Microorganisms have evolved a remarkably diverse arsenal of defenses against metal-induced stress. Some sequester metal ions intracellularly, binding them tightly so they cannot interfere with sensitive biochemical processes. Others transform metals enzymatically into less toxic chemical forms, pump them back out of the cell through dedicated efflux systems, or immobilize them on the cell surface, preventing entry in the first place. Among the most intriguing of these defenses are the metallothioneins, a family of small, cysteine-rich proteins capable of binding metal ions with extraordinarily high affinity. Their abundant thiol groups act as molecular sponges, mopping up free metal ions and contributing to cellular detoxification. Metallothioneins have been studied extensively in eukaryotes, where they are found across animals, plants, and fungi, but bacterial examples remain comparatively rare and poorly characterized, with most known cases confined to cyanobacteria and a handful of other species.

That gap in knowledge is precisely what a team of Italian researchers set out to address. In a study published in Applied Microbiology and Biotechnology, Annamaria Vitiello of the University of Naples Federico II, Emilia Pedone of the Institute of Biostructures and Bioimaging at Italy’s National Research Council, Danila Limauro, and their colleagues report the identification and characterization of a novel hybrid protein from the bacterium Runella aurantiaca. The protein, which they named TrxA, is a genuine molecular chimera: it fuses a thioredoxin domain, a classic component of cellular redox machinery, to a metallothionein domain, the hallmark of metal detoxification. The discovery broadens the known diversity of bacterial metallothioneins and hints at unexplored strategies bacteria use to survive in metal-contaminated environments.

The combination is more elegant than it might first appear. Thioredoxins are small, highly stable, and soluble proteins that participate in maintaining the redox balance of the cell, reducing disulfide bonds in target proteins through the activity of a conserved active-site motif. Metallothioneins, by contrast, are intrinsically disordered or loosely folded and owe their function to dense clusters of cysteine residues that coordinate metal ions. By fusing the two, evolution appears to have produced a protein in which the thioredoxin domain may confer improved stability and solubility on the metal-binding region, a property the authors highlight as particularly attractive for recombinant applications, where poorly soluble proteins are often difficult to produce and handle.

To test these ideas experimentally, the team took a recombinant approach. They expressed the hybrid protein heterologously in Escherichia coli, the workhorse of molecular biology, and dubbed the recombinant product TrxMt. The purified protein proved to be functionally bifunctional in exactly the way its architecture suggests. On one hand, it displayed disulfide-reducing activity, confirming that the thioredoxin domain remained catalytically competent in the chimera. On the other hand, it demonstrated heavy metal–binding capability, showing that the metallothionein domain could still capture metal ions despite being tethered to a folded enzymatic partner. Demonstrating both activities in a single polypeptide is the critical step, because a fusion that compromises either function would be little more than a biochemical curiosity.

The most consequential result came when the researchers asked whether the protein matters inside living cells, not just in a test tube. When TrxMt was overexpressed in E. coli, the engineered bacteria showed enhanced tolerance to multiple heavy metals compared with control cells. This in vivo effect demonstrates that the chimera is not merely capable of binding metals in principle but actively contributes to metal detoxification under physiological conditions. For a field in which characterized bacterial metallothioneins are scarce, the finding provides a concrete example of a bacterial hybrid protein whose expression measurably changes how cells withstand metal stress.

The implications extend well beyond bacterial physiology. Heavy metal contamination of soil and water is a persistent global problem, arising from mining, smelting, electroplating, battery manufacturing, and the improper disposal of industrial waste. Conventional remediation approaches, such as excavation, chemical precipitation, and ion exchange, can be expensive, energy-intensive, and disruptive to ecosystems. Bioremediation, which harnesses living organisms or their molecular components to capture or transform pollutants, offers a potentially gentler and more sustainable alternative. Metallothioneins have long been considered promising candidates for such applications precisely because of their high-affinity metal binding, and the authors suggest that TrxMt is a promising candidate for the bioremediation of heavy metal–contaminated environments.

What makes TrxMt especially interesting from a biotechnological standpoint is the pairing of detoxification with favorable biochemical properties. The thioredoxin domain’s contribution to stability and solubility could make the protein easier to produce at scale in recombinant systems, a persistent bottleneck for many environmentally useful proteins. A protein that is both robust and capable of sequestering toxic metals could, in principle, be deployed in engineered microbes designed to accumulate metals from contaminated sites, immobilized on biosorbent materials, or incorporated into biosensing platforms that detect metal pollution. The authors note that the protein combines metal detoxification with properties suitable for industrial and environmental applications, positioning it at the intersection of microbiology, structural biochemistry, and environmental engineering.

The study also carries lessons for how scientists explore protein diversity. Bacterial genomes harbor a vast reservoir of uncharacterized proteins, and domain-architecture searches of the kind that led to TrxA can reveal unexpected fusions that blend functions normally separated in eukaryotic biology. Because most known bacterial metallothioneins come from cyanobacteria, finding a thioredoxin–metallothionein chimera in Runella aurantiaca, a member of a different bacterial lineage, suggests that metal-binding proteins in bacteria may be more varied, and more structurally inventive, than the current literature reflects. Each new example refines our picture of how bacteria manage metal homeostasis and may point the way to additional proteins with useful binding properties.

There is, of course, a long road between a promising laboratory result and a field-deployable remediation technology. Future work will need to define the precise metal-binding capacity, selectivity, and kinetics of TrxMt, characterize its structure in detail, and evaluate its performance in realistic contaminated matrices where competing ions, variable pH, and organic matter complicate the chemistry. The Italian team, supported through national research programs including PNRR-funded projects, has nonetheless delivered a compelling proof of concept: a single bacterial protein that both keeps cellular redox machinery running and locks away toxic metals, and that measurably hardens cells against heavy metal assault. As contamination pressures mount worldwide, molecular chimeras like TrxMt may prove that sometimes the best environmental technologies are the ones evolution assembled first.

Subject of Research: A novel bacterial thioredoxin–metallothionein fusion protein with heavy metal-binding and disulfide-reducing activities

Article Title: Identification and characterization of TrxA: a novel bacterial thioredoxin–metallothionein chimera

Article References: Vitiello, A., Pirone, L., Filocaso, M., Fiorentino, G., Pedone, E., & Limauro, D. (2026). Identification and characterization of TrxA: a novel bacterial thioredoxin–metallothionein chimera. Applied Microbiology and Biotechnology, 110(1), Article 273. https://doi.org/10.1007/s00253-026-14002-w

Image Credits: AI Generated

DOI: 10.1007/s00253-026-14002-w

Keywords: metallothionein, thioredoxin, heavy metals, bioremediation, Runella aurantiaca, Escherichia coli, oxidative stress, metal homeostasis, recombinant protein, metal detoxification, Applied Microbiology and Biotechnology, Identification

The research team, working at Islamic Azad University’s Central Tehran Branch in collaboration with Shahid Beheshti University, set out to fill a conspicuous gap in the literature. Although Lactobacillus strains have long been associated with protective effects in the female genitourinary tract, their potential to safeguard male reproductive health under active bacterial challenge had never been rigorously tested in a controlled experimental model. The investigators designed a study using a native Iranian probiotic and postbiotic formulation containing three strains: Lactobacillus casei, Lactobacillus rhamnosus, and Lactobacillus helveticus. Their goal was to assess whether these interventions could protect renal integrity, testicular function, and sperm quality in rats experimentally infected with E. coli.

The experimental design was straightforward but comprehensive. Twenty-eight adult male Wistar rats, each weighing between 200 and 250 grams, were acclimatized for one week under controlled conditions of a 12-hour light-dark cycle and an ambient temperature of 23 degrees Celsius. The animals were then divided into four groups: an uninfected control group, a group infected orally with E. coli at a concentration of 10 to the eighth colony-forming units per millilitre for three consecutive days, and two infected groups that subsequently received either the probiotic mixture or the postbiotic preparation by daily oral gavage for 35 days. The postbiotic was prepared by culturing the probiotic powder, centrifuging the suspension, and filtering it through a 0.22-micrometre membrane to obtain cell-free metabolites, ensuring that no living bacteria remained in that treatment arm.

The results were striking. Histopathological examination of kidney tissue revealed that infected rats suffered severe damage, including vacuolar degeneration of tubular cells, extensive haemorrhage, collagen fibre deposition, cellular necrosis, and dense lymphocyte infiltration. Periodic acid–Schiff staining, which highlights basement membrane integrity, confirmed the extent of the injury. In contrast, rats treated with either probiotics or postbiotics showed markedly attenuated pathology, with reduced vacuolization, diminished inflammatory infiltration, and improved glomerular structure. Three blinded pathologists independently scored the sections, achieving an inter-observer agreement coefficient of 0.82, which lends considerable statistical weight to the visual findings.

The testes told a parallel story. Infection caused a significant drop in testicular weight and volume, shrank the diameter of seminiferous tubules from roughly 243 micrometres in controls to 173 micrometres in infected animals, and thinned the germinal epithelium that houses developing sperm cells. The lumen of the tubules, meanwhile, expanded abnormally, a hallmark of germ cell loss. Probiotic and postbiotic supplementation partially reversed these changes: tubule diameter recovered to around 212 to 214 micrometres, germ cell layer thickness rebounded from 149 to roughly 244 to 250 micrometres, and testicular weight climbed back toward control values. Sperm analysis reinforced the pattern, with infected rats showing reduced sperm counts, impaired viability, and abnormal morphology, all of which improved modestly with either treatment.

Blood chemistry provided further evidence of renal protection. Serum urea and creatinine, two classic markers of kidney dysfunction, rose sharply in infected rats compared with controls. Treatment with probiotics or postbiotics significantly lowered both markers relative to the infected group, with creatinine reductions reaching statistical significance at the p less than 0.01 level. Serum potassium followed a similar trend, while sodium concentrations remained unchanged across all groups, indicating that the interventions did not disturb electrolyte homeostasis. These biochemical improvements aligned closely with the histological recovery observed under the microscope.

At the molecular level, the researchers used real-time polymerase chain reaction to quantify the expression of genes governing apoptosis and inflammation. Infection drove a significant upregulation of Bax, a pro-apoptotic gene, alongside elevated expression of the inflammatory cytokines tumour necrosis factor-alpha and interleukin-6 in both kidney and testicular tissue. The anti-apoptotic gene Bcl-2, by contrast, was suppressed. Probiotic and postbiotic treatment flipped this profile: Bax, TNF-alpha, and IL-6 expression fell dramatically compared with infected animals, while Bcl-2 rose significantly. The authors interpret this dual modulation of apoptotic and inflammatory pathways as the central mechanism by which the interventions preserved tissue integrity.

Antioxidant capacity emerged as another critical piece of the puzzle. Total antioxidant capacity in both kidney and testicular tissue was significantly depleted by infection, reflecting the oxidative stress that bacterial pathogens impose on host cells. Supplementation restored these values substantially, with postbiotic-treated animals even showing a modest, though not statistically significant, increase above control levels in kidney tissue. This restorative effect on antioxidant defences likely complements the anti-inflammatory and anti-apoptotic actions, since reactive oxygen species and inflammatory signalling reinforce one another in a vicious cycle that probiotic metabolites appear able to interrupt.

The mechanisms behind these effects are consistent with a growing body of microbiome research. Lactobacillus strains produce lactic acid, hydrogen peroxide, and bacteriocins that directly inhibit pathogenic colonization, while reinforcing epithelial barrier function and modulating toll-like receptor signalling, dendritic cell activity, and cytokine production. Postbiotics, comprising proteins, lipids, short-chain fatty acids, and other fermentation products, deliver many of these benefits without the logistical and safety concerns associated with live microorganisms, which is particularly relevant for immunocompromised patients. The multi-strain approach used here may also amplify protection, as prior studies suggest that combining strains with diverse metabolic and immunomodulatory properties produces synergistic effects.

The authors are careful to note that recovery was partial rather than complete, and that the study was conducted in a rodent model with a defined bacterial challenge rather than the complex, recurrent infections seen in clinical practice. Dose optimization, strain selection, timing of administration, and long-term safety evaluation all remain open questions before such interventions can be recommended for human use. Nevertheless, the findings add meaningful weight to the argument that microbiota-based therapies could serve as adjuncts or alternatives to antibiotics at a moment when antimicrobial resistance is escalating globally. If the protective effects observed in these rats translate to humans, a simple mixture of Lactobacillus strains or their metabolites might one day help men preserve both kidney function and fertility in the face of one of medicine’s most persistent bacterial adversaries.

Subject of Research: Protective effects of Lactobacillus-derived probiotics and postbiotics on renal and reproductive function in E. coli-infected rats

Article Title: Protective Effects of Lactobacillus‐Derived Probiotics and Postbiotics on Renal and Reproductive Function in Escherichia coli–Infected Rats

Article References: Sedghi, S., Keshtmand, Z., & Hosseini, S. (2026). Protective Effects of Lactobacillus ‐Derived Probiotics and Postbiotics on Renal and Reproductive Function in Escherichia coli –Infected Rats. Veterinary Medicine and Science, 12(6), Article e71258. https://doi.org/10.1002/vms3.71258

Image Credits: AI Generated

DOI: 10.1002/vms3.71258

Keywords: probiotics, postbiotics, Lactobacillus, Escherichia coli, urinary tract infection, male infertility, kidney injury, testicular function, sperm quality, oxidative stress, apoptosis, antimicrobial resistance

The urgency behind the search is difficult to overstate. According to recent estimates from the World Health Organization, bacterial antimicrobial resistance was associated with approximately 1.14 million deaths in 2021 alone. Between 1990 and 2021, deaths linked to antimicrobial resistance among adults aged 70 and older rose by more than 80 percent, and projections suggest that by 2050 resistance could be directly responsible for roughly 1.91 million deaths annually, with a further 8.22 million deaths associated with resistant infections. Gram-negative bacteria such as E. coli, Acinetobacter baumannii, Pseudomonas aeruginosa and Shigella are among the worst offenders, wielding structurally dynamic cell envelopes, antibiotic-inactivating enzymes, remodeled porins, efflux pumps and altered drug targets that render many existing drugs ineffective.

What makes the new study particularly compelling is its focus on biofilms, the dominant form of microbial growth in nature. Biofilms are structured communities of bacteria encased in a self-produced extracellular matrix of polysaccharides, proteins, nucleic acids and lipids. This matrix shields the inhabitants from antibiotics and immune attack, restricts drug penetration, and supports cell-to-cell communication, making biofilm-associated infections notoriously difficult to eradicate. Both E. coli and Shigella form robust biofilms that dramatically amplify their resistance. Most previous screens of natural products have tested only free-floating, planktonic bacteria, leaving antibiofilm activity largely unexplored. The Indian research team set out to close that gap by examining not just whether their fungal extract killed bacteria, but whether it could prevent biofilms from forming and dismantle those already established.

The journey began with leaves collected from healthy A. officinalis trees. After thorough washing and surface sterilization with ethanol and sodium hypochlorite, leaf segments were placed on potato dextrose agar supplemented with antibiotics to suppress bacterial contaminants. Fungal hyphae emerged only from the cut edges of the sterilized segments, confirming that the fungus truly lived inside the plant tissue rather than on its surface. Morphological examination under light and field-emission scanning electron microscopes revealed dense, septate, branched hyphae and a gray to grayish-green, velvety colony. Molecular identification followed: the researchers amplified the internal transcribed spacer region of the fungal genome with the universal primers ITS1 and ITS4, sequenced the product, and compared it against the Unite 9.0 database. The result was a 100 percent match with Daldinia sp., confirmed by a maximum-likelihood phylogenetic analysis built from the closest neighbors in the NCBI database.

To coax the fungus into releasing its chemical defenses, the team grew it in potato dextrose broth for 21 days in the dark, then extracted the culture filtrate with ethyl acetate and methanol. The ethyl acetate fraction, designated AO-EA, proved the more potent of the two and became the focus of all subsequent experiments. In agar well diffusion assays, the crude extract produced clear zones of inhibition ranging from 13.67 to 17.33 millimeters against E. coli and Shigella. Those zones are smaller than the 30 to 33 millimeters produced by the fluoroquinolone antibiotic ciprofloxacin, but the comparison is not straightforward. Ciprofloxacin is a purified single compound with a well-characterized target, whereas AO-EA is a crude mixture in which any individual active molecule is present at relatively low concentration, diluted among inactive constituents. Purification and enrichment of the active principles could substantially improve potency.

Quantitative testing reinforced the promise. Broth microdilution following Clinical and Laboratory Standards Institute guidelines yielded minimum inhibitory concentrations of 625 micrograms per milliliter for E. coli and 312.5 micrograms per milliliter for Shigella, with minimum bactericidal concentrations of 625 micrograms per milliliter for both organisms, indicating that the extract does not merely stall growth but kills the cells outright. Time-kill kinetics over 24 hours showed a significant, progressive decline in viable counts of both pathogens at the MIC, while untreated controls grew normally. Field-emission scanning electron microscopy then revealed what the killing looked like at the cellular level: after three hours of exposure, treated cells appeared deformed, wrinkled and broken, with altered shape and size, in stark contrast to the smooth, intact rods of the untreated controls.

The mechanism of action came into sharper focus through two complementary techniques. Flow cytometry with propidium iodide, a red fluorescent dye that enters only cells with compromised membranes, showed that after three hours at twice the MIC, 84.04 percent of E. coli cells and 62.15 percent of Shigella cells had lost membrane integrity, a rightward shift in fluorescence that signals catastrophic permeability failure. Confocal laser scanning microscopy confirmed the same pattern visually, with treated cells glowing red in the propidium iodide channel. The confocal experiments also used the dye DCFDA to probe for reactive oxygen species, and the results were striking: treated cells displayed a surge in fluorescence comparable to that produced by hydrogen peroxide, indicating that the extract floods the bacteria with oxidative stress. Membrane disruption and ROS-mediated damage together appear to form a two-pronged killing strategy.

The antibiofilm results may be the study’s most impressive contribution. In crystal violet staining assays, AO-EA at its MIC prevented new biofilm formation by 93.03 percent for E. coli and 89.38 percent for Shigella. More remarkably, when the researchers allowed mature 24-hour biofilms to establish first and then added the extract, biomass fell by 86.20 percent for E. coli and 83.02 percent for Shigella. Published criteria consider inhibition above 50 percent to be good antibiofilm activity, and the extract not only cleared that bar decisively but approached the performance of ciprofloxacin, which achieved just over 90 percent inhibition. An MTT assay, which measures the metabolic activity of living cells through a colorimetric reaction, showed that only around 10 to 15 percent of biofilm cells remained viable and metabolically active after treatment. Scanning electron micrographs of treated biofilms revealed scattered, loosely associated cells instead of the dense, layered architecture of untreated communities, pointing to impaired adhesion and destabilized cell-to-surface interactions.

Finally, high-resolution liquid chromatography mass spectrometry on an Orbitrap platform identified 15 distinct metabolites in the extract, spanning antimicrobial peptides, carboxylic acids, alkaloids, polyketides and phenols. Among the notable constituents were citrinin, a polyketide recently reported to show antimicrobial activity from other mangrove-derived fungi; radicinin, known to inhibit the grapevine pathogen Xylella fastidiosa; homovanillic acid, azelaic acid, xanthine, 5-hydroxyindole-3-acetic acid, gluconic acid and anthranilic acid, all of which have documented antibacterial credentials in other fungal systems; and peptide compounds including glycyl-L-leucine and two cyclic dipeptides of the octahydropyrrolo[1,2-a]pyrazine-dione family. Several of these molecules had not previously been reported from the genus Daldinia, although related phenols and carboxylic acids from Daldinia eschscholtzii have shown antibacterial and antibiofilm effects elsewhere. The extreme conditions of mangrove ecosystems, with their fluctuating salinity, tides and oxygen levels, are thought to drive these fungi toward chemically novel metabolism, and the competition among microorganisms packed into plant tissues likely selects for broad-spectrum defensive chemistry.

The authors caution that much work remains before any clinical application. The active compounds must be isolated and purified, their individual contributions disentangled, their mechanisms confirmed at the molecular level, and their safety and efficacy tested far beyond the culture dish. Nevertheless, the study demonstrates that a single fungus plucked from the leaves of an ecologically important, traditionally medicinal mangrove can simultaneously kill planktonic Gram-negative pathogens, shatter their membranes, provoke lethal oxidative stress, block nearly all new biofilm formation and dismantle the majority of established biofilms. As resistance continues to erode the value of existing antibiotics, such findings suggest that the world’s mangrove forests, among the most productive and least explored ecosystems on Earth, may hold a substantial share of the next generation of anti-infective drugs, provided they are studied before they disappear.

Subject of Research: Antimicrobial and antibiofilm activity of secondary metabolites from the mangrove endophytic fungus Daldinia sp. isolated from Avicennia officinalis

Article Title: Antimicrobial and Antibiofilm Activity of an Endophytic Fungus, Daldinia sp. Isolated From Avicennia officinalis

Article References: Dutta, N., Kumari, N., Lather, A., & Kumar, K. (2026). Antimicrobial and Antibiofilm Activity of an Endophytic Fungus, Daldinia sp. Isolated From Avicennia officinalis. MicrobiologyOpen, 15(5), Article e70422. https://doi.org/10.1002/mbo3.70422

Image Credits: AI Generated

DOI: 10.1002/mbo3.70422

Keywords: endophytic fungus, Daldinia, mangrove, Avicennia officinalis, antimicrobial resistance, antibiofilm, Escherichia coli, Shigella, secondary metabolites, LC-HRMS, membrane disruption, reactive oxygen species

The chemistry behind the study rests on the Claisen-Schmidt condensation, a base-catalyzed reaction that joins an aromatic aldehyde with a ketone-bearing precursor to form conjugated enone linkages. Using this approach, the researchers assembled derivatives labeled 2 through 5, each carrying the benzenesulfonamide scaffold decorated with different heterocyclic appendages, including pyrazole rings fused or hybridized with pyrrolidine and thiophene units. The sulfonamide group itself has a storied history in medicine, having anchored the first generation of synthetic antibiotics in the 1930s, and it remains a versatile pharmacophore because its polar chemistry allows it to form hydrogen bonds with biological targets. By varying the heterocyclic partners attached to this core, the team could probe how subtle structural changes alter biological activity, a strategy known as structure-activity relationship exploration.

The larvicidal half of the study targeted Wohlfahrtia magnifica, the spotted flesh fly, whose larvae are obligate parasites that invade the living tissue of warm-blooded animals and cause a devastating condition known as traumatic myiasis. The disease inflicts severe losses in livestock and occasionally affects humans, and control options are narrowing as conventional insecticides lose efficacy and face regulatory restrictions. When the researchers exposed W. magnifica larvae to the compounds at a concentration of 25 milligrams per gram, the thienyl-pyrazole-hybridized derivative 5 emerged as the clear winner, driving cumulative mortality to approximately 92 percent by the fourth day of treatment. The other derivatives showed weaker effects, underscoring how the thiophene-pyrazole combination appears to be the key structural feature for insecticidal potency in this series.

What makes the study particularly compelling is the microscopic evidence of how the winning compound kills. Histopathological examination of treated larvae revealed extensive breakdown of the cuticle, the tough outer armor that insects depend on for protection and water balance. Beneath the surface, the muscle architecture collapsed, with myofibrils, the contractile fibers of larval muscle, fragmenting into disorganized debris. The mitochondria, the organelles that power cellular metabolism, swelled severely, a hallmark of energy failure and irreversible cellular stress. Perhaps most striking was the fate of the collagen-like extracellular matrix that supports larval tissues: quantitative assessment showed its abundance plummeting from roughly 80 percent in untreated specimens to below 15 percent after treatment, indicating a progressive disintegration of the structural scaffolding that holds the insect’s body together.

To determine whether the dying cells were undergoing programmed cell death, the team turned to acridine orange, a fluorescent dye that binds nucleic acids and reveals nuclear morphology under ultraviolet light. Staining of treated larvae showed condensation and fragmentation of nuclei in a treatment-dependent pattern, the classic cytological signature of apoptosis. This finding suggests that compound 5 does not simply poison larvae indiscriminately but triggers an organized self-destruction program within their cells, a mechanism that could be exploited to design more targeted and environmentally selective pest control agents in the future.

The antibacterial arm of the study focused on a different threat: multidrug-resistant Gram-negative pathogens. Here the ranking flipped. The pyrrolidine-pyrazole hybrid, compound 2, displayed selective and dose-dependent inhibition of Klebsiella pneumoniae, producing inhibition zones between 15 and 28 millimeters with a minimum inhibitory concentration of 10 milligrams per milliliter, and also curbed Escherichia coli with zones of 9 to 16 millimeters and an MIC of 25 milligrams per milliliter. Notably, the compound showed no activity against Staphylococcus aureus, a Gram-positive species, meaning its spectrum is confined to the outer-membrane-bearing bacteria that are hardest to attack with existing drugs. Klebsiella pneumoniae in particular has become one of the world’s most alarming reservoirs of resistance genes, capable of transferring drug tolerance to other species, so any new chemical scaffold with activity against it attracts immediate attention.

Scanning electron microscopy provided visual confirmation of the antibacterial mechanism at the cellular level. Treated bacterial cells exhibited rupture of the cell envelope and wholesale structural collapse, images consistent with a compound that damages the membrane and wall architecture rather than merely slowing growth. To pin down the molecular target, the researchers ran in vitro enzyme assays against two essential bacterial enzymes: DNA gyrase B and topoisomerase IV. These enzymes belong to the type II topoisomerase family and are responsible for managing the topological stress of DNA replication and transcription; they are the targets of fluoroquinolone antibiotics, against which resistance has spread widely. Compound 2 inhibited E. coli DNA gyrase B with an IC50 of 3.188 micromolar and topoisomerase IV with an IC50 of 14.288 micromolar, demonstrating genuine enzymatic inhibition rather than nonspecific toxicity.

Computational modeling then connected the biochemical data to atomic-scale structure. Molecular docking simulations placed compound 2 firmly within the ATP-binding cavities of both enzymes, yielding docking scores of minus 10.88 kilocalories per mole for DNA gyrase B and minus 9.98 kilocalories per mole for topoisomerase IV. Scores in this range indicate energetically favorable binding poses, and the fact that the compound engages both members of the topoisomerase family is significant because dual targeting makes it harder for bacteria to develop resistance through a single mutation. The docking results align with the enzyme assays, giving the inhibition data a plausible structural explanation and providing a template for future medicinal chemistry optimization.

Before any compound can move toward drug development, it must pass a gauntlet of predicted properties collectively known as ADMET profiling, covering absorption, distribution, metabolism, excretion, and toxicity. In silico analysis of the derivatives indicated good oral bioavailability, with a predicted human intestinal absorption rate of 94.87 percent for the lead compound, alongside a favorable drug-likeness profile and an acceptable safety window with respect to the hERG potassium channel, a common early warning screen for cardiac toxicity risk. These computational predictions do not replace laboratory pharmacokinetic testing, but they suggest that the scaffold is worth advancing rather than fundamentally flawed in its drug-like character.

The study’s dual findings, a potent larvicidal compound and a multi-target antibacterial lead emerging from the same synthetic series, illustrate the value of systematic heterocycle design around a proven pharmacophore. Compound 5 now stands as a candidate for further development against myiasis-causing flies, while compound 2 offers a starting point for optimizing inhibitors of bacterial DNA gyrase and topoisomerase IV at a time when Gram-negative resistance continues to erode the clinical utility of older antibiotic classes. The authors, led by Ahmed Abdou O. Abeed of Assiut University and Mustafa A. Fawzy of Taif University, acknowledge funding from Taif University’s Deanship of Graduate Studies and Scientific Research. As with all early-stage discovery work, the path from laboratory potency to practical insecticide or antibiotic is long, requiring toxicity studies in animal models, formulation development, and resistance selection experiments, but the combination of histological, ultrastructural, biochemical, and computational evidence assembled here gives both lead compounds a well-documented foundation for the next phase of evaluation.

Subject of Research: Synthesis and dual larvicidal and antibacterial evaluation of novel benzenesulfonamide derivatives

Article Title: Novel benzenesulfonamide derivatives as larvicidal and antibacterial agents: insights from histopathological studies, molecular docking, and ADMET profiling

Article References: Abeed, A. A. O., Fawzy, M. A., Abd El-Aziz, F. E.-Z. A., Alsharif, H., Afifi, T. H., Shikhoun, M. E. H., Ahmed, H. A., Nossier, E. S., & Kishk, F. N. M. (2026). Novel benzenesulfonamide derivatives as larvicidal and antibacterial agents: insights from histopathological studies, molecular docking, and ADMET profiling. 3 Biotech, 16(10), Article 450. https://doi.org/10.1007/s13205-026-05060-y

Image Credits: AI Generated

DOI: 10.1007/s13205-026-05060-y

Keywords: benzenesulfonamide, larvicidal agents, Wohlfahrtia magnifica, antibacterial activity, DNA gyrase B, topoisomerase IV, Klebsiella pneumoniae, Escherichia coli, molecular docking, ADMET profiling, histopathology, antimicrobial resistance

The problem arises because the most widely used rapid sample preparation method, the commercially available MBT Sepsityper kit, was designed for a task that does not require living bacteria. The kit uses a proprietary lysis buffer, thought to contain ionic detergents such as sodium dodecyl sulphate, to rupture red blood cells, followed by high-speed centrifugation at around 16,000 times gravity to pellet the bacteria and discard cellular debris. The resulting organisms are fed into matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, which identifies pathogens from their protein and lipid fingerprints. For that purpose, viability is irrelevant. But the new generation of rapid phenotypic antimicrobial susceptibility tests, which promise results within two to three hours, depends entirely on bacteria that are actively dividing the moment they emerge from the extraction process.

This distinction matters most for Gram-positive pathogens. Organisms such as Staphylococcus aureus, which together with other Gram-positive bacteria account for more than half of bloodstream infections, possess a thick cell wall and membrane architecture that renders them far more vulnerable to detergent damage than their Gram-negative counterparts such as Escherichia coli. Previous studies have already hinted at the problem, reporting lower identification scores for Gram-positive organisms processed with Sepsityper. The Southampton group, led by Hywel Morgan and Daniel Spencer, set out to quantify exactly how much harm five different blood lysis protocols inflict on bacterial viability during the earliest stages of growth, the window that rapid susceptibility assays cannot afford to lose.

The researchers spiked healthy human blood with laboratory strains of E. coli and S. aureus, incubated the mixtures in standard aerobic blood culture bottles until they flagged positive, and then processed each bottle with one of five extraction chemistries: the Sepsityper kit, saponin alone, an ammonium chloride and potassium bicarbonate buffer, deionised water lysis by hypoosmotic shock, and a combination of saponin with the non-ionic detergent Triton X-100 supplemented with reducing agents to suppress reactive oxygen species. Each protocol lyses red blood cells by a different mechanism, from detergent-mediated membrane permeabilisation to osmotic swelling, and each carries its own trade-off between how completely the blood cells are destroyed and how gently the bacteria are treated.

To judge the outcome, the team turned to microfluidic impedance cytometry, a label-free technique that measures the electrical properties of thousands of individual cells as they stream through a microchannel lined with microelectrodes. An alternating voltage is applied at two frequencies, 5 MHz and 40 MHz. At the lower frequency the signal reflects cell volume, while at the higher frequency it is sensitive to the cell membrane and wall. Because the channel is only about 20 by 40 micrometres, bacteria can be counted and characterised one by one, even in the presence of residual red cell ghosts and debris, provided their electrical signatures do not overlap. The technique has already been shown to detect antibiotic-induced changes in bacterial impedance within two hours, forming the basis of a rapid susceptibility method known as iFAST.

The impedance data revealed striking differences between the extraction protocols. For E. coli, which reaches very high concentrations in blood culture bottles, all five methods yielded counts in agreement with conventional colony counting, and the bacteria resumed normal growth after only a brief 30-minute lag. For S. aureus, which grows more slowly and is present at roughly tenfold lower concentrations at the time the bottle flags positive, the picture changed dramatically. Samples treated with Sepsityper produced far fewer detectable organisms immediately after extraction, and the population did not begin to grow until two and a half hours had passed. Untreated and saponin-treated samples, by contrast, showed only a one-hour delay before entering exponential growth, with doubling times of around 65 to 67 minutes that were statistically indistinguishable from each other.

Independent confirmation came from optical flow cytometry using live/dead fluorescent staining. The team labelled bacteria with SYTO 9, a green dye that enters all cells, and propidium iodide, a red dye that penetrates only cells with damaged membranes. Immediately after Sepsityper extraction, most S. aureus cells showed strong propidium iodide signal, indicating compromised membranes, while saponin-treated cells looked essentially identical to untreated controls and recovered as quickly. The likely culprit is the ionic detergent in the Sepsityper buffer, which can permeabilise bacterial membranes and may also provoke oxidative stress. Colony imaging after overnight incubation reinforced the finding: S. aureus colonies isolated with Sepsityper were significantly smaller than those from untreated samples, whereas saponin-treated colonies showed no significant difference.

Extraction efficiency told a similar story. Measured against colony counts from untreated cultures, viable E. coli recovery ranged from 37 to 54 percent across the protocols, while S. aureus recovery ranged from just 5 to 35 percent. Saponin delivered the highest impedance-based efficiency for S. aureus at 35 percent and produced the cleanest samples, with debris particles small enough to be separated from the bacteria electrically. The ammonium chloride protocol generated so much debris overlapping with the S. aureus population that accurate counting became impossible, and deionised water lysis performed worst of all, possibly because S. aureus cells adhered to red blood cells and sedimented away with them during centrifugation. For E. coli, the data even suggested that lysis and centrifugation may be unnecessary, since fast-growing Gram-negative organisms can be discriminated from blood cells directly.

Beyond viability, the study highlights a subtler advantage of impedance cytometry for the diagnostic workflow itself. Preparing the inoculum for a phenotypic susceptibility test normally relies on turbidity matching against a McFarland standard, but blood cells and debris inflate turbidity and skew the measurement. Because impedance cytometry counts each bacterium as a discrete electrical event and can distinguish bacteria from red cells, ghosts and platelets by their size and high-frequency phase, it offers a direct route to accurate inoculum preparation at the concentration recommended by EUCAST guidelines. The technique can even discriminate E. coli from S. aureus by their electrical phase, an analogue of conventional Gram staining performed without any reagents or stains.

The implications reach well beyond the laboratory bench. Any rapid susceptibility platform that promises answers within three hours of a blood bottle flagging positive will be defeated if its sample preparation quietly kills or stuns a large fraction of the pathogens, and the organisms most likely to be harmed are precisely the Gram-positive bacteria that dominate bloodstream infections. The Southampton results point to saponin, a mild natural detergent, as the chemistry of choice for preserving viable organisms, and the team now plans to integrate on-chip lysis, automated washing and size-based separation into a streamlined microfluidic sample preparation system. Clinical samples, polymicrobial cultures and a broader panel of Gram-positive pathogens remain the next hurdles, but the study makes clear that the road to same-hour antibiotic decisions runs through gentler chemistry.

Subject of Research: Rapid isolation of viable bacteria from positive blood cultures using microfluidic impedance cytometry to compare blood lysis protocols for antimicrobial susceptibility testing

Article Title: Isolating viable bacteria from positive blood cultures: impedance cytometry analysis

Article References: Isolating viable bacteria from positive blood cultures: impedance cytometry analysis. (n.d.). https://doi.org/10.1007/s10544-026-00847-5

Image Credits: AI Generated

DOI: 10.1007/s10544-026-00847-5

Keywords: bloodstream infections, sepsis, antimicrobial susceptibility testing, impedance cytometry, microfluidics, Sepsityper, saponin, Staphylococcus aureus, Escherichia coli, bacterial viability, MALDI-TOF, antimicrobial resistance

The research team set out to answer a deceptively simple question: how does temperature affect the abundance and composition of antibiotic resistance genes in activated sludge systems, when everything else is held constant? This question matters because real-world treatment plants experience seasonal swings, and previous field studies have struggled to disentangle the effects of temperature from the effects of changing influent composition. Winter brings not only colder basins but also different patterns of water use, different chemical loads, and different microbial communities arriving at the plant. To isolate temperature as a single variable, the researchers designed an elegant controlled experiment conducted directly at an urban wastewater treatment plant in Portugal, ensuring that the wastewater feeding their experimental systems reflected genuine, real-world conditions rather than synthetic laboratory mixtures.

Two laboratory-scale conventional activated sludge systems were operated side by side for 147 days under identical conditions, with one crucial exception. The control system was maintained at approximately 20 degrees Celsius, a temperature representative of moderate operating conditions, while the test system was run sequentially at 10, 5, 15, and 28 degrees Celsius. This sequential design allowed the researchers to observe how the same microbial community responded as the thermal regime shifted up and down over time. Throughout the experiment, the team sampled the feed, which consisted of primary effluent from the host treatment plant, as well as the treated effluent and the sludge from each system. These samples were analyzed for physicochemical parameters, fecal indicator bacteria, the abundance of specific antibiotic resistance genes, and the composition of the bacterial communities using molecular profiling techniques.

The results revealed a striking interplay between what enters the plant and what happens inside it. The patterns of antibiotic resistance genes in the treated effluent were clearly influenced by the composition of the incoming feed, confirming that influent characteristics drive much of the resistance dynamics in activated sludge systems. However, temperature exerted an additional, independent influence on top of this influent-driven variability. The most dramatic effect emerged when the test system was operated at 5 degrees Celsius. Under this cold regime, the abundance of intI1, a gene widely used as a proxy for anthropogenic antibiotic resistance pollution and a marker of mobile genetic elements, dropped significantly compared with the control system held at 20 degrees Celsius.

Even more importantly from a clinical standpoint, the cold treatment significantly reduced genes of direct medical relevance, including blaIMP, which confers resistance to carbapenem antibiotics, a last-resort class of drugs used against multidrug-resistant infections, and qnrS, which is associated with reduced susceptibility to fluoroquinolones. These are not obscure genetic markers; carbapenem resistance in particular represents one of the most alarming developments in infectious disease medicine. The observation that a simple operational parameter like temperature could measurably suppress these genes in treated effluent carries substantial implications for how treatment plants might be managed to limit the environmental dissemination of resistance.

To understand why cold temperatures had this effect, the researchers turned to the bacterial community composition data. The shifts in gene abundance were associated with changes in the microbial community itself, particularly a decrease in genera such as Acinetobacter and Escherichia-Shigella, both of which are considered potential hosts for antibiotic resistance genes and both of which include clinically significant pathogens. In other words, the cold did not simply disable the genes while leaving their carriers intact; it appears to have reduced the fitness of the key bacterial hosts that harbor and propagate these genes. When the host organisms decline, the genes they carry decline with them, offering a mechanistic explanation for the observed reductions in effluent ARG loads.

An equally important finding concerned where in the system these effects occurred. The researchers found no significant differences in antibiotic resistance gene abundance in the sludge fraction between the cold and control systems, indicating that temperature mainly influenced ARG persistence in the liquid phase. This distinction matters because the liquid effluent is what gets discharged into receiving rivers and coastal waters, while sludge is typically handled separately, often through anaerobic digestion and land application. The selective reduction of ARGs in the liquid phase suggests that low-temperature operation specifically curtails the release of resistance genes into the aquatic environment, which is one of the principal pathways by which resistance spreads from human settlements into natural ecosystems.

The temperature effect extended beyond resistance genes to the removal of fecal indicator organisms. Reductions of Escherichia coli, the standard marker of fecal contamination, were significantly greater at 5 degrees Celsius than at the control temperature, indicating that cold operation also enhanced the removal of this pathogen indicator from the effluent. This finding adds to the appeal of cold operation from a water quality perspective, although the researchers caution that the picture is not uniformly positive. Low temperature impaired nutrient removal, a critical function of activated sludge systems that protects receiving waters from eutrophication. Nitrifying bacteria and other nutrient-cycling microorganisms are notoriously sensitive to cold, and their slowed activity under low-temperature conditions translated into poorer nutrient removal performance.

Crucially, however, the overall effluent quality remained within discharge limits even during the cold-temperature runs, meaning that the trade-off between enhanced ARG suppression and reduced nutrient removal did not push the system out of regulatory compliance in this study. This balance is central to any practical consideration of the findings. Treatment plant operators cannot simply chill their reactors without consequence, but the study demonstrates that the penalty may be more manageable than feared, while the benefit, a significant reduction in clinically relevant resistance genes entering the environment, could be substantial. The authors frame temperature as an important operational driver of antibiotic resistance dissemination, a variable that deserves deliberate attention rather than passive acceptance.

The broader significance of this work lies in its contribution to the growing field of evidence-based wastewater management for antibiotic resistance control. As concerns mount over the role of treatment plants as conduits for resistance genes into rivers, irrigation systems, and drinking water sources, engineers and regulators are searching for interventions that are feasible within existing infrastructure. This study suggests that temperature, a parameter already monitored and in some contexts already manipulated, could be part of that toolkit, particularly in climates or seasons where colder operation is achievable. It also underscores a fundamental ecological principle: the fate of antibiotic resistance genes in engineered environments is governed not only by the genes themselves but by the fitness of the microbial communities that carry them. By shifting the thermal environment, operators can shift the competitive balance of those communities, and with it, the resistance burden flowing out of the plant and into the world downstream.

Subject of Research: Effect of temperature on antibiotic resistance gene dynamics in conventional activated sludge wastewater treatment

Article Title: Influent-driven antibiotic resistance dynamics are constrained by low temperatures in conventional activated sludge systems

Article References: Influent-driven antibiotic resistance dynamics are constrained by low temperatures in conventional activated sludge systems. (n.d.). https://doi.org/10.1007/s00253-026-14036-0

Image Credits: AI Generated

DOI: 10.1007/s00253-026-14036-0

Keywords: antibiotic resistance genes, wastewater treatment, activated sludge, temperature, intI1, blaIMP, qnrS, Escherichia coli, Acinetobacter, bacterial community, nutrient removal, environmental microbiology

Fulvic acid belongs to a family of organic materials known as humic substances, the dark, chemically complex residues left behind when microorganisms decompose plant and animal matter. Humic substances are conventionally divided into three fractions according to their solubility: humic acid, which dissolves in alkaline solutions but precipitates when the pH drops below 2; humin, which is insoluble under all conditions; and fulvic acid, the fraction that remains soluble across the entire pH range. This solubility gives fulvic acid unusual versatility, and its molecular architecture is studded with reactive functional groups, including carboxyl, phenolic, quinone, carbonyl, hydroxyl, and amine moieties, many of which have documented biological activity. The exact structure of fulvic acid remains incompletely understood, but capillary electrophoresis and mass spectrometry studies suggest it should be viewed not as a single high-molecular-weight compound but as an assembly of smaller molecules that associate in solution.

The research team collected cow dung from cattle farms in village Chanesar Chachar, Taluka Pano Aqil, District Sukkur, dried it for five to six days at room temperature, and ground it into a fine powder. Extraction followed the protocol of the International Humic Substances Society: the powdered manure was mixed with 80 milliliters of 5 percent sodium hydroxide solution, shaken for four hours, and left to stand for twelve hours. After dilution with deionized water and centrifugation at 3000 revolutions per minute, hydrochloric acid was added to bring the pH down to between 1 and 2, precipitating the humic acid fraction and leaving fulvic acid in the supernatant, which was then collected and dried for analysis. The method is deliberately simple, relying on cheap reagents and standard laboratory equipment, which is precisely what makes the approach attractive for resource-limited settings.

One of the study’s most technically interesting observations concerns extraction efficiency. When 25 grams of dung powder were processed per liter of 0.5 N sodium hydroxide, the yield was 2.5 grams, or 10 percent of the starting mass. Doubling the raw material to 50 grams produced 4 grams, an 8 percent yield, and 100 grams yielded just 6 grams, or 6 percent. The percentage yield therefore falls as the solid loading rises, an inverse relationship the authors attribute to reduced solvent accessibility and less efficient mass transfer at higher concentrations, possibly compounded by saturation effects in the alkaline solubilization process. For anyone hoping to scale up production, the lesson is counterintuitive but clear: less material per batch extracts more efficiently, a trade-off between throughput and yield that will need optimization before any industrial process could be contemplated.

Characterization of the extracted material relied on three complementary analytical techniques. Ultraviolet-visible spectroscopy showed a maximum absorption at 316 nanometers, closely matching a commercial fulvic acid standard from Aldrich, indicating similar chromophoric structures arising from pi-to-pi-star transitions in aromatic and conjugated systems. Fourier transform infrared spectroscopy then mapped the functional group chemistry: a broad band between 3400 and 2900 reciprocal centimeters corresponding to O-H and N-H stretching, a sharp peak near 2929 from aliphatic C-H stretching of methyl and methylene groups, bands between 1598 and 1507 assigned to aromatic carbon-carbon stretching and quinone and conjugated carbonyl contributions, a peak at 1420 reflecting carboxylate asymmetric stretching and phenolic C-O stretching, and a strong absorption at 1034 from C-O stretching of alcohols and polysaccharide structures. The spectrum of the extracted material closely paralleled that of the standard, confirming successful isolation of humic-type functional groups.

X-ray diffraction completed the structural picture. The diffraction pattern displayed a broad background hump between 15 and 35 degrees two-theta, the signature of a largely amorphous material, superimposed with several sharp crystalline peaks. The most intense peak appeared at approximately 44.71 degrees with a d-spacing of 2.0276 angstroms, and a second prominent peak at 31.74 degrees with a d-spacing of 2.8195 angstroms. The combination of diffuse scattering and discrete reflections indicates a semi-crystalline structure in which small crystalline domains are embedded in a dominant amorphous matrix, with minimal impurities, consistent with the successful isolation of a heterogeneous natural organic mixture rather than a single crystalline compound.

The antimicrobial testing followed classical microbiological methodology. Reference strains of E. coli (ATCC 25922), P. aeruginosa (ATCC 27853), and Salmonella Typhi (ATCC 14028) were cultured on Mueller-Hinton agar, and inocula were standardized to the 0.5 McFarland turbidity standard. Fulvic acid was dissolved in dimethyl sulfoxide, with the solvent held at or below 1 percent by volume and a solvent-only control included to rule out false positives. In the agar well diffusion assay, the dose-response relationship was unambiguous. At 0.1 grams per 5 milliliters, no inhibition zones appeared against any of the three organisms. At 0.2 grams per 5 milliliters, zones of 11, 10, and 9 millimeters emerged for E. coli, P. aeruginosa, and S. Typhi respectively. Raising the concentration to 0.4 grams per 5 milliliters expanded the zones to 12, 11, and 11 millimeters, and at 0.8 grams per 5 milliliters the zones reached 14, 15, and 12 millimeters. The maximum concentration tested, 1.6 grams per 5 milliliters, produced the largest zones: 16 millimeters against E. coli, 15 against P. aeruginosa, and 14 against S. Typhi.

Quantitative susceptibility testing sharpened the hierarchy. Using a two-fold dilution series from 1000 down to 31.25 micrograms per milliliter, the team determined minimum inhibitory concentrations ranging from 250 to 1000 micrograms per milliliter and minimum bactericidal concentrations from 500 to 2000 micrograms per milliliter. E. coli proved the most susceptible, inhibited at 250 micrograms per milliliter, followed by P. aeruginosa at 500, while Salmonella Typhi required a full 1000 micrograms per milliliter. The authors connect this graded susceptibility to differences in cell envelope architecture: P. aeruginosa deploys a famously impermeable outer membrane and active efflux pumps, while E. coli and S. Typhi present different membrane compositions and permeability characteristics. Mechanistically, the antimicrobial action is attributed to fulvic acid’s phenolic, carboxylic, and quinone functional groups, which may disrupt microbial membranes, chelate essential metal ions, and generate redox-mediated oxidative stress, mechanisms well documented for structurally related phytophenolic compounds.

The authors are careful to frame these results as preliminary, and the caveats deserve emphasis. The activity was demonstrated only against planktonic, free-floating bacteria in vitro, using agar diffusion and broth dilution assays. No mechanistic studies of bacterial interaction pathways, no cytotoxicity profiling on mammalian cell lines, no stability or bioavailability assessments, and no tests against clinically resistant strains or biofilm models were performed. The dataset, as the researchers themselves state, is insufficient to support direct application in biomedical, agricultural, or environmental systems, and any translational implications must be considered tentative. What the study does establish is a proof of concept: cow dung is a viable, low-cost raw material for fulvic acid extraction, the isolated product carries the structural fingerprints of authentic fulvic acid, and it exerts measurable, concentration-dependent antibacterial activity against three major Gram-negative pathogens.

Even within those limits, the work lands at a compelling moment. Humic substances are already used in agriculture as soil conditioners and fertilizers, added to animal feed to improve growth and immunity, and investigated as anti-inflammatory, antitumor, and wound-healing agents. If subsequent research confirms that fulvic acid’s antimicrobial effects survive purification, formulation, and contact with living systems, a substance that farmers currently discard, or that poses a disposal and sanitation burden in much of the developing world, could be converted into a feedstock for natural antimicrobials. The road from a petri dish in Khairpur to a clinic or a feed additive is long, and the required in vivo studies, toxicity evaluations, and resistance testing will take years. But the underlying idea, that the answer to drug-resistant bacteria might be composting at the edge of the village, is exactly the kind of cross-disciplinary leap that the antimicrobial resistance crisis demands, and this study offers the first careful, spectroscopically verified evidence that the leap is worth taking.

Subject of Research: Antimicrobial activity of fulvic acid extracted from cow dung against Gram-negative bacteria

Article Title: Antimicrobial activity of fulvic acid extracted from bovine dung against selected gram-negative pathogens: a preliminary in vitro assessment

Article References: Chachar, Z. A., Dharejo, S. A., & Pirzada, T. (2026). Antimicrobial activity of fulvic acid extracted from bovine dung against selected gram-negative pathogens: a preliminary in vitro assessment. Discover Chemistry, 3(1), Article 548. https://doi.org/10.1007/s44371-026-00935-8

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00935-8

Keywords: fulvic acid, cow dung, antimicrobial resistance, Gram-negative bacteria, Escherichia coli, Pseudomonas aeruginosa, Salmonella Typhi, humic substances, FTIR spectroscopy, X-ray diffraction, minimum inhibitory concentration, natural antimicrobials

The research team, led by Wenjing Wang and colleagues, searched PubMed, Scopus, and Web of Science for studies published since 2014, applying the rigorous standards of the PRISMA reporting framework and registering the protocol prospectively with PROSPERO under registration number CRD42025648170. Their aim was deceptively simple but methodologically demanding: to estimate pooled incidence and prevalence of urinary tract infections across different healthcare settings, and then to dissect those estimates by geography, infection setting, and host risk profile. The final dataset included 969,476 participants, a scale that lends considerable statistical weight to the pooled estimates.

The headline finding concerns the stark divide between hospital-acquired and community-acquired infections. Hospital-acquired urinary tract infections, abbreviated HAUTIs in the study, showed a pooled incidence proportion of 0.17, with a 95 percent confidence interval of 0.13 to 0.22, and a pooled prevalence of 0.21, with a confidence interval of 0.16 to 0.25. By comparison, community-acquired urinary tract infections showed a pooled incidence of just 0.08, with a confidence interval of 0.06 to 0.10. In practical terms, roughly one in five hospitalised patients in the included studies had or acquired a urinary tract infection, a figure that underscores how the hospital environment itself, with its invasive devices, immunocompromised patients, and dense microbial ecology, amplifies infection risk.

Within the hospital setting, the single most dangerous factor identified was the urinary catheter. Catheter-associated urinary tract infections emerged as a particularly high-risk category, which is consistent with the well-understood biology of these devices. An indwelling catheter provides bacteria with a direct conduit into the bladder, bypassing the natural flushing action of urination and forming a biofilm on its surface that shields microbes from both immune defences and antibiotics. The meta-analysis confirms that this device-related pathway remains a dominant driver of nosocomial urinary infection, and that catheter stewardship, meaning the avoidance, early removal, and meticulous management of urinary catheters, must sit at the centre of any prevention strategy.

Geography mattered as much as setting. The burden of hospital-acquired urinary tract infections was highest in Asia, Africa, and South America, a pattern that likely reflects a combination of factors including differences in healthcare infrastructure, catheterisation practices, antibiotic access, and surveillance capacity across regions. The authors argue that this regional variation exposes a central weakness in current infection control thinking: a uniform, one-size-fits-all prevention approach cannot adequately serve settings whose baseline risks, resources, and microbial ecologies differ so dramatically. Tailored protocols calibrated to local epidemiology, they suggest, are the realistic path forward.

On the microbiological front, the analysis confirmed what clinical microbiologists have long observed: gram-negative bacteria, and particularly Escherichia coli, dominate the etiology of urinary tract infections. Escherichia coli’s specialised adaptations for the urinary tract, including adhesive pili that bind to bladder epithelial cells and an ability to persist intracellularly, make it an exceptionally effective uropathogen. The predominance of gram-negative organisms carries practical consequences, because rising antimicrobial resistance in this bacterial group, particularly extended-spectrum beta-lactamase production, increasingly constrains empiric treatment choices in many regions.

Beyond setting and geography, the study systematically catalogued host-level risk factors, identifying gender, age, comorbidities, and prior disease history as consistent predictors of infection. Some of the most striking quantitative results came from specific vulnerable populations. Among kidney transplant recipients, those who experienced delayed graft function, a complication in which the transplanted kidney does not immediately work properly, faced a risk ratio of 1.63 for urinary tract infection, with a confidence interval of 1.19 to 2.22. This makes biological sense: impaired graft function alters urinary flow and immune regulation, and transplant patients are simultaneously subjected to immunosuppressive drugs that blunt their defences against bacterial invasion.

Pregnant women formed another clearly delineated high-risk group. The analysis found that lower educational attainment among pregnant women was associated with an elevated risk of urinary tract infection, with a pooled effect estimate of 0.40 and a confidence interval of 0.16 to 0.63. Pregnancy itself predisposes to urinary infection through hormonal relaxation of the ureters and mechanical compression of the urinary tract by the growing uterus, which slows urine flow and allows bacteria more time to establish themselves. Untreated infections in pregnancy can escalate to pyelonephritis and are associated with adverse outcomes for both mother and fetus, which is why identifying modifiable social determinants of risk, such as access to health education, carries real public health value.

The study also highlighted the elderly and people with diabetes as key vulnerable groups. Diabetes impairs immune function and, when poorly controlled, glycosuria creates a nutrient-rich environment in the urine that favours bacterial growth. Ageing, meanwhile, brings anatomical and physiological changes, incomplete bladder emptying, and higher rates of catheterisation and institutional care, all of which compound infection risk. By quantifying these risks within a single analytical framework, the review provides clinicians and policymakers with a stratified map of exactly where preventive effort should be concentrated, rather than spreading resources thinly across the entire patient population.

The broader significance of this work lies in its framing. Rather than treating urinary tract infections as a single homogeneous disease, the authors demonstrate that the burden is sharply stratified by where a patient is treated and who the patient is. That insight supports the development of risk-stratified infection control protocols: aggressive catheter reduction programmes and surveillance in hospitals, targeted screening and education for pregnant women, heightened vigilance in transplant units, and tailored prevention for diabetic and elderly patients. As antimicrobial resistance narrows the treatment options available for gram-negative uropathogens, preventing infections in the first place becomes not merely a convenience but a necessity. This meta-analysis, synthesising evidence from nearly a million people across continents and care settings, offers the clearest evidence yet of where that prevention effort must be aimed.

Subject of Research: Global epidemiology and risk-stratified burden of urinary tract infections across healthcare settings and high-risk populations

Article Title: Risk-stratified epidemiology and global burden of urinary tract infections across healthcare and high-risk populations: a systematic review and meta-analysis

Article References: Wang, W., Huo, N., Ma, H., Li, X., & Wang, Y. (2026). Risk-stratified epidemiology and global burden of urinary tract infections across healthcare and high-risk populations: a systematic review and meta-analysis. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14395-z

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14395-z

Keywords: urinary tract infection, hospital-acquired infection, catheter-associated UTI, meta-analysis, Escherichia coli, kidney transplant, pregnancy, diabetes, infection control, antimicrobial resistance, global health burden, risk factors

The mathematical backbone of the work is elegantly simple. Many celebrated indices in chemical graph theory, including the Zagreb indices, the Randić index, Sombor-type measures, the Albertson irregularity index, arithmetic-geometric and geometric-arithmetic indices, the Forgotten index and inverse Nirmala indices, can all be written as a sum over the edges of a molecular graph of a symmetric function of the degrees of the two atoms joined by each bond. The authors multiply each of these contributions by a normalisation factor derived from the general sum-connectivity index introduced by Zhou and Trinajstić: the weight one over the square root of the sum of the two endpoint degrees. Because this factor decreases as the local connectivity increases, it moderates the dominance of edges attached to high-degree atoms, a known source of instability when classical descriptors are applied across chemically diverse datasets.

The framework is not merely a numerical tweak. The authors prove a set of structural results that give the new family a rigorous footing. For any molecular graph whose minimum and maximum vertex degrees are delta and capital delta respectively, each sum-connectivity descriptor is provably sandwiched between its classical counterpart scaled by one over the square root of twice capital delta and the same counterpart scaled by one over the square root of twice delta. On regular graphs, where every atom has the same degree, the relationship collapses to exact proportionality with a constant of one over the square root of two r. The paper further derives explicit min-max bounds for representative descriptors in terms of the number of edges and the degree extremes, develops complement-graph identities showing how the reweighting behaves under the transformation that maps each degree to n minus one minus the original degree, and introduces a ‘hyper sum-connectivity’ index obtained when the construction is applied to the classical sum-connectivity index itself.

To test whether this theory translates into predictive power, the team assembled a carefully curated antibacterial dataset from the ChEMBL bioactivity database, restricted to minimum inhibitory concentration measurements against Escherichia coli, an organism that is both a common member of the human microbiome and a leading cause of urinary tract, bloodstream and intra-abdominal infections increasingly complicated by multidrug resistance. After standardising all MIC values to micromolar units, aggregating duplicates by median and expressing potency as the negative base-ten logarithm, the final dataset comprised 6,657 unique compounds, each characterised by eight physicochemical properties, two blocks of fourteen topological indices, the classical family and the new sum-connectivity family, and a block of ninety RDKit descriptors capturing size, branching, ring content and related structural features.

The first empirical test was a deliberately controlled one: a head-to-head comparison of the two index families alone across eight physicochemical endpoints, with everything else held constant. Under a demanding five-times-repeated five-fold cross-validation protocol, the sum-connectivity family produced higher mean coefficients of determination for all eight targets, lifting the average R-squared from 0.6951 for the classical indices to 0.7015 for the reweighted ones. The gains were most visible for topological polar surface area, lipophilicity and the spacial score, while molecular weight barely moved. The authors are careful to characterise this as a modest but systematic improvement, a claim backed by the theoretical guarantees rather than by an isolated lucky result.

A second, broader QSPR experiment concatenated everything: RDKit descriptors, both index families and the physicochemical properties, into a single ‘All Combined’ feature set. This configuration delivered the highest scores of the study, with R-squared values ranging from 0.9349 for NP-likeness to 0.9997 for molecular weight. But the team resists the temptation to oversell these numbers. Correlation analyses reveal that several endpoints are almost directly encoded by closely related features already present in the pool: molecular weight correlates with the RDKit exact molecular weight at a Spearman coefficient of 0.99999, and topological polar surface area tracks the nitrogen-oxygen count at 0.9304. The near-unity scores are therefore best read as upper-bound benchmarks within the available descriptor space, not as proof of independent mechanistic insight. A sensitivity rerun with principal component compression lowered scores across the board, showing that blind dimensionality reduction is no substitute for careful proxy-descriptor removal.

The harder test was antibacterial activity itself. Predicting the pMIC endpoint from structure alone is intrinsically difficult because potency reflects a tangle of scaffold class, charge distribution, lipophilicity, hydrogen-bonding profile and, often, a specific mechanism of action that no purely topological number can see. The best-performing QSAR model was an Extra Trees regressor trained on RDKit descriptors, reaching an R-squared of 0.5959 plus or minus 0.0246 under repeated cross-validation. Critically, the team then repeated the evaluation using a far stricter Murcko scaffold-based validation, which keeps close structural analogues out of the training folds and probes whether models generalise to genuinely new chemotypes. Performance dropped, as expected, to an R-squared of 0.4799 plus or minus 0.0252, but the ranking of feature families remained stable, indicating reproducible rather than chance-driven signal.

Within that stricter landscape, the new descriptors tell an honest story. On their own, the standalone sum-connectivity indices edged out the classical family for pMIC prediction, 0.2887 versus 0.2767 under random cross-validation and 0.2025 versus 0.2019 under scaffold validation, but both were clearly weaker than the rich RDKit representation, and the sum-connectivity advantage effectively disappeared once RDKit features were present. Diagnostics on the best model reinforced the picture of genuine but moderate predictability: a Y-randomization test with fifty permutations produced a mean R-squared of minus 0.0356, separated from the real model by a Z-score of 91.8, while permutation importance highlighted heterocycle counts, aliphatic ring content, charge-sensitive surface-area terms and electronic-state measures, a chemically plausible fingerprint of the determinants of antibacterial potency. A learning curve still rising with training-set size suggests further curated data would continue to help.

The study’s conclusions are notably measured for a field where bold claims are common. The authors state plainly that their descriptors are most strongly supported as systematically improved graph-topological descriptors in matched comparisons, with added value for the heterogeneous pMIC endpoint that is complementary and modest. They also acknowledge that every classical index is almost collinear with its sum-connectivity counterpart, with Spearman correlations between 0.9967 and 0.9986, and that a PCA rerun reduced the strongest benchmark scores while leaving constitution-driven targets comparatively easy to encode, so targeted removal of proxy descriptors and regularised feature selection remain the more promising next steps.

For the wider cheminformatics community, the work offers a template as much as a tool. It shows how a single, mathematically transparent transformation can generate a coherent descriptor family with provable bounds, how controlled matched benchmarks should be separated from headline-grabbing combined-model scores, and how scaffold-based validation should be the default standard for activity modelling on real drug-discovery data. The mathematical side also leaves a clear opening: extending the reweighting to the general chi-alpha family and studying how the exponent on the degree sum affects extremal behaviour and descriptor discrimination is flagged as an open direction. In an era when machine learning models are only as trustworthy as the features fed into them, a rigorous attempt to make one small corner of the descriptor space measurably better is a quietly consequential contribution.

Subject of Research: Sum-connectivity molecular descriptors for QSPR and antibacterial QSAR modelling

Article Title: Advancing QSPR with sum-connectivity descriptors: physicochemical and antibacterial modelling via molecular graph connectivity

Article References: Altairi, A., Alsharafi, M., & Alhaj, Z. (2026). Advancing QSPR with sum-connectivity descriptors: physicochemical and antibacterial modelling via molecular graph connectivity. Journal of Saudi Chemical Society, 30(4), Article 50. https://doi.org/10.1007/s44442-026-00105-6

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00105-6

Keywords: QSPR, QSAR, topological indices, sum-connectivity descriptors, molecular graphs, antibacterial activity, Escherichia coli, ChEMBL, machine learning, MIC prediction, chemical graph theory, RDKit

The research team, working under the ethical approval of the Bangladesh Livestock Research Institute, collected 400 pooled fecal samples from commercial poultry farms across four districts: Dhaka, Tangail, Mymensingh, and Sylhet. The sampling strategy deliberately spanned the three major poultry production systems in the country, with 160 samples each from broiler and layer farms and 80 from Sonali farms, a locally important dual-purpose breed. Each composite sample was gathered from five separate locations within a single farm, then pre-enriched in buffered peptone water and cultured on selective media. Molecular confirmation by polymerase chain reaction targeting the 16S rRNA gene identified E. coli in 280 of the 400 samples, a striking 70 percent detection rate that underscores how pervasive the organism is in these production environments.

Antimicrobial susceptibility testing against twelve antibiotics from nine classes revealed alarming phenotypic patterns. Resistance to ampicillin reached 97.86 percent, tetracycline resistance stood at 97.50 percent, and trimethoprim-sulfamethoxazole resistance was recorded at 91.79 percent, while nearly 69 percent of isolates resisted ciprofloxacin, a fluoroquinolone classified as critically important for human medicine. Only imipenem, a last-resort carbapenem, retained high effectiveness, with 96.43 percent of isolates remaining susceptible. These figures reflect decades of unrestricted over-the-counter antibiotic availability in Bangladesh, where antimicrobials have long been used as growth promoters and prophylactic agents, creating sustained selective pressure that favors the emergence and persistence of multidrug-resistant strains.

From this collection, the researchers selected three multidrug-resistant isolates, one from each production system, for whole-genome sequencing on an Illumina NextSeq 2000 platform. The sequencing generated roughly 8.2 to 9.8 million paired-end reads per isolate, achieving approximately 300-fold coverage. Assembled genome sizes ranged from 4.4 to 5.4 megabases with GC contents between 50 and 51 percent. These three genomes were then compared against 83 publicly available genomes from NCBI GenBank, drawn from poultry, human, and environmental sources across the world, producing a comparative dataset of 86 genomes designed to place the Bangladeshi isolates within a genuinely global context.

The resistance gene analysis revealed dense and varied arsenals. The layer isolate proved the most heavily burdened, harboring blaCTX-M-15, blaOXA-1, blaTEM-1B, qnrS1, sul2, sul3, tet(A), tet(M), and aac(6′)-Ib-cr, a combination conferring resistance across beta-lactams, fluoroquinolones, sulfonamides, tetracyclines, and aminoglycosides through mechanisms including antibiotic inactivation, target protection, target alteration, and efflux. The broiler isolate carried blaCTX-M-27 alongside floR, cmlA7, aph genes, dfrA14, sul2, and tet(A), while the Sonali isolate combined blaCTX-M-15 and blaTEM-1B with mph(A), qnrS1, sul3, and dfrA14. The CTX-M family of extended-spectrum beta-lactamases, particularly CTX-M-15 and CTX-M-27, is among the most clinically consequential resistance determinants worldwide, and its consistent presence in poultry-associated isolates signals a reservoir of genes with direct human health implications.

Country-level comparison using the Jaccard similarity index showed that the Bangladeshi isolates shared the highest average AMR gene profile similarity with isolates from Japan at approximately 0.32, followed by South Korea and Norway at around 0.30, with lower similarity to isolates from Argentina, Cambodia, Vietnam, and India. At the individual strain level, the closest matches were strain 45E from Switzerland with a similarity of 0.55, strain 1500 from Norway at 0.50, and EC10 from Italy at 0.49. While these values are moderate rather than close, they indicate that the resistance gene content of the Bangladeshi poultry isolates overlaps meaningfully with globally distributed strains rather than representing an isolated local phenomenon.

Virulence gene profiling painted an equally detailed picture. All three isolates carried the conserved fimbrial adhesin cluster fimA through fimI and curli-associated genes csgA through csgC, indicating strong colonization capacity. The broiler isolate carried the largest virulence repertoire, including extensive type II and type VI secretion system genes, the invasion-associated ibeB and ibeC genes, a full kps capsule gene cluster, and ompA. The layer isolate showed a reduced set dominated by adhesion and iron acquisition genes, including the yersiniabactin system, while the Sonali isolate displayed an intermediate profile with additional immune modulation genes gndA and gtrA. Shared virulence genes with global isolates were highest for Italy at roughly 110 genes, China and Japan at around 109 and 108, and the United States at 108, while Jaccard similarity of virulence profiles peaked with Norway at 0.63, Vietnam at 0.60, and Pakistan at 0.59. A conserved core of adhesion, motility, iron acquisition, and regulatory genes, including fur, phoP, pmrA, rcsB, and rpoS, was present across all three isolates, reflecting the stable machinery required for host adaptation.

Plasmid analysis added another layer of complexity. The broiler isolate harbored the most elaborate plasmid architecture, carrying Col(pHAD28), Col440I, IncFIB, and IncFIB(pLF82) replicon types, a family of plasmids well recognized as major vehicles for the co-dissemination of resistance and virulence genes. The layer isolate carried Col(MG828), IncFIB, and IncFIC(FII), while the Sonali isolate carried only IncX1, the simplest profile. Plasmid profile similarity with global strains was highest for Denmark at approximately 0.40 and the Philippines at 0.39, and lowest for India, Thailand, the United Kingdom, and Germany, underscoring the heterogeneous and regionally variable nature of plasmid content. Because IncF-type plasmids are notorious for linking multiple resistance genes onto single mobile elements, their prominence raises concerns about co-selection, in which the use of any single antibiotic can maintain an entire multidrug resistance payload.

Pangenome analysis across the three poultry isolates identified 7550 gene clusters, of which 2238, or 29.6 percent, were core genes shared by all three, while the remaining 70.4 percent formed the accessory genome, with the layer isolate alone contributing 5078 unique genes. Scaling up to the full 86-genome dataset revealed a pangenome of 29,366 gene clusters with only 4.6 percent core genes and nearly 80 percent cloud genes, a signature of the famously open pangenome of E. coli, which expands continuously as new genomes are added. Multilocus sequence typing assigned all three Bangladeshi isolates to sequence type ST457, a type also reported in Italy. In the minimum spanning tree, ST457 sat within a central clonal complex connected to globally dominant lineages including ST10, ST167, ST648, and the notorious ST131, which was documented across Argentina, Denmark, Italy, Malaysia, the United Kingdom, and the United States in the comparison dataset.

The authors caution that the small number of sequenced Bangladeshi isolates, the heavily fragmented assembly of the layer isolate, and the absence of simultaneously sampled human and environmental isolates limit direct inference of transmission routes. The genetic similarity with international strains indicates shared ancestry and gene exchange patterns rather than proven transmission. Nevertheless, the study delivers a clear message: poultry production systems in Bangladesh harbor E. coli carrying clinically relevant resistance and virulence determinants embedded in globally connected lineages. Strengthening antimicrobial stewardship in veterinary sectors, improving farm-level biosecurity, and building integrated One Health surveillance that links human, animal, and environmental sampling are highlighted as urgent priorities to interrupt the circulation of these genes before their passage into the food chain and human populations becomes still more efficient.

Subject of Research: Comparative genomics of multidrug-resistant poultry-associated Escherichia coli in Bangladesh

Article Title: Comparative Genomic Analysis of Multidrug‐Resistant Escherichia coli Across Poultry–Human–Environmental Interfaces

Article References: Shanto, M. R. H., Ashab Uddin, A. S. M., Supto, M. S. M., Mahim, N. J., Howlader, M. M. R., Ahmed, S. S. U., & Uddin, M. B. (2026). Comparative Genomic Analysis of Multidrug‐Resistant Escherichia coli Across Poultry–Human–Environmental Interfaces. MicrobiologyOpen, 15(5), Article e70406. https://doi.org/10.1002/mbo3.70406

Image Credits: AI Generated

DOI: 10.1002/mbo3.70406

Keywords: antimicrobial resistance, Escherichia coli, whole-genome sequencing, poultry, Bangladesh, pangenome, blaCTX-M, virulence genes, plasmids, ST457, One Health, genomic surveillance