation may differ between moderate and extreme salinity regimes, and that prediction methods optimized for one end of the salinity gradient may not perform well at the other. According to Jun Zhou, the study’s corresponding author from the College of Biotechnology and Pharmaceutical Engineering at Nanjing Tech University, the goal was reliability grounded in biology. Crucially, he notes, the tool’s predictions are transparent and traceable back to specific genomic features, which means each result can be tied to real evolutionary signals rather than emerging as an opaque output of a black-box model.

Salinity adaptation is a systems-level trait shaped by the entire genome, not by a single gene, Zhou explains. By reading the amino acid signature of a whole genome, SuSha allows researchers to infer how a microbe that has never been cultured would cope with salt, across the full range from near-freshwater conditions to saturation. This capability has implications that extend well beyond answering an academic question about microbial ecology. Salt-loving microorganisms are a rich source of salt-tolerant enzymes, proteins that remain active and stable in high-salt conditions where conventional enzymes denature or lose function. Such enzymes are valuable in industrial biotechnology, where high-salinity processes are common, and in the treatment of saline wastewater, an increasingly important challenge as industries seek to manage brines generated by desalination, chemical manufacturing, and resource extraction.

The practical promise of SuSha lies in how it reshapes the search for these biotechnological assets. Traditionally, identifying a microbe with useful salt-tolerant enzymes has required laborious screening, growing candidate organisms under varying conditions and testing their enzymatic output, a process Zhou characterizes as blind trial-and-error. With a tool that can scan enormous genomic datasets and pinpoint the most promising organisms first, the search becomes targeted rather than exploratory. Researchers can prioritize which of the thousands of uncultured genomes in public databases deserve the effort of developing new cultivation methods or synthetic biology approaches, dramatically accelerating the pipeline from raw sequence data to industrial application. In an era when genomic databases are doubling at a staggering pace, tools that convert raw sequence information into ecological and functional insight are becoming essential infrastructure for microbiology.

The broader significance of the work lies in what it suggests about the future of studying unculturable life. Most of Earth’s microbial diversity remains inaccessible to classical microbiology, and metagenome-assembled genomes continue to accumulate faster than researchers can characterize them. Frameworks like SuSha demonstrate that meaningful physiological traits can be extracted from genomic sequence alone, provided the underlying biology, in this case the compositional signature that salt stress imprints on proteins, is well understood and translated into appropriate computational features. By grounding its predictions in traceable genomic evidence rather than opaque correlations, SuSha offers a template for building similar tools to predict other hard-to-measure traits, from temperature preference to pH tolerance. For the microbes of the Dead Sea, the solar salt pans, and the countless hypersaline niches in between, the era of invisibility may finally be drawing to a close, one genome at a time.

Subject of Research: Machine learning prediction of microbial salinity adaptation from whole-genome amino acid composition

Article Title: New AI tool predicts how microbes survive in Earth’s saltiest habitats

Article References: New AI tool predicts how microbes survive in Earth’s saltiest habitats. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: halophiles, extremophiles, machine learning, metagenomics, salt tolerance, microbiology, genomics, amino acid composition, ensemble learning, hypersaline environments, biotechnology, Engineering Microbiology

The review, authored by Hussain Alattas, Joseph Boctor, Crystal E. Young, and Daniel V. Murphy of Murdoch University’s Bioplastics Innovation Hub in Australia, together with Sakda Jampasa of Walailak University in Thailand, frames the problem as a translational gap. On paper, extremophiles offer a compelling proposition for environmental biotechnology. Because they are adapted to conditions that suppress most competing life, their extreme niche doubles as a natural barrier against contamination by foreign microbes. That property underpins the tantalizing possibility of open, non-sterile processing, in which waste streams could be treated in unsealed reactors without the costly sterilization steps that conventional bioprocessing demands. The organisms can, in principle, act directly on the very streams that most need treatment, rather than requiring dilution, neutralization, or other pretreatments that drive up cost.

The degradative capabilities documented in the literature are impressive in breadth. Halophilic microorganisms, which flourish at high salt concentrations, have been shown to break down a range of organic pollutants in saline wastewaters where standard activated sludge systems collapse. Acidophiles dominate the chemistry of acidic mine drainage and can mediate the transformation of metals and sulfur compounds. Thermophiles and alkaliphiles extend the operating envelope further, tolerating temperatures and pH values that would denature the enzymes of mesophilic bacteria. The review’s authors acknowledge that this catalog of laboratory demonstrations is, in places, mature. The question they press is deceptively simple: how many of these capabilities have been validated at pilot scale or in the field, under the variable, unforgiving conditions that real industrial sites present?

The answer, they find, is very few. The first and most consequential of six recurring problems is the scarcity of field and pilot validation, a deficit that is especially acute for halophilic systems and for any system involving engineered strains. Most of what is known about extremophile-mediated bioremediation rests on bench-scale experiments conducted in defined media with single contaminants at controlled concentrations. Real waste does not cooperate with such tidy conditions. Industrial effluents arrive as multi-contaminant, multi-stressor matrices, in which salinity, temperature, pH, heavy metals, and mixtures of organic pollutants interact in ways that can amplify or annihilate microbial activity. Whether a strain that degrades a pollutant brilliantly in a flask will do so in a brine laced with competing toxics is, in most cases, an open question.

That uncertainty feeds directly into the second problem the review identifies: performance on real-world matrices, and the unresolved question of whether managed or designed microbial consortia outperform single isolates. In natural environments, pollutant degradation is rarely the work of one organism. Consortia can partition metabolic tasks, exchange metabolites, and buffer one another against stress. Synthetic community design offers a route to engineer these interactions deliberately. But the review notes that the comparative evidence is thin. Few studies have rigorously tested whether a constructed consortium degrades target pollutants faster, more completely, or more stably than the best single isolate, particularly under the fluctuating conditions of actual waste treatment. Until such head-to-head trials exist, the choice between isolate and consortium rests more on intuition than data.

The third problem is perhaps the most striking finding in the review. Per- and polyfluoroalkyl substances, the notorious PFAS family of so-called forever chemicals, have become a global contamination crisis, and microbial defluorination of these compounds remains one of biotechnology’s holy grails. The authors report that in the literature they searched, they identified no reports of halophilic PFAS defluorination at all. This stands in sharp contrast to acidophiles and mesophilic organisms, for which some degradative or defluorinating activity has been documented. The absence matters because PFAS-laden waste is often saline, and fire-fighting foams, landfill leachates, and industrial runoff frequently combine fluorinated chemicals with high salt loads. If halophiles cannot be shown to attack PFAS, an entire category of contaminated brine may lack a biological treatment option. The authors are careful to distinguish genuine absence from underreporting, noting that negative or null results are rarely published, so it remains possible that attempts have been made and simply never reported.

The fourth obstacle is technical rather than ecological: the immaturity of genetic toolkits for extremophiles. The molecular biology revolution that transformed Escherichia coli and other laboratory workhorses into programmable factories has largely bypassed the extreme organisms best suited to harsh waste treatment. Tools for gene editing, heterologous expression, and pathway construction are far less developed for halophiles, thermophiles, and acidophiles than for their mesophilic cousins. This immaturity constrains two things at once. It limits the ability to engineer extremophiles for enhanced degradation of recalcitrant pollutants, and it blocks the development of robust biocontainment strategies, genetic safeguards that would prevent engineered organisms from surviving outside their intended treatment environment. For any regulatory pathway to approve the deliberate release of engineered microbes into open, non-sterile systems, both capabilities would need to advance considerably.

The fifth problem is an opportunity disguised as a gap. The combination of bioremediation with resource recovery, in which the treatment process simultaneously extracts valuable products from the waste stream, has been little explored for extremophile systems. Yet the logic is attractive. Hypersaline brines often contain recoverable magnesium, lithium, or other minerals. Organic waste streams carry chemical energy that microbes can channel into biopolymers or other marketable products. The review’s authors, based at a university bioplastics innovation hub, are well placed to see this potential, and they identify coupling treatment with resource recovery as a promising but unproven route. Demonstrating that an extremophile process can turn a treatment liability into a revenue stream would transform the economics of deployment, but the experiments that would prove the concept have largely not been done.

The sixth and final gap is the one that most often decides whether technology leaves the laboratory: the scarcity of techno-economic and life-cycle evidence. Almost no studies of extremophile-mediated bioremediation include the analyses that investors, regulators, and plant operators actually use to compare options. Without techno-economic assessment, there is no way to know whether an extremophile reactor would be cheaper than physicochemical alternatives such as reverse osmosis or incineration. Without life-cycle assessment, the environmental claims remain unquantified. The review argues that these are not exotic requirements but standard analytical frameworks, and that their absence from the literature reflects a disciplinary habit of stopping at biological proof-of-concept rather than any fundamental barrier to performing the analyses.

What gives the review its force is the discipline with which it separates the genuinely unknown from the merely unreported. For each of the six gaps, the authors specify the experiments and analyses that would close it: pilot-scale trials under real waste matrices, rigorous consortium-versus-isolate comparisons, targeted searches for halophilic PFAS activity, development of genetic and biocontainment tools, integrated treatment-recovery demonstrations, and full economic and environmental accounting. The overall picture is of a field rich in biological capability but poor in translational evidence, poised between an impressive catalog of what extremophiles can do and an almost empty record of what they have actually done at scale. Closing that gap, the authors suggest, is less a matter of discovering new organisms than of doing the less glamorous work of validation, engineering, and economic analysis that turns a capable strain into a deployable process.

Subject of Research: Translational challenges in extremophile-mediated bioremediation of industrial waste streams

Article Title: From capability to deployment: closing the translational gap in extremophile-mediated bioremediation

Article References: Alattas, H., Boctor, J., Young, C. E., Jampasa, S., & Murphy, D. V. (2026). From capability to deployment: closing the translational gap in extremophile-mediated bioremediation. Applied Microbiology and Biotechnology. https://doi.org/10.1007/s00253-026-14068-6

Image Credits: AI Generated

DOI: 10.1007/s00253-026-14068-6

Keywords: extremophiles, bioremediation, halophiles, PFAS, translational gap, environmental biotechnology, resource recovery, microbial consortia, genetic engineering, biocontainment, techno-economic analysis, wastewater treatment

Iron gall ink was the writing medium of Europe from the 12th through the 19th centuries, and its recipe sounds almost alchemical. Scribes mixed iron(II) sulfate with tannin-rich extracts from plant galls and organic binders such as gum arabic. The polyphenols in the tannins react with iron to form dark complexes that deepen to a rich brown-black on exposure to oxygen. The chemistry that made the ink so legible, however, also made it corrosively acidic, and the same reactivity has been slowly eating away at parchment and paper for centuries. In some ancient documents, conservators noticed something stranger still: crystals forming within the ink itself, causing the written text to fade rather than simply darken.

Those crystals turned out to be jarosite, a potassium iron sulfate hydroxide mineral that also occurs in sodium and hydronium varieties. Jarosite precipitation requires a very specific combination of conditions: abundant sulfate, ferric iron, and a strongly acidic environment. Previous attempts to reproduce its formation in laboratory-made inks reached no conclusive explanation, though repeated wetting and drying cycles have long been considered the main trigger. The new study offers a more complete picture, showing that the mineral’s appearance in the manuscript reflects interconnected inorganic and organic processes, including iron redox cycling, organic-iron complexation, and a drop in pH below 3.0, with most of the precipitation chemistry being essentially non-biological.

Under the microscope, the jarosite in the faded manuscript appeared in two telling forms. Dendritic precipitates, branching like miniature frost patterns, marked areas where the mineral had crystallized rapidly from supersaturated solutions. Elsewhere, pseudo-rhombohedral crystals displayed clear evidence of dissolution, their edges etched and corroded. This combination of fresh precipitation and active dissolution is the mineralogical signature of a system in flux, where jarosite forms, breaks down, and re-forms as chemical conditions shift within the ink layer. Crucially, both crystal types were closely associated with fungi and bacteria, placing the microorganisms at the heart of the mineral’s life cycle.

Metagenomic analysis of the ink identified acidophilic fungi belonging to the genera Geotrichum and Coniochaeta as key players. These organisms are extremophiles in a quiet sense, thriving in an environment that would dissolve most organic life. The researchers found that these fungi mobilized elements both inside and outside the inked areas of the manuscript, effectively transporting iron, sulfur, and other components across the document’s surface. In other words, the microbes were not merely passive residents of an acidic niche; they were actively redistributing the ink’s chemistry, driving the dissolution of jarosite crystals and enabling their reprecipitation in new locations.

The mechanism the authors propose is a feedback loop between biology and geochemistry. The ink’s inherent acidity, maintained by residual iron sulfate and the oxidation of iron-tannin complexes, selects for acid-tolerant microorganisms. As fungi and bacteria metabolize the organic binders and interact with the inorganic components, they alter local pH and redox conditions, releasing iron from organic complexes and supplying it to solution. When evaporation concentrates the pore solutions during drying cycles, jarosite precipitates. When humidity rises and conditions shift, the same microbes help dissolve the mineral again, translocating its elements. Each cycle leaves the ink paler and the document more fragile.

This finding reframes a long-standing conservation problem. Ink corrosion has traditionally been treated as a purely chemical threat, managed through deacidification, phytate treatments to complex free iron ions, and strict humidity control. The demonstration that living communities of extremophilic microorganisms participate in the mobilization of iron and sulfate means that microbial management may need to become part of the conservation toolkit. It also explains why laboratory reconstructions of jarosite formation in inks have been inconclusive: without the microbial actors, the full sequence of dissolution, translocation, and reprecipitation cannot be reproduced.

The analytical approach itself is a model for modern heritage science. Micro-Raman spectroscopy allowed the team to identify jarosite and distinguish its potassium, sodium, and hydronium varieties directly on the manuscript without sampling. Scanning electron microscopy paired with energy-dispersive X-ray spectroscopy revealed the crystal morphologies and their elemental signatures, while metagenomics uncovered the taxonomic composition of the microbial community without the need for cultivation, which is essential when the organisms in question are adapted to conditions nearly impossible to replicate on a petri dish. Together, these techniques connected the mineralogical evidence to its biological drivers.

Beyond the archive, the study resonates with research far from the library stacks. Jarosite is a hallmark of acid sulfate environments on Earth, from mine tailings to volcanic hot springs, and its detection on Mars has been interpreted as evidence of ancient acidic water. The Italian manuscript demonstrates that jarosite can form in a human-made, organic-rich microenvironment over historical timescales, provided acidity, iron, and sulfate are available and wetting-drying cycles concentrate the solutions. That a 17th-century scribe’s ink became a natural laboratory for the same geochemistry seen in planetary science is a striking reminder of how universal these processes are.

For the curators and conservators who steward Europe’s documentary heritage, the message is both sobering and actionable. The fading of iron gall ink is not a single chemical event but an ongoing ecological and mineralogical process, one in which acid-loving fungi such as Geotrichum and Coniochaeta and their bacterial companions continuously reshape the ink’s mineralogy. Understanding jarosite precipitation, dissolution, and translocation as coupled biological and inorganic phenomena offers a path toward interventions that address the microbial community as well as the chemistry, potentially slowing the disappearance of texts that have survived centuries of war, humidity, and neglect, only to be threatened by organisms small enough to live inside a single stroke of a pen.

Subject of Research: Microbial colonization of acidic historic iron gall ink and the precipitation, dissolution, and translocation of jarosite

Article Title: Extremophilic microorganisms colonization of acidic historic ink with precipitation, dissolution and translocation of jarosite

Article References: Maisto, F., Pin, L., Pavlović, J., Biocca, P., Bicchieri, M., Cuadros, J., Pangallo, D., & Pinzari, F. (2026). Extremophilic microorganisms colonization of acidic historic ink with precipitation, dissolution and translocation of jarosite. npj Heritage Science. https://doi.org/10.1038/s40494-026-02969-8

Image Credits: AI Generated

DOI: 10.1038/s40494-026-02969-8

Keywords: iron gall ink, jarosite, extremophiles, acidophilic fungi, Geotrichum, Coniochaeta, heritage science, manuscript conservation, micro-Raman spectroscopy, metagenomics, SEM-EDS, mineral dissolution

The research team, led by Sawar Khan and Zanxian Xia of Central South University together with colleagues in China and Pakistan, focused on four families of tardigrade stress-response proteins: SAHS (secretory abundant heat-soluble), CAHS (cytoplasmic abundant heat-soluble), MAHS (mitochondrial abundant heat-soluble), and Dsup (damage suppressor). These proteins, many of them intrinsically disordered, shield cells from dehydration, radiation, and oxidative damage. Until recently, most knowledge about them came from just two well-studied species, Ramazzottius varieornatus and Hypsibius exemplaris. The new study widened the lens to four species, adding Paramacrobiotus metropolitanus and the recently characterized Hypsibius henanensis, using the only four tardigrade genomes with high-quality, well-annotated assemblies available in public databases.

The team’s approach combined several computational techniques. They compared gene structures, mapping exon and intron lengths across species; clustered proteins into orthologous groups using the OrthoMCL algorithm as implemented in OrthoVenn3; built maximum-likelihood phylogenetic trees with IQ-TREE2; identified conserved sequence motifs with the MEME Suite; and predicted three-dimensional protein structures with the AlphaFold Server, anchored by the experimentally solved crystal structure of SAHS1 from R. varieornatus. The result is a multi-layered portrait of how these protein families have diversified, and how their most important features have been preserved, across roughly 100 million years of tardigrade evolution.

The gene copy-number analysis revealed clear species-specific patterns. For the SAHS family, R. varieornatus, H. exemplaris, and P. metropolitanus each carried 13 copies, while H. henanensis had 10. The CAHS family showed even more variation: R. varieornatus had 17 genes, H. exemplaris and P. metropolitanus had 16 each, and H. henanensis had 11. In sharp contrast, the MAHS family was strictly conserved, with exactly one copy in every species examined, a pattern the authors interpret as evidence of strong functional constraint, suggesting that this mitochondrial protective protein performs an essential, possibly irreplaceable role. The Dsup family told yet another story: homologs were found in three species but were conspicuously absent from P. metropolitanus, raising the possibility that this lineage relies on alternative molecular strategies to protect its genome.

Orthologous clustering added nuance to the picture. Of 49 SAHS proteins analyzed, most fell into seven clusters comprising five conserved orthologous groups and two paralogous groups, but nearly a third, 32.65 percent, were singletons found in only one species. The CAHS family showed a similar pattern, with 60 proteins distributed into 13 clusters and 16 singletons, about 26.67 percent of the total. The authors caution that such high singleton counts could reflect lineage-specific adaptation, but they could also stem from technical limits in detecting highly divergent homologs or from gene loss under neutral evolution. Phylogenetic gene trees for both families largely followed the species tree, which the team reconstructed from five conserved single-copy orthologous proteins using the nematode Caenorhabditis elegans as an outgroup, though some individual loci showed discordant placements consistent with gene duplication and lineage-specific evolution.

Perhaps the most consequential discovery was a new member of the Dsup family. Before this study, only two Dsup proteins were known: the original identified in R. varieornatus in 2016, which made headlines when it was shown to boost radiation tolerance in human cultured cells, and a homolog in H. exemplaris. The team identified a third, H.Henanensis.Chr5.66, a 324-amino-acid protein in H. henanensis that they conclude is a likely Dsup ortholog. Pairwise comparisons showed it shares greater similarity with the H. exemplaris protein, a similarity index of 0.60, than with the R. varieornatus protein, at 0.32. Computational predictions placed all three Dsup proteins in the nucleus, with a putative nuclear localization signal near the C-terminus, consistent with their established role in shielding DNA.

What makes the Dsup findings especially intriguing is the contrast between sequence and structure. The three proteins are quite divergent in primary sequence, a pattern the authors attribute to weak selective pressure on an intrinsically disordered protein, similar to what has been observed in late embryogenesis abundant, or LEA, desiccation protectants. Yet structural modeling revealed a conserved α-helical core shared by all three, with pairwise structural superposition yielding root-mean-square deviation values of roughly 3.8 to 4.8 angstroms, indicating moderate fold conservation. All three proteins also displayed a broad central hydrophobic region and a positively charged C-terminal domain, an electrostatic profile well suited to binding nucleosomal DNA. The authors propose that Dsup operates as a flexible molecular shield, stabilizing DNA through electrostatic interactions rather than through a rigid lock-and-key architecture.

The convergence evidence extends to the SAHS and CAHS families as well. Using the ConDor webserver, which detects statistically significant excesses of independent amino-acid substitutions across protein alignments, the team identified candidate convergent sites in both families. In SAHS1, residues E102, H138, and K165 showed significant excesses of independent emergence events, with K165 exhibiting ten independent emergences to lysine and a false discovery rate of 0.00295. In CAHS1, sites S88, E167, and A201 were similarly flagged, with A201 showing seven independent emergences, predominantly to histidine, at an FDR of 0.00215. Critically, when projected onto predicted structural models, all six candidate sites localized within the conserved sequence motifs identified by the team’s motif-discovery analysis, lending biological plausibility to the idea that these recurrent substitutions are functionally relevant rather than stochastic noise.

The authors are careful about the limits of their evidence. All functional inferences in the study are computational and therefore provisional; bioinformatic signals can generate hypotheses but cannot establish molecular mechanism or physiological effect on their own. Computational models also cannot capture cellular context, expression dynamics, post-translational modifications, or the biophysical behaviors that determine protein function in living organisms. The team explicitly frames the reported sites and motifs as prioritized candidates for experimental follow-up, noting that functional assays and comparative evolutionary analyses are needed to definitively establish convergent evolution and to determine whether the recurrent substitutions they identified are truly adaptive.

Even with those caveats, the implications are far-reaching. Tardigrade stress-response proteins are already being explored for applications spanning medicine, agriculture, and space exploration: Dsup has been engineered into human cells, rice, and tobacco pollen to improve radiation tolerance, while CAHS and MAHS proteins show promise for biopreservation, pharmaceutical stabilization, and vaccine storage. By mapping the full diversity of these protein families across tardigrade lineages and pinpointing the residues and structural features under convergent selection, the new study provides a comparative framework that could guide the design of next-generation stress-protective molecules. The water bears, it seems, have not one but several molecular tricks for surviving the unsurvivable, and evolution appears to have found them more than once.

Subject of Research: Convergent evolution of stress-response protein families in tardigrades

Article Title: Integrative bioinformatics analysis of potential convergent evolution in tardigrade stress-response proteins

Article References: Khan, S., Nisar, A., Qadeer, A., Liu, S., Mehmood, S. A., Zhang, L., & Xia, Z. (2026). Integrative bioinformatics analysis of potential convergent evolution in tardigrade stress-response proteins. Stress Biology, 6(1), Article 21. https://doi.org/10.1007/s44154-026-00286-5

Image Credits: AI Generated

DOI: 10.1007/s44154-026-00286-5

Keywords: tardigrades, Dsup, SAHS, CAHS, MAHS, intrinsically disordered proteins, convergent evolution, stress tolerance, bioinformatics, anhydrobiosis, DNA protection, extremophiles

The study was driven by a question at the heart of the emerging circular bioeconomy: can microorganisms with useful traits replace petrochemical and synthetic ingredients in everyday consumer products? Sunscreens are an obvious target. Many conventional UV filters, such as oxybenzone and octinoxate, have come under scrutiny for their environmental persistence and suspected effects on coral reefs and aquatic ecosystems. A biologically produced, biodegradable alternative that can be fermented from renewable feedstocks would fit neatly into the sustainability goals of the cosmetics industry. Mycosporine-like amino acids, the family of compounds to which mycosporine-glutaminol belongs, are already prized in biotechnology because they absorb harmful ultraviolet radiation efficiently while remaining photostable, meaning they do not degrade after repeated exposure to sunlight.

To explore this potential, the researchers isolated and characterized two P. laurentii strains, designated FBU001 from urban São Paulo and FBU003 from the Atacama Desert. Confirming the identity of a yeast strain is not a trivial matter, since misidentified organisms have derailed many biotechnological projects. The team used two complementary approaches: sequencing of ribosomal DNA, the standard molecular barcode for fungal identification, and MALDI-TOF mass spectrometry, a technique that fingerprints the protein profile of a microorganism within minutes. Both methods agreed on the taxonomic assignment, giving the researchers confidence that they were indeed working with P. laurentii and could compare their results against the growing body of literature on this basidiomycetous yeast.

Safety came next, and it is arguably the most consequential part of the work. Any organism proposed for large-scale cultivation must be shown to pose minimal risk to workers, consumers, and the environment. The team assessed biosafety through several independent lines of evidence. They measured the temperature range at which the yeasts can grow, since fungi capable of thriving at mammalian body temperature are inherently more concerning as potential pathogens. They also screened the strains for common fungal virulence factors, the molecular weaponry that pathogenic species use to invade host tissue and evade immune defenses. Finally, they turned to in vivo infection models, experiments in living organisms that provide a direct test of pathogenic potential rather than relying solely on genetic inference. The combined results indicated that both strains have low pathogenic potential, supporting their classification as suitable for industrial applications.

With safety established, the researchers probed the physiological hardiness of the two isolates, and here the contrast between their origins became vivid. Both strains proved resistant to UVC radiation, the shortest and most damaging band of ultraviolet light, which is largely filtered out by the ozone layer but is a formidable stressor for any microorganism that encounters it. The Atacama strain, however, carried additional extremophilic adaptations, most notably tolerance of osmotic stress, the cellular strain imposed by high salt or sugar concentrations that would normally dehydrate and kill less hardy microbes. This makes evolutionary sense: the Atacama Desert subjects its inhabitants to intense solar radiation, extreme aridity, and saline soils, so a yeast surviving there must be a biochemical generalist. The São Paulo strain, adapted to a milder but still sun-exposed urban niche, shared the UVC resistance but not the full suite of desert survival tools.

The centerpiece of the study was the detection and characterization of mycosporine-glutaminol itself. Both yeasts produced the compound, a small molecule that functions simultaneously as a UV filter and an antioxidant, neutralizing the reactive oxygen species that ultraviolet radiation generates inside cells. The researchers then went beyond simple chemical detection and interrogated the genomes and transcriptomes of the two strains. They found that the genes responsible for synthesizing mycosporine-glutaminol are not scattered randomly across the genome but are organized into a cluster, which the team designated the MYC biosynthetic gene cluster. Gene clustering is a hallmark of microbial secondary metabolism and makes both the evolution and the engineering of such pathways more tractable, because the entire production line sits in one contiguous stretch of DNA.

Crucially, transcriptional analyses showed that the MYC cluster is activated by ultraviolet exposure. When the yeasts were irradiated, the genes in the cluster switched on, ramping up production of the protective molecule in response to the threat. This inducible behavior confirms that mycosporine-glutaminol is not an incidental metabolic byproduct but a deliberate, regulated defense strategy. It also suggests a practical advantage for manufacturing: because production is triggered by a simple physical stimulus, UV light, fermentation processes could potentially be tuned to maximize yields without adding expensive chemical inducers. The fact that both the urban and desert strains carry and express the same cluster indicates that this photoprotective capacity is a conserved trait of the species rather than a local adaptation, which broadens the pool of candidate strains available for industrial screening.

The implications extend beyond a single compound. Mycosporine-like amino acids have been investigated for applications ranging from anti-aging skincare, where their antioxidant activity may protect against photoaging, to pharmaceutical formulations that require photostable excipients. A yeast platform that naturally produces one member of this family, and whose biosynthetic genes are mapped and inducible, offers a starting point for metabolic engineering: the MYC cluster could in principle be optimized, transferred to faster-growing production hosts, or modified to generate structural analogs with tailored absorption spectra. The low pathogenicity of the two strains also simplifies the regulatory pathway, since biosafety dossiers for industrial microorganisms demand exactly the kind of evidence this study assembled, from growth-temperature limits to virulence-factor screening to in vivo testing.

The work also carries a broader message about where useful biodiversity hides. A yeast thriving on tree surfaces or soil in a South American megacity and a relative surviving in the hyperarid Atacama turned out to share a sophisticated molecular sunscreen, discovered only because researchers chose to compare strains from contrasting ecological niches. As the cosmetics and chemical industries search for renewable, biodegradable ingredients, extremophilic and urban microorganisms alike are emerging as an underexplored reservoir of functional molecules. For now, the Brazilian team’s two P. laurentii strains stand as robust candidates for sustainable biotechnology, bridging the gap between microbial ecology on two continents and the sunscreen shelf, and offering a glimpse of a future in which the UV protection people wear is grown rather than synthesized.

Subject of Research: Photoprotective compound production by Papiliotrema laurentii yeasts from urban and desert environments

Article Title: Papiliotrema laurentii from two ecological niches: a possible source of next-generation photoprotective compounds

Article References: Santos, R. S., Martins-Silva, G., Barbosa, R. S., da Silva Costa de Oliveira, C. M., Vilanova, P. F., Pereira, P. T., Gianoni, I. M., dos Santos Queiroz, A. C., Padilla, A. A. A., Souza Ramos de Carvalho, A. C., Kreusch, M., Yamaguchi, L. F., Monteiro-Vitorello, C. B., Vallim, M. A., de Medeiros, L. S., & Pascon, R. C. (2026). Papiliotrema laurentii from two ecological niches: a possible source of next-generation photoprotective compounds. Applied Microbiology and Biotechnology. https://doi.org/10.1007/s00253-026-14000-y

Image Credits: AI Generated

DOI: 10.1007/s00253-026-14000-y

Keywords: Papiliotrema laurentii, mycosporine-glutaminol, ultraviolet radiation, sunscreen, Atacama Desert, yeast biotechnology, biosafety, biosynthetic gene cluster, circular bioeconomy, extremophiles, cosmetics, antioxidant

The story begins with the island’s human history. Whalers Bay was home to a whaling station established in the early twentieth century, and its buildings were constructed largely from wood imported from Europe, North America and South America. Later, these structures were repurposed for scientific research operations in the mid-twentieth century. The researchers suspected that this imported timber, along with animal fodder, provisions and other materials brought during the eras of exploitation and exploration, may have inadvertently ferried temperate-zone fungi into Antarctica. Because wood is essentially absent from the natural Antarctic environment, any decomposer fungi found colonizing these historic structures are likely to have arrived with the materials themselves, or to have been attracted to them as nutrient-rich bait for a resident mycobiota already present on the island.

During the Brazilian Antarctic Operation XXXVII in December 2018, the team collected twelve samples of wood, fabric, rope and soil from various points around Whalers Bay. The samples were frozen at minus twenty degrees Celsius during transport back to the Laboratory of Polar Microbiology and Tropical Connections in Brazil. There, the scientists used enrichment cultures of yeast malt medium, incubated at fifteen degrees Celsius, to coax out the cultivable fungi. They also employed a selective medium containing eight percent ethanol to hunt for ethanol-resistant, fermenting yeasts. Colonies were grouped by their macroscopic characteristics, purified, and preserved in the university’s Microorganism and Cell Collection under the code UFMGCB.

Identification relied on a polyphasic approach combining morphology with molecular markers. The researchers amplified the internal transcribed spacer region of ribosomal DNA for filamentous fungi and the D1/D2 domain of the 26S rDNA gene for yeasts, then sequenced the products by the Sanger method and compared them against reference sequences in GenBank using BLASTn, considering isolates with identity of at least ninety-nine percent to be the same species. The results were striking: forty-seven fungal isolates were recovered, representing sixteen genera and twenty-three taxa spanning the phyla Ascomycota and Basidiomycota. The most abundant genus was Coniochaeta, followed by Cadophora, Pseudogymnoascus, Mrakia and Leucosporidium. Other genera included Ascocoryne, Candida, Cystobasidium, Goffeauzyma, Graphium, Mollisia, Naganishia, Papiliotrema, Phenoliferia and Purimyces.

Diversity statistics painted a picture of a rich and highly structured community. The samples yielded a Fisher’s alpha of 17.80, a Margalef richness index of 5.71 and a Simpson’s dominance index of 0.93, indicating high diversity, richness and dominance of decomposer taxa. Crucially, the species accumulation curve generated with the Mao Tao index did not reach an asymptote, meaning the sampling had not exhausted the fungal diversity present in these substrates. This finding mirrors an earlier culture-independent DNA metabarcoding study of the same samples, which likewise revealed cryptic fungal diversity in the historic wooden structures. Together, the two studies reinforce the idea that imported wood acts as both a refuge for introduced species and a magnet for native Antarctic decomposers seeking an abundant organic nutrient source in an otherwise barren landscape.

Many of the genera recovered are familiar players in Antarctic wood decay. Coniochaeta species have been reported from wood on Deception Island and at Japan’s Syowa Station, and from soils in the McMurdo Dry Valleys, though some members of the genus are opportunistic human pathogens. Cadophora luteo-olivaceae, identified in this study, was previously documented in the old buildings at Whalers Bay by Held and Blanchette, underscoring the group’s capacity to thrive in polar environments when wood is available. Pseudogymnoascus is widespread in cold terrestrial and marine environments of both polar regions and is thought to play a central role in decomposition and nutrient cycling. Mrakia, meanwhile, accounts for roughly thirty-five percent of cultivable fungi isolated from lake sediments and soils of East Antarctica, and Leucosporidium species have been found in Antarctic seawater, soils, bryophytes and flowering plants. Even Naganishia, whose members are described as among the most UV-resistant organisms known, made an appearance.

The biotechnological heart of the study lies in the enzymes. All forty-seven isolates were screened for production of four extracellular enzymes: amylase, cellulase, inulinase and pectinase. Activity was assessed by growing the fungi on media containing specific inducing substrates and measuring halos of hydrolysis after seven days at fifteen degrees Celsius, with an Enzyme Index of two or greater defining a good producer. Amylase production was the most widespread, with thirty-five isolates producing degradation halos, followed by inulinase with thirty-four and cellulase with thirty-three, while pectinase lagged at twelve. Inulinase, however, boasted the highest number of good producers, with eight isolates reaching the threshold. Standout performers included Coniochaeta sp. 2, a good producer of both cellulase and inulinase with enzymatic indices of 2.70 and 2.51 respectively, and the yeast Phenoliferia glacialis, which produced cellulase and pectinase with indices of 2.11 and 2.44.

Several of these findings represent firsts for science. The study appears to be the first report of Coniochaeta isolates capable of producing amylase and inulinase, the first report of a Purimyces isolate as a good inulinase producer, and the first documentation of Phenoliferia glacialis producing inulinase. Because all the detected enzymes were active at low temperatures, they carry considerable industrial promise. Cold-active amylases could serve in cold-water detergents, cold saccharification in food processing, textile desizing and animal feed additives for cold climates. Inulinase can generate fructooligosaccharides for functional foods and support cold-fermentation brewing, while pectinase enables fruit juice clarification at low temperatures, preserving vitamins, flavor and color, and finds use in eco-friendly textile bioscouring. Cellulase applications span cold bio-polishing in textiles, cold-wash laundry detergents and environmentally gentler pulp and paper processing. Enzymes that work at low temperatures reduce energy costs, lower the risk of microbial contamination and can eliminate expensive heating equipment entirely.

Perhaps the most commercially intriguing discovery came from the selective ethanol medium. Two isolates of the yeast Solicoccozyma terricola, a psychrotolerant oleaginous species previously known from soils, mosses and lichens in Antarctica and from glacial sediments in Italy, were recovered in low density from wood fragments and soil. Temperature trials showed the yeast grows across a wide range from five to twenty-five degrees Celsius, with the strongest colonies between fifteen and twenty degrees. When cultured in glucose-rich broth at twenty degrees for nine days and stained with the fluorescent dye Nile Red, the cells revealed lipid bodies under confocal microscopy, confirming intracellular lipid production. Previous work by Tasselli and colleagues reported that at twenty degrees this species achieves lipid yields approaching those of palm oil, making it a candidate feedstock for biofuel production, with additional potential in food, cosmetics and textile industries.

The study’s conclusions carry weight beyond biotechnology. The fungal communities documented in Whalers Bay’s lignocellulosic substrates are dominated by decomposers, consistent with the hypothesis that many taxa arrived with imported construction timber, though the authors acknowledge the fungi could also have arrived as spores dispersed by air currents, birds or human activity, or that the imported substrates may simply have acted as bait for fungi already present. Because the surviving buildings form part of a formally declared Antarctic Historic Monument, Antarctic Treaty nations bear a duty to protect these sites, and wood-degrading fungi pose a direct challenge to their long-term conservation. The researchers call for further genetic studies to identify the genes behind the observed enzyme production and detailed investigations of the lipid metabolic pathways in S. terricola. They also emphasize a broader message: the Antarctic ecosystem shelters microbes of great biotechnological potential, reinforcing the urgency of preserving the region against biological loss driven by local climate change. In the frozen timbers of a whaling station, it seems, the continent has been quietly running an experiment in applied biology for over a century.

Subject of Research: Culturable fungal diversity in Antarctic lignocellulosic substrates and their production of cold-active enzymes and lipids with industrial potential

Article Title: Fungal diversity in Antarctic lignocellulosic substrates and their production of enzymes and lipids with potential industrial applications

Article References: Teixeira, E. A. A., de Souza, L. M. D., de Carvalho, C. R., Rosa, C. A., Convey, P., & Rosa, L. H. (2025). Fungal diversity in Antarctic lignocellulosic substrates and their production of enzymes and lipids with potential industrial applications. Blue Biotechnology, 2(1), Article 11. https://doi.org/10.1186/s44315-025-00035-9

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00035-9

Keywords: Antarctica, fungi, extremophiles, cold-active enzymes, bioprospecting, biotechnology, Coniochaeta, Solicoccozyma terricola, oleaginous yeast, biofuel, Deception Island, wood decay

Soap Lake is a meromictic soda lake, meaning its water column is permanently stratified into two layers that never fully mix. The upper mixolimnion, extending to about 19 metres, is relatively warm, brackish and well oxygenated, while the lower monimolimnion, between 21 and 27 metres, is colder, anoxic, hypersaline and contains dissolved sulfide concentrations reported to exceed 150 millimolar. Superimposed on this vertical structure are steep gradients in salinity, redox potential and sulfur chemistry, created by waters enriched in sodium carbonate, bicarbonate and sulfate. These conditions are hostile to most life, yet they have fostered specialised microbial communities, and it is from the sulfidic depths that A. saponilacus was recovered. The lake’s geochemistry even resembles conditions hypothesised for ancient Martian basins and subsurface oceans on icy moons, making it a valuable analogue for astrobiology as well as a reservoir of extremophiles with industrial promise.

A. saponilacus belongs to the family Marinilabiliaceae within the phylum Bacteroidota, a lineage renowned for its sophisticated machinery for degrading complex polysaccharides. The new study began by mapping the bacterium’s metabolic breadth, culturing it anaerobically at 37 degrees Celsius in minimal medium supplemented with a panel of mono- and polysaccharides. The organism grew strongly on beta-glucan substrates, achieving its highest final culture densities on laminarin, a beta-1,3/1,6-glucan from algae, birchwood glucuronoxylan, tamarind xyloglucan and barley mixed-linkage beta-glucan. Growth was minimal or absent on pectin and gum arabic, indicating a lack of the enzymes or transporters needed to exploit those polymers. Among monosaccharides, glucose and xylose supported robust growth, consistent with the bacterium’s preference for glucose- and xylose-based carbohydrates.

To understand how the bacterium targets its preferred substrates, the researchers examined its polysaccharide utilisation loci, or PULs, the genetic systems that Bacteroidetes use to sense, bind and degrade polysaccharides at the cell surface. Genome analysis revealed 14 predicted PULs, four of which appeared tailored to beta-glucans. The team focused on PUL 10, which encodes an unusually rich complement of enzymes, including a glycoside hydrolase family 128 protein, two family 16 enzymes, and auxiliary glycosidases from families 43, 2, 31 and 97 likely involved in removing side-chain decorations. Reverse transcription quantitative PCR confirmed that the SusC/SusD-like transport genes within PUL 10 were strongly upregulated when the bacterium was grown on laminarin but not on xylan, while the equivalent pair from the xylan-targeting PUL 7 responded to xylan but not laminarin. This reciprocal pattern confirmed PUL 10 as the locus specifically dedicated to long-chain beta-glucan degradation.

With beta-glucan metabolism experimentally confirmed, the team mined the bacterium’s published proteome for enzymes with detergent relevance. Modern granular laundry and automatic dishwashing detergents operate at alkaline pH, typically between 9.5 and 11.0, and contain high carbonate and surfactant concentrations that inactivate most enzymes isolated from conventional mesophilic bacteria. Because enzymes secreted by A. saponilacus must function extracellularly in Soap Lake’s carbonate-rich, high-pH waters, the researchers prioritised predicted secreted, endo-acting proteins below 100 kilodaltons. From 3,564 encoded proteins, bioinformatic filtering narrowed the field to 190 enzymatic candidates and finally to a shortlist of 54 for heterologous production, spanning glycoside hydrolases, polysaccharide lyases, lipases, esterases, nucleases and proteases.

Three representative glycoside hydrolases were then expressed recombinantly in Escherichia coli and characterised biochemically in sodium carbonate buffer at pH 10. AsGH16, a multidomain family 16 enzyme carrying three carbohydrate-binding modules and a Por secretion system sorting domain, was confirmed as an endo-beta-1,3-glucanase that cleaves paramylon and yeast beta-glucan into laminaritriose, laminaribiose and glucose, with reduced activity on branched substrates due to steric hindrance. AsGH26, a family 26 enzyme, proved to be an endo-beta-1,4-mannanase active on ivory nut mannan, carob galactomannan and glucomannan. AsGH9, a family 9 enzyme from a separate PUL, showed activity on mixed-linkage lichenan and tamarind xyloglucan, releasing glucose and glucobiose. Notably, AsGH16 retained 60 percent of its activity at pH 9 to 10, and AsGH26 retained a striking 83.8 percent at pH 10, reflecting broadened pH-activity profiles rather than shifted optima, a hallmark of enzymes from environments with fluctuating pH.

AlphaFold3-based structural modelling revealed the molecular basis of this alkaline resilience. All three enzymes displayed an increased prevalence of negatively charged residues on their solvent-accessible surfaces, with folded net charges at pH 10 ranging from minus 7.46 to minus 10.98 per 100 amino acids, a conserved electronegativity thought to stabilise proteins in extreme alkalinity. Beyond surface charge, each enzyme appeared to employ a partially distinct stabilisation strategy. AsGH26 combined the highest hydrogen bond density, 104.7 per 100 residues, with the most tightly packed hydrophobic core and the smallest internal cavity volume. AsGH16 showed the most pronounced lysine depletion, at just 1.7 percent of its mature sequence, suggesting electrostatic strategies and core reinforcement can operate independently. AsGH9, the only enzyme with a disulfide bond, displayed weaker hydrophobic packing and a large internal cavity, consistent with its more neutral pH profile.

The decisive test came through the wash. In automated tergotometer trials mimicking real laundering conditions, each enzyme was spiked at just 2 parts per million into commercial detergents. AsGH16 added to a heavy-duty granular detergent at pH 10.5 delivered a statistically significant 10 percent improvement in make-up stain removal compared with a nil-enzyme control. AsGH26 improved removal of mannan-containing food stains, including chocolate pudding, chocolate ice cream, balsamic salad dressing and guar gum soils, in both heavy-duty liquid detergent at pH 8 and heavy-duty granular detergent at pH 10.5, with significant effects on chocolate stains in both matrices. AsGH9, meanwhile, tackled a different problem: soil redeposition. In multi-cycle washing with particulate carbon black, cotton fabrics washed with AsGH9 retained a whiteness index of minus 32.0, against minus 58.8 for detergent alone, a visible and quantifiable preservation of fabric whiteness across repeated washes.

Enzymes have already revolutionised laundering by enabling effective cleaning at lower temperatures, reducing energy demand and fossil fuel use. Yet the extreme alkalinity of modern detergent matrices has long limited which biocatalysts can be deployed, since most commercial enzymes derive from mesophilic organisms. Previous alkaliphilic cellulase producers, such as Bacillus strains KSM-19, KSM-64 and KSM-520, have been exploited for detergents but remain largely confined to cellulase activity. In contrast, A. saponilacus combines metabolic versatility across multiple complex carbon sources with a diverse repertoire of more than 50 predicted secreted enzymes, positioning it not only for detergent applications but potentially also for paper pulping, lignocellulosic biomass deconstruction and the treatment of alkaline industrial effluents, all processes where robust activity at high pH is prized.

The study’s authors conclude that Alkalitalea saponilacus stands as an excellent natural source of alkaline-stable, detergent-compatible enzymes, validated at every level from genome and gene expression through protein structure to in-wash performance. The compatibility of AsGH9, AsGH16 and AsGH26 with the surfactants, builders and carbonate concentrations of real formulations, together with their broad functional pH ranges, suggests these soda lake adaptations could soon find their way from one of Earth’s harshest aquatic environments into the washing machines of everyday consumers, while deeper exploration of the world’s soda lakes may yield further extremophilic catalysts waiting to be discovered.

Subject of Research: Alkaline-tolerant glycoside hydrolases from the soda lake bacterium Alkalitalea saponilacus with detergent biotechnology applications

Article Title: Exploration of Alkaliphilic Bacteria Alkalitalea saponilacus Identifies Glycoside Hydrolases With Biotechnological Potential

Article References: Stephen, A., Brown, N. L., Rostron, R., Wigham, R. J., Malekpour, A. K., Black, G. W., Garcia, A. L. M., Yau, H. C. L., Lant, N. J., & Munoz‐Munoz, J. (2026). Exploration of Alkaliphilic Bacteria Alkalitalea saponilacus Identifies Glycoside Hydrolases With Biotechnological Potential. Microbial Biotechnology, 19(9), Article e70448. https://doi.org/10.1111/1751-7915.70448

Image Credits: AI Generated

DOI: 10.1111/1751-7915.70448

Keywords: Alkalitalea saponilacus, soda lakes, Soap Lake, extremophiles, glycoside hydrolases, CAZymes, alkaliphilic bacteria, detergent enzymes, polysaccharide utilisation loci, biotechnology, stain removal, protein stability

A research team led by Professor Gaku Fukuhara of Kyushu University’s Institute for Materials Chemistry and Engineering set out to understand this adaptation at the molecular level. Their work, published in Scientific Reports, centers on a protein called PoXeR, a light-driven molecule taken from a bacterium that lives in the deep ocean. Using a custom-built apparatus capable of applying precisely controlled hydrostatic pressure, the researchers watched what happened to the protein’s structure as the pressure climbed from everyday conditions to levels equivalent to the deepest point of Earth’s oceans. What they found was a remarkable self-assembly strategy that allows the protein to reinforce itself exactly when the environment threatens to break it apart.

The protein belongs to a family known as microbial rhodopsins, light-activated proteins that microorganisms use to capture energy from photons. These molecules have been studied extensively under ordinary laboratory conditions, but their counterparts from extreme environments have remained largely mysterious. To isolate what makes the deep-sea version special, the team compared it directly with a relative from a very different world. PoXeR, short for Parvularcula oceani xenorhodopsin, comes from a deep-sea bacterium adapted to high-pressure living. Its counterpart, Gloeobacter rhodopsin, or GR, comes from a terrestrial bacterium that spends its entire life at atmospheric pressure. If pressure tolerance were written into the structure of these proteins, a side-by-side comparison should reveal it.

The experimental design was as ambitious as the question. Researchers at the Institute for Solid State Physics of the University of Tokyo prepared the protein samples, while colleagues at the Department of Chemistry of the Institute of Science Tokyo carried out the pressure experiments. Using their custom apparatus, the team subjected both proteins to hydrostatic pressures ranging from 0.1 megapascals, the pressure at sea level, up to 120 megapascals, which corresponds to the crushing conditions found at the bottom of the Mariana Trench. Throughout the compression cycle, spectroscopic techniques tracked how the proteins interacted with light, providing a sensitive readout of structural integrity, because a rhodopsin’s light-absorption spectrum changes when its molecular architecture is disturbed.

The contrast between the two proteins was striking. When Gloeobacter rhodopsin was pressurized, its structure became unstable and the protein essentially denatured, losing the folded shape that gives it function. Worse, the damage was permanent. When the pressure was released, the protein’s absorption spectrum did not return to its original state, indicating that it had undergone irreversible structural changes. The terrestrial protein, in other words, had no defense against the deep-sea environment. Its molecular architecture, perfectly adequate for life on land, simply could not cope with the mechanical stress of extreme hydrostatic pressure.

PoXeR told a completely different story. As the pressure mounted, the deep-sea protein adapted rather than collapsed, maintaining a stable structure throughout the entire range tested. When the researchers released the pressure, its absorption spectrum returned almost entirely to its original state, with no visible signs of denaturation. The protein had endured conditions equivalent to the deepest ocean floor and emerged essentially unscathed. The results demonstrate that PoXeR possesses dramatically greater structural stability than its terrestrial cousin, and that this stability is not a passive property but an active response to the environment.

The key to that resilience, the researchers discovered, lies in a process called oligomerization-mediated structural stabilization. As pressure increases, individual PoXeR molecules respond by assembling themselves into groups of three, forming what is known as a trimeric structure. This three-unit arrangement is highly suited to the extreme conditions of the deep sea, effectively allowing the protein to reinforce itself under stress. Fukuhara explains that the molecules adapt to the high-pressure environment by forming these trimers, and that this is how PoXeR remains stable under pressure. Rather than resisting the force of the deep ocean through rigid construction alone, the protein uses the pressure itself as a trigger to build a more robust configuration.

For Fukuhara, the motivation behind the study was fundamental curiosity about one of biology’s enduring puzzles. For a long time, he notes, no one really understood how organisms adapted to the extreme conditions of the deep sea, and understanding that adaptation at the molecular level drove the research. The findings now offer a concrete mechanism, showing that pressure tolerance can emerge from a dynamic structural strategy rather than from a single rigid molecular design. This principle may well apply beyond rhodopsins, suggesting that other deep-sea proteins could employ similar pressure-triggered assembly to protect their structures in the hadal zones of the ocean.

The implications extend well beyond marine biology. Because microbial rhodopsins are light-driven proteins, they are attractive building blocks for engineered materials that respond to light. Understanding how PoXeR maintains its function under extreme pressure could guide the development of light-responsive protein materials capable of operating in harsh environments, from industrial bioreactors to deep-sea sensors. A protein that can survive 120 megapascals and recover its function afterward is an unusually durable component, and durability of exactly this kind is what engineers need when designing molecular machines for conditions that would destroy conventional materials.

The team is already looking toward applications in medicine. Fukuhara says the next step is to move into the medical field, where the researchers want to understand how the human body responds to increasing hydrostatic pressure and how this might affect the development and treatment of cancer and other diseases. The connection is less far-fetched than it might seem, since hydrostatic pressure influences biological processes in contexts ranging from diving physiology to high-pressure medical treatments. By revealing a molecular mechanism that cells can use to sense and survive pressure, the deep-sea protein PoXeR may ultimately teach researchers something about pressure responses in human cells as well, turning a curiosity about life at the bottom of the ocean into insights with potentially far-reaching clinical value.

Subject of Research: Molecular adaptation of the deep-sea microbial rhodopsin PoXeR to high hydrostatic pressure

Article Title: Under pressure: How a deep-sea protein adapts to an extreme environment

Article References: Under pressure: How a deep-sea protein adapts to an extreme environment. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: deep sea, PoXeR, microbial rhodopsin, hydrostatic pressure, protein stability, oligomerization, trimeric structure, Kyushu University, spectroscopy, xenorhodopsin, extremophiles, Scientific Reports