The research team, led by Abdulwasid Abubakari and Charity Ahiabor of Accra Technical University in Ghana, together with George Osei-Adjei and corresponding author Hizbullah Khan of Guangdong Medical University in China, assembled and analyzed 467 high-quality P. aeruginosa genome assemblies. Every genome included in the analysis met a strict quality threshold of greater than 95 percent completeness, and the collection spanned 17 African countries over a remarkable 26-year window, from 1998 to 2024. All of the data were drawn from publicly available assemblies in the NCBI database, meaning the study required no new sampling or ethics approvals, but its systematic reanalysis with standardized tools allowed comparisons that had previously been impossible across such a geographically and temporally scattered dataset.

The methodological backbone of the study was a pangenome analysis, an approach that partitions the collective gene repertoire of a bacterial species into the core genome shared by all isolates and the accessory genome carried by only some. The researchers used iterative pangenome clustering across seven amino acid identity thresholds ranging from 50 to 98 percent, a strategy that captures gene families at different levels of evolutionary relatedness. They complemented this with exploratory core-genome single nucleotide polymorphism phylogenetics to reconstruct the evolutionary relationships among isolates, and with pangenome-wide association studies, or Pan-GWAS, to detect accessory genes whose presence correlates with specific geographic regions.

The results revealed an exceptionally “open” pangenome architecture, quantified by a scaling exponent of gamma equal to 0.23. In pangenome mathematics, a low gamma value signals that each newly sequenced genome is likely to bring a substantial number of previously unseen genes into the catalogue, indicating enormous genetic diversity and extensive gene acquisition. Across the African population, the analysis catalogued 25,501 distinct gene families, a figure that underscores how genetically versatile this pathogen is on the continent. An open pangenome also has practical implications for surveillance: it suggests that local African isolates may carry functional repertoires that global reference-based analyses routinely miss, and that continued sampling will keep yielding new genetic material rather than approaching a saturation point.

Phylogenomic reconstruction resolved 466 unique core genome SNP profiles, and the resulting tree was characterized by strong regional clustering. In other words, isolates from the same part of the continent tended to be more closely related to each other than to isolates from distant regions, a pattern consistent with largely local transmission and evolution rather than a single continental epidemic lineage sweeping across borders. This regional structure matters for public health planning, because it implies that resistance control strategies may need to be tailored to regional population dynamics rather than applied as one uniform continental blueprint.

Perhaps the most striking finding is what the authors describe as an “African Clonal Inversion.” Globally, the sequence type known as ST235 is regarded as the archetypal P. aeruginosa super-clone, a multidrug-resistant lineage that has spread through hospitals worldwide and dominates high-risk clone surveys on other continents. In the African dataset, however, the picture is reversed. Among the 71 isolates identified as belonging to high-risk clones, ST111 accounted for 46.5 percent, or 33 of 71 isolates, outnumbering ST235, which represented 14.1 percent or 10 of 71, by more than three-fold. This inversion suggests that the forces shaping P. aeruginosa success in African healthcare settings differ from those driving the global spread of ST235, and it raises the possibility that ST111 possesses ecological or resistance advantages that are particularly effective in African hospital environments.

The study also mapped the resistome, the complete set of antimicrobial resistance genes carried by the isolates, and found it to be geographically stratified in a way that has direct clinical consequences. The gene blaNDM-1, which encodes the New Delhi metallo-beta-lactamase and confers resistance to some of the most powerful last-line carbapenem antibiotics, dominated in Northern and Eastern African country subsets. Meanwhile, blaVIM-2, another metallo-beta-lactamase gene but from a distinct enzymatic family, was concentrated in Southern Africa. Because both genes threaten the carbapenem class that clinicians rely on when treating severe P. aeruginosa infections, their uneven continental distribution means that empirical treatment guidelines and diagnostic panels may need to account for which resistance determinants are actually circulating in a given region rather than assuming a homogeneous African resistance landscape.

Beyond resistance genes, the Pan-GWAS analysis uncovered regional associations in the accessory genome that hint at how local P. aeruginosa populations differ in their broader functional biology. The researchers found enrichment of a Type VI Secretion System component, the tla3 gene, in North African isolates. The Type VI Secretion System is a molecular spear-like apparatus that bacteria use to inject effector proteins into competing microbes and host cells, playing a major role in interbacterial competition and virulence. In West Africa, the analysis identified enrichment of phenazine biosynthesis clusters, including the phzA2 gene. Phenazines are redox-active secondary metabolites that contribute to P. aeruginosa’s survival, biofilm formation and pathogenicity. These regional functional signatures suggest that different African populations may have evolved distinct ecological strategies, potentially shaped by local hospital conditions, antibiotic prescribing practices, microbial competition and environmental reservoirs.

To make these findings actionable rather than merely archival, the team integrated the entire dataset into a live interactive dashboard hosted on Microreact, a widely used platform for visualizing genomic epidemiology. This means that researchers, public health officials and clinicians across Africa and beyond can explore the phylogenetic trees, geographic distributions and resistance gene patterns themselves, updating the picture as new genomes are deposited. Such open infrastructure is particularly valuable on a continent where surveillance capacity varies widely between countries, because it lowers the technical barrier for local laboratories to place their own isolates in continental and global context.

The study’s authors are careful to frame their work as a foundation rather than a finished map. The dataset, while the largest of its kind for the continent, still reflects the uneven distribution of sequencing capacity and data deposition across Africa, and the researchers themselves categorized some countries with limited sampling as yielding only exploratory Pan-GWAS results. Nevertheless, by demonstrating that African P. aeruginosa populations have their own clonal hierarchy, their own resistance geography and their own accessory gene signatures, the analysis makes a compelling case that the continent can no longer be treated as a footnote in global pathogen genomics. As antimicrobial resistance continues to escalate worldwide, understanding how Priority 1 pathogens evolve in undermapped regions is not just an African concern but a global one, and this study provides both the evidence and the tools to begin that work in earnest.

Subject of Research: Pan-African genomic population structure and antimicrobial resistance distribution of Pseudomonas aeruginosa

Article Title: Pan-African genomics of Pseudomonas aeruginosa highlights regional population structure and AMR stratification

Article References: Abubakari, A., Ahiabor, C., Osei-Adjei, G., & Khan, H. (2026). Pan-African genomics of Pseudomonas aeruginosa highlights regional population structure and AMR stratification. BMC Genomics. https://doi.org/10.1186/s12864-026-13365-8

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13365-8

Keywords: Pseudomonas aeruginosa, pangenomics, antimicrobial resistance, Africa, genomic epidemiology, high-risk clones, resistome, ST111, ST235, Pan-GWAS, MLST, BMC Genomics

The motivation behind the work lies in the convergence of two technological currents. Graph pangenomics and long-read sequencing, the authors argue, together hold the promise of integrating read mapping directly with variant calling. A single long read, spanning thousands of DNA letters in one continuous stretch, can provide strong evidence not only for single nucleotide variants but also for larger or more complex structural variations that are notoriously difficult to detect with short reads. Short-read sequencers chop the genome into fragments of a few hundred bases, and when a structural variant spans a region longer than a single fragment, the evidence is scattered and easily missed. Long reads, by contrast, can traverse an entire rearranged segment, carrying the signal for the variant within one molecule. To fully realize this potential, however, the classical algorithms used to align sequences against graphs must be extended to account for recombination events among haplotypes, all while maintaining the practical efficiency that large-scale sequencing projects demand.

Recombination is not a rare curiosity in genome biology; it is a fundamental force that reshapes chromosomes in every generation. When a read originates from a haplotype that inherited one segment from one ancestral path through the pangenome and an adjacent segment from another, an aligner that insists on a single coherent path through the graph will either misalign the read or miss the true origin altogether. Capturing such events formally is what the authors call the R-bounded Recombination-Aware Alignment Problem, abbreviated R-RAAP in the paper. The task is to find the best alignment of a query sequence to a path through a variation graph while allowing a bounded number of recombinations, that is, switches between distinct haplotype paths embedded in the graph. Solving this problem exactly with classical dynamic programming quickly becomes intractable as the number of allowed recombinations grows, because the search space of possible path combinations explodes combinatorially.

The team’s answer to this computational wall is an algorithmic strategy borrowed from artificial intelligence: the A* search framework. A* is a best-first search method that explores a space of possible solutions by prioritizing states that look most promising according to a heuristic function, an estimate of the remaining cost to reach a goal. When the heuristic is admissible, meaning it never overestimates the true remaining cost, A* is guaranteed to find an optimal solution while typically examining only a small fraction of the full search space. RecAlign applies this idea to sequence-to-graph alignment, steering the search through the variation graph toward the alignments that are most likely to be optimal and pruning away the vast regions of the search space that cannot contribute to the best answer. The result, according to the study, is an aligner that is both accurate and fast, and that can efficiently manage two or more recombination events when aligning a read against a variation graph.

The theoretical underpinnings of the work draw on a rich toolkit of combinatorial algorithms and data structures. The abbreviations section of the paper alone signals the depth of the machinery involved: dynamic programming, the longest increasing subsequence problem, the Ferragina-Manzini index better known as the FM-index, and the directed acyclic graph structure that underlies most variation graph representations. The authors also invoke the Strong Exponential Time Hypothesis, a central conjecture in computational complexity theory, which suggests that the recombination-aware alignment problem is unlikely to admit dramatically faster exact algorithms in the worst case. This complexity barrier makes the heuristic-guided pruning of A* not merely a convenience but a necessity: without a way to focus the search, exact recombination-aware alignment would remain confined to toy examples rather than chromosome-scale graphs.

Efficiency alone would not matter if the tool could not be deployed in realistic pipelines. A key contribution of the study is the integration of RecAlign into a chain-and-extend framework, an architectural pattern familiar from classical read aligners, in which short high-confidence matches are first chained together into larger anchors and the alignment is then extended around those anchors. Within this framework, the authors report that RecAlign is currently the only recombination-aware tool that can be used in practice to align long reads against chromosome-wide pangenome graphs. That distinction matters because chromosome-wide graphs, such as those built from the collections of haplotypes assembled by the Human Pangenome Reference Consortium, are precisely the scale at which modern pangenome analyses operate. Tools that can only handle gene-sized or region-sized graphs, however accurate, cannot serve as the mapping engine for whole-genome sequencing experiments.

The biological payoff of recombination-aware alignment is expected to be greatest in the most complex and clinically important regions of the genome. The paper’s list of abbreviations points to the human leukocyte antigen region and the major histocompatibility complex, the hyper-polymorphic immune loci where haplotype diversity is extreme and where short-read mapping has historically struggled most. It also references non-allelic homologous recombination, the mutational mechanism behind many recurrent structural variants, and the Graphical Fragment Assembly and Graph Alignment Format standards that allow graph-based results to flow between tools. By explicitly modeling recombinations among the haplotypes embedded in a variation graph, RecAlign can in principle place reads onto the correct combination of ancestral paths, sharpening downstream variant calling in regions where a linear reference would systematically mislead.

The work did not emerge in isolation. The authors acknowledge helpful discussions with Davide Cozzi and Simone Ciccolella during the development of the project, and the research was carried out within a substantial European funding framework. Monti, Riccardi, Della Vedova, Rizzi and Bonizzoni received support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement PANGAIA, number 872539, a network dedicated to pangenome algorithms and data structures. The work was further supported by the Horizon Europe programme under project FORGENOM II, identifier 101160008, and partially by the Italian Ministry of University and Research through the Dipartimenti di Eccellenza 2023-2027 grant of the Department of Informatics, Systems and Communication at the University of Milano-Bicocca. Bonizzoni, Della Vedova and Rizzi contributed equally to the study, reflecting a collaboration that spans algorithmic theory and practical bioinformatics engineering.

Consistent with the norms of the field, the implementation is open source and freely available on GitHub under the AlgoLab organization, in the RecGraph repository on the a_star branch, allowing other developers to inspect, reuse and extend the code. The authors declare no competing interests, and all data used in the study were either taken from public repositories or simulated, so no new human subject data were generated. The article is published open access under a Creative Commons Attribution 4.0 International license and was released as a citable, peer-reviewed accepted manuscript with a permanent DOI, subject to further editorial production before the final version of record.

For the broader genomics community, RecAlign represents a step toward a long-standing goal: mapping reads in a way that respects the true evolutionary structure of the population from which they came. As pangenome references grow to encompass ever more diverse haplotypes, and as long-read sequencing becomes routine in clinical and research settings, the algorithms that connect these technologies will determine how much of the genome’s complexity can actually be read out of the data. By showing that recombination-aware alignment can be made fast enough for chromosome-wide graphs, the Milano-Bicocca and UC Santa Cruz team has removed one of the practical obstacles standing between graph pangenomics and its everyday use, and has provided a concrete, tested tool that other groups can now build upon.

Subject of Research: Recombination-aware sequence-to-graph alignment for pangenome read mapping

Article Title: Faster and accurate recombination-aware sequence-to-graph aligner

Article References: Monti, D. C., Riccardi, B., Sirén, J., Bonizzoni, P., Della Vedova, G., & Rizzi, R. (2026). Faster and accurate recombination-aware sequence-to-graph aligner. BMC Bioinformatics. https://doi.org/10.1186/s12859-026-06640-8

Image Credits: AI Generated

DOI: 10.1186/s12859-026-06640-8

Keywords: pangenomics, variation graphs, sequence-to-graph alignment, long-read sequencing, recombination, A* search, RecAlign, BMC Bioinformatics, variant calling, FM-index, Human Pangenome Reference Consortium, computational biology

The pivotal discovery is that crystalline nanorod formation is not an intrinsic enzymatic property of the bacterium itself but an emergent property of its biofilm. In a carefully designed three-state experiment, the researchers exposed biofilm-associated cells, free-swimming planktonic cells, and cells stripped of their extracellular polymeric substance (EPS) matrix to 2 millimolar sodium selenite under identical conditions. Only the intact biofilms produced precipitates ranging from dark red to metallic grey, the classic visual signature of the amorphous-to-trigonal transition. X-ray diffraction confirmed the observation with striking clarity: biofilm-derived samples displayed sharp, well-resolved reflections at 2-theta values of approximately 23.5, 29.7, and 43.6 degrees, assigned to the (100), (011), and (110) crystallographic planes of trigonal selenium. The planktonic condition showed only weak trigonal signals superimposed on dominant amorphous scattering, while the EPS-depleted condition produced essentially no detectable crystalline phase at all. Because all three states retained the metabolic capacity to reduce selenite, the conclusion is unambiguous: the EPS matrix is required to direct the structural form of the reduction product, not the reduction itself.

The speed of the transformation makes the finding even more remarkable. Thermal annealing of amorphous selenium into the trigonal phase normally requires temperatures above 100 degrees Celsius sustained over hours to days. The biofilm condition achieved sharp, intense trigonal diffraction patterns after just 168 hours at 28 degrees Celsius with no thermal treatment whatsoever, implying that the EPS matrix substantially lowers the kinetic barrier to trigonal nucleation and effectively functions as a crystallization catalyst operating at ambient temperature. This is, according to the authors, the first reported demonstration of ambient-temperature, EPS-driven crystallization of trigonal selenium by a bacterial biofilm system, mechanistically distinct from all previously described thermally driven recrystallization routes.

High-resolution imaging and electron diffraction added atomic-scale confirmation. HAADF-STEM microscopy revealed that biofilm-associated cells generate a high density of elongated nanostructures, 250 to 500 nanometres in length, distributed mainly in the extracellular space surrounding cell clusters. Selected-area electron diffraction of individual nanorods produced discrete diffraction spots rather than diffuse rings, indicating single-crystal or highly textured material indexed to the (101) and (111) planes of trigonal selenium. Critically, the (100) reflection, which corresponds to the lateral facets of the helical selenium chain axis, was detected exclusively in biofilm-derived nanorods. In the trigonal selenium crystal system, helical chains run parallel to the c-axis, the natural elongation direction of the crystal. The exclusive presence of this reflection in the biofilm condition indicates that nanorod elongation occurs with a high degree of orientational order and requires the organized template that only an intact EPS matrix provides. Planktonic and EPS-depleted particles, lacking this template, remained isotropic and randomly oriented, explaining their spherical morphology.

Fourier-transform infrared spectroscopy illuminated the molecular interactions underlying this templating. Exposure to selenite produced pronounced shifts in the amide I and amide II bands of EPS-associated proteins, indicating conformational changes consistent with selenium coordination to amino acid side chains, particularly cysteine thiols and lysine amines. Perturbations in the polysaccharide-dominated regions, including carboxylate and hydroxyl stretching frequencies, pointed to direct electrostatic coordination of selenite oxyanions to these metal-binding functional groups. The researchers propose a division of labour within the matrix: polysaccharide components capture and concentrate selenium ions, while proteinaceous components, notably flagellin filaments, provide the structural axis that imposes crystallographic directionality on nucleation and elongation. Flagellin from other bacteria has previously been shown to template one-dimensional silica nanotubes and gold surfaces, lending independent plausibility to this model.

But an intact biofilm is only useful if it survives the very conditions it is meant to remediate. Heavy metals such as nickel, cadmium, and copper are known to suppress biofilm formation in most bacteria by disrupting quorum-sensing signalling, the chemical communication system that coordinates EPS production. Here BII-R7 revealed a second extraordinary trait. While comparator strains suffered biofilm reductions of 60 to 84 percent under metal stress, BII-R7’s biofilm biomass actually increased by nearly 22 percent in the presence of 2 millimolar nickel, a metal-stimulated enhancement that runs counter to the general trend among environmental isolates. Comparative gene screening supplied a genomic explanation: BII-R7 is the only strain in the comparison that lacks both rpfF and smoR, the two central regulators of the Stenotrophomonas diffusible signal factor quorum-sensing system. By bypassing the signalling pathway that metals sabotage, BII-R7 maintains its EPS-producing biofilm precisely where other organisms lose it, preserving the scaffold on which crystalline nanorod formation depends.

To probe the deeper genetic basis of this dual capacity, the team re-sequenced the BII-R7 genome, producing a far higher-quality assembly than the previous draft, and compared it against 37 other Stenotrophomonas genomes. The pangenome analysis revealed an open structure with a small core genome of just 670 genes and an expansive cloud genome of over 21,500 gene clusters, a signature of frequent horizontal gene transfer. BII-R7 stood out dramatically, harbouring more than 2,300 genes found in no other strain, many showing sequence homology with diverse soil and aquatic bacteria, consistent with long-term residence in geochemically complex clay formations. Among these exclusive genes, the researchers identified a suite of metal resistance determinants absent from every comparator: copF and copB encoding dual copper efflux mechanisms, czcA for broad-spectrum divalent cation extrusion, a NodT-family RND efflux lipoprotein, and an exclusive molybdate ABC transporter that supports the molybdenum-dependent enzymatic pathway implicated in selenium oxyanion reduction.

Functional validation confirmed that these genomic predictions translate into real phenotypes. Under copper stress, BII-R7 maintained growth comparable to untreated controls at 2 millimolar copper, while all three comparator strains showed roughly 50 percent growth suppression. Quantitative real-time PCR demonstrated that the exclusive resistance genes are actively transcribed and metal-responsive: copF was induced 8.6-fold and copB 3.4-fold under copper stress, while czcA surged 42.2-fold under nickel stress. Two exclusive EPS-remodelling proteins emerged as the strongest candidates for the nanorod-templating phenotype itself. The first, a Wzy-family polysaccharide ligase, possesses a divergent extracellular loop enriched in twelve acidic residues, three histidines, and two cysteines, established ligands for selenium oxyanions, predicted to generate a polysaccharide scaffold with a charge distribution and metal-coordination geometry unlike any other strain. The second, a secreted GH92-family alpha-mannosidase that is transcriptionally induced under selenium stress, is predicted to trim mannosyl branches from the maturing matrix, linearizing EPS fibrils into parallel nano-channels of uniform geometry ideal for templating anisotropic crystal growth.

The authors are careful to frame their genomic framework as hypothesis-generating rather than definitively causal, noting that targeted knockout and complementation experiments are the immediate next step, alongside biochemical characterization of the EPS itself and quantitative crystallography of nanorod yields. Even so, the practical implications are considerable. In bioremediation, trigonal nanorods settle and filter far more efficiently than amorphous nanospheres, improving the operational performance of bioreactor systems treating mining drainage and industrial effluents. Previous work has already demonstrated up to 70 percent selenite removal from contaminated water using BII-R7 immobilized in alginate hydrogels, and promoting biofilm development within such matrices is predicted to enhance removal further while enabling recovery of crystalline product. In green nanotechnology, the biofilm route offers a scalable, low-energy alternative to conventional synthesis that demands high temperatures, toxic reductants, or organic solvents. Crystalline selenium nanostructures also show superior antitumoral and antimicrobial activity relative to their amorphous counterparts. With its non-pathogenic status, exclusive genetic toolkit, and demonstrated compatibility with immobilization formats, BII-R7 offers a coherent blueprint: preserve the biofilm, and the biofilm builds the crystal.

Subject of Research: EPS-templated biosynthesis of crystalline selenium nanorods and multimetal resistance in Stenotrophomonas bentonitica BII-R7

Article Title: Genomic Insights Into the Multimetal Resilience and Biofilm‐Templated Nanorod Biosynthesis of Stenotrophomonas bentonitica BII‐R7: Bioremediation and Green Nanotechnology Implications

Article References: Perez‐Muelas, E., Ruiz‐Fresneda, M. A., Lazuen‐Lopez, G., Lopez‐Perez, T., Eddaoudi‐Lakraichi, F., Bakkali, M., & Merroun, M. L. (2026). Genomic Insights Into the Multimetal Resilience and Biofilm‐Templated Nanorod Biosynthesis of Stenotrophomonas bentonitica BII‐R7: Bioremediation and Green Nanotechnology Implications. Microbial Biotechnology, 19(9), Article e70422. https://doi.org/10.1111/1751-7915.70422

Image Credits: AI Generated

DOI: 10.1111/1751-7915.70422

Keywords: Stenotrophomonas bentonitica, selenium nanoparticles, bioremediation, biofilm, extracellular polymeric substances, pangenomics, green nanotechnology, heavy metal resistance, trigonal selenium, horizontal gene transfer, quorum sensing, biomineralization