The gut microbiome of social bees is a small, specific set of symbionts that contributes to nutrition, detoxification, immune function and behaviour, with effects on colony performance and resilience. In recent years, the field has expanded, but studies still analyse host genetics and environmental exposures separately and often rely on correlations between microbes and health traits. This makes it difficult to distinguish between instances in which microbiome differences primarily reflect host or environmental factors and instances in which they may contribute mechanistically to bee health. A key challenge is context dependence: similar microbiome shifts may be associated with different trait outcomes depending on life stage and task, exposure history, and colony transmission structure. We present the Genome Exposome Microbiome–Phenome (GEM–P) framework as an integrative organisational framework for social bees. GEM–P treats genome, lifetime exposures (exposome), and the gut microbiome as interacting components shaping phenotypes at both individual and colony scales. Phenotypes can, in turn, modify subsequent exposures and microbiome states. We use GEM–P to map evidence on genetic filtering, exposomal drivers, microbiome assembly and function, and phenotypic outcomes, and to highlight study designs that help distinguish among alternative biological pathways without requiring comprehensive multi-omics approaches. GEM–P provides a practical way to generate pathway-specific hypotheses and interpret microbiome–phenotype associations across contexts. • An integrative framework linking genome, exposome, gut microbiome, and phenome in social bees. • Highlights scale, timing, and social transmission as sources of context dependence. • Supports pathway-specific hypotheses and sampling designs that help distinguish alternative explanations for microbiome–phenotype associations.
Thiosulfate citrate bile salts sucrose (TCBS) agar is a widely used selective medium for the presumptive isolation of Vibrio spp, playing an essential role in food safety and public health surveillance. However, variations among commercial formulations may significantly affect detection accuracy. In this study, seven commercial TCBS agar formulations were systematically evaluated for their ability to support the growth and colony development of Vibrio cholerae and Vibrio parahaemolyticus strains, and inhibition of non-target bacteria. The effects of pH, as well as the source and concentration of bovine bile salts, on medium performance were also investigated. The results revealed significant differences among formulations in the recovery of the tested V. cholerae and V. parahaemolyticus strains and in selectivity against non-target bacteria. Media with stronger inhibition of competing bacteria generally exhibited reduced recovery of target Vibrio, indicating a trade-off between sensitivity and specificity. Both the source and concentration of bile salts influenced medium performance. Alkaline conditions (pH 8.4–9.2) supported recovery of the two target Vibrio species while improving inhibition of non-target bacteria. Collectively, this study provides experimental data on performance variability among commercial TCBS agar formulations and offers useful insights for improving the reliability of presumptive isolation of the two target species and informing TCBS agar optimization.
The efficient selection of cell lines that produce high levels of therapeutic proteins is a major challenge in biotechnology. The glutamine synthetase (GS)-based selection system, widely used in Chinese hamster ovary (CHO) cells, is limited in its ability to isolate rare high-producing clones due to the intrinsic stability of the GS protein. This stability lowers selection stringency, allowing survival of cells with suboptimal productivity. To address this limitation, we engineered GS variants incorporating modular degrons to actively regulate protein degradation and intracellular GS levels. This strategy increases selection pressure by controlling protein stability, rather than relying on transcriptional or translational regulation. In CHO cells expressing either a reporter protein or Etanercept (ETN), destabilized GS (dGS) variants selectively enriched cell pools with markedly enhanced productivity. Molecular analysis revealed that these improvements were driven by increased per-copy mRNA abundance, rather than gene copy amplification. The top-performing dGS pool achieved an ETN titer of 870 mg/L in shake-flask batch culture and maintained stable production over 80 days of passaging. Notably, these results were obtained without chemical selection agents or extensive gene amplification. Collectively, this study demonstrates that proteostasis engineering—modulating the balance between protein synthesis and degradation—enables high-stringency, drug-free selection of high-producing cell lines. This approach has the potential to accelerate cell line development and reduce manufacturing complexity in biopharmaceutical production. • Degradable GS variants increase selection stringency by accelerating GS protein turnover. • Degradable GS selection enriches high producers via elevated per-copy transcript output. • Drug-free dGS pools achieved 870 mg/L Etanercept titer in batch culture.
The microbial consortium of Fructilactobacillus sanfranciscensis and Maudiozyma humilis is associated with complex trophic interactions that support persistence in sourdough ecosystems. However, its stability may depend on technological parameters, including dough yield, flour type, backslopping conditions and refreshment regime. This study assessed the long-term stability of this consortium in two wholemeal wheat mother sourdoughs from Belgian industrial bakeries, referred to as IB-A and IB-B. These sourdoughs differed in dough yield, namely 160 for IB-A and 200 for IB-B, and in backslopping conditions. Both sourdoughs were subjected to weekly or triweekly refreshment cycles, each combining cold storage at 4 °C with backslopping at either room temperature for 24 h or 30 °C for 16 h. Under weekly refreshment, the consortium persisted for one month in both sourdoughs. Under triweekly refreshment, Frul. sanfranciscensis and Maud. humilis remained stable only in IB-A, whereas both species were lost from IB-B after 12 and 15 weeks, respectively. In IB-B, Levilactobacillus parabrevis and Pediococcus parvulus became prevalent. In contrast, stable production of acetic acid, ethanol, and mannitol in IB-A indicated sustained metabolic activity of the Frul. sanfranciscensis–Maud. humilis consortium. These findings show that the long-term viability and metabolic fitness of this consortium require suitable combined process parameters.
Probiotic efficacy depends not only on gastrointestinal survival but on mucosal adhesion and the capacity to deliver bioactive molecules at the intestinal surface. This study optimized a whey protein isolate (WPI)–chitosan (CS) matrix for spray drying microencapsulation of Lacticaseibacillus casei BL23 using central composite design, targeting enhanced mucoadhesion while preserving bacterial viability and extracellular vesicle (EV) secretion capacity. The optimal formulation, WPI 20
Saccharomyces cerevisiae yeast is a widely used recombinant protein production host. Recombinant protein expression requires adaptation of the host cell proteome to accommodate the increased biosynthetic and folding demands. However, this underlying proteomic changes remain poorly understood. In this study, we quantified the proteome of a laboratory S. cerevisiae strain over four days during batch cultivation for recombinant laccase production to characterize the resulting proteomics remodeling. Whereas a substantial portion of the proteome changed in response to nutrient depletion during batch growth, only a smaller subset of proteins was affected by laccase expression. By comparing yeast strains of different origins and laccase production capacities, we found that each strain displayed a distinct response to heterologous expression, regardless of the origin of the laccase. For example, the chaperones Hsp26 and Kar2 were specifically elevated in a whey-derived strain upon laccase expression. Nonetheless, the higher capacity to produce active recombinant laccase in some strains appears to be associated primarily with small groups of proteins that are constitutively expressed at different levels. These results indicate that strains of different origins each provide a unique cellular milieu that, in some cases, is more favorable for the expression of a given recombinant protein. This study provides the first insights into the dynamic proteome remodeling that occurs during recombinant laccase expression and highlights the potential of exploiting naturally occurring yeast diversity, rather than relying solely on strain engineering, to improve recombinant protein yields. • Proteomes of S. cerevisiae strains during recombinant laccase expression determined • Ribosomal and metabolic protein levels change during recombinant expression • Unique cellular milieu, rather than proteome shifts, is linked to higher yields
Protein-glutamine glutaminase (PGG) is a promising enzyme for improving the functionality of plant proteins, but its industrial production is limited by low native yields and the need for proteolytic activation. Here, we developed a standardized modular Golden Gate-based secretion platform in Bacillus subtilis to screen promoter-signal peptide combinations for extracellular production of Chryseobacterium proteolyticum PGG (CpPGG) within a common construct architecture. Reporter and enzyme-based screening identified Pgrac100-amyQ* as the configuration that consistently supported robust secretion and functional CpPGG production in B. subtilis 168, where the secreted proenzyme underwent host-mediated maturation. In 3-L batch bioreactor cultivation in rich medium, this construct reached 2.9 U/mL of supernatant (SN), whereas fed-batch cultivation in defined medium revealed extracellular proteolysis as a major limitation under high-cell-density conditions. To decouple secretion from activation, the construct was transferred to the protease-deficient strain KO7-S which enabled stable accumulation of non-processed CpPGG. Subsequent controlled in vitro activation with a food-grade neutral protease yielded 12.8 ± 0.8 U/mL SN. Together, these results show that efficient PGG production in B. subtilis requires coordinated control of secretion, extracellular stability and proenzyme activation. • Modular screening identified Pgrac100-amyQ* for CpPGG secretion in B. subtilis. • Proteolysis limited high-cell-density fed-batch production in B. subtilis 168. • In Bs KO7-S, secretion and activation were decoupled yielding 12.8 ± 0.8 U/mL SN.
The transition toward a circular bioeconomy relies on identifying microorganisms with traits suitable for sustainable industry. This study explored the biotechnological potential of two Papiliotrema laurentii strains isolated from contrasting environments: urban São Paulo (FBU001) and the Atacama Desert (FBU003). The research focused on the safety profile of the strains, environmental stress resistance, and ability to produce photoprotective compounds. Taxonomic identity was confirmed through ribosomal DNA sequencing and MALDI-TOF Biotyper. Crucially, biosafety assessments, including growth temperature limits and the absence of common fungal virulence factors, combined with in vivo infection models, indicated that both strains have low pathogenic potential and are safe for industrial applications. Physiological tests showed that while both strains resist UVC radiation, the Atacama strain possesses additional extremophilic adaptations like osmotic stress tolerance. Both yeasts produced mycosporine-glutaminol (MG), a natural antioxidant and UV filter. Genomic and transcriptional analyses confirmed that the genes responsible for this compound are organized in a cluster (MYC BGC) activated by UV exposure, suggesting that MG production is a conserved trait in the species regardless of its habitat. These findings position these yeasts as robust candidates for sustainable biotechnology. By offering a bio-based alternative to synthetic sunscreen ingredients, this work supports the development of renewable, biodegradable cosmetics within a circular bioeconomy framework. • P. laurentii from diverse geographic origin are avirulent and produce MG under UVR. • P. laurentii from the Atacama Desert are highly resistant to multiple stress factors. • MYC BGC transcription is UVR induced and it is associated with the production of MG.
Heavy metals (HMs) are naturally occurring elements which can be essential, such as zinc, copper, and iron, or non-essential, including cadmium, mercury, and lead. While essential metals serve as cofactors in critical enzymatic processes, elevated concentrations of both essential and non-essential HMs pose severe toxicity risks, primarily through oxidative stress, disruption of metal homeostasis, and biomolecular damage. Microorganisms have evolved diverse mechanisms to cope with metal-induced stress, including metal sequestration, enzymatic transformation, efflux systems, and surface immobilization. Among these, metallothioneins (Mts) are small, cysteine-rich proteins capable of high-affinity metal binding, contributing to cellular detoxification. Although Mts have been extensively studied in eukaryotes, knowledge of bacterial Mts remains limited, with characterized examples largely confined to cyanobacteria and a few other bacterial species. In this study, we identified a novel hybrid protein, TrxA, from Runella aurantiaca, containing a thioredoxin (Trx) domain fused to a Mt domain. The presence of the Trx domain may confer improved stability and solubility, supporting potential recombinant applications. In fact, the recombinant protein, named TrxMt, was heterologously expressed in Escherichia coli, displaying both disulfide-reducing activity and heavy metal–binding capability. Notably, TrxMt expression enhanced bacterial tolerance to multiple HMs, demonstrating its functional relevance in vivo. These findings expand the understanding of bacterial Mt diversity and suggest that TrxMt is a promising candidate for the bioremediation of heavy metal–contaminated environments, combining metal detoxification with favorable biochemical properties for industrial and environmental applications. • Identification of TrxA, a novel hybrid thioredoxin–metallothionein in R. aurantiaca • Recombinant protein TrxMt shows reductase activity and binds HMs • Overexpression of TrxMt enhances tolerance to different HMs in E. coli
Fibrillar type III collagen, characterized by a distinct triple helix structure, is a critical structural component of the mammalian extracellular matrix (ECM). Its unique mechanical properties and biological functions make it a highly valuable biomaterial for medical applications. However, the limited availability of natural human type III collagen (hCOL3) and the defects of animal-derived sources necessitate sustainable alternatives. Here, we developed an integrated molecular engineering strategy for the efficient production of full-length recombinant human type III collagen (rhCOL3) in Komagataella phaffii. The N- and C-terminal propeptides of the rhCOL3α1 chain were rationally redesigned to preserve its intrinsic capability for triple helix formation. Synergistic co-expression of human P4Hαβ and Bacillus anthracis-derived BaP4H achieved a proline hydroxylation level of 52.88
Long-chain hydrocarbon biodegradation is limited by its low bioavailability. Specific strains degrade hydrocarbons including long-chain alkanes. Rhodococcus erythropolis ICBD2 is a hydrocarbonoclastic bacterium isolated from a chronically petroleum-contaminated coastal soil from Valparaiso Region, Central Chile. The aims of the study were the characterization of catabolic genes and the adaptation of the membrane, cell wall, morphology, and metabolism of R. erythropolis ICBD2 to long-chain alkane n-eicosane. Genes encoding alkane monooxygenases involved in the degradation of different chain length alkanes (five alkB, almA, and ladA), cytochrome monooxygenases (seven cyp), and Baeyer–Villiger-type monooxygenases (ethA, pamO and PA1538) are distributed in ICBD2 genome. R. erythropolis ICBD2 showed significant growth (turbidity600nm 1.0) on n-eicosane (5 mM) as sole carbon and energy source. ICBD2 cells grown on n-eicosane reduced the cellular surface area and increased hydrophobicity compared to acetate-grown bacteria. In comparison with acetate-grown cells, bacteria grown on n-eicosane increased the saturation and reduced the chain length of their membrane fatty acids (FA) and cell wall mycolic acids (MA), resulting in a more rigid and stable cellular structure. During growth on n-eicosane, strain ICBD2 increased the expression of alkB1, alkB2, and almA catabolic genes and reduced the expression of kasAB gene associated with the elongation of fatty acids. Remarkably, in this study we presented for the first time the adaptive response of Rhodococcus to growth on a long-chain alkane both at structural and metabolic levels. The results are useful to uncover Rhodococcus mechanisms of adaptation to long-chain alkanes, which are crucial for bioremediation of low bioavailable petroleum hydrocarbons. • n-Eicosane increases hydrophobicity and hydrocarbon adhesion of Rhodococcus cells • n-Eicosane increases saturation and decreases lengths of membrane FA and cell wall MA • In strain ICBD2, n-eicosane induced the expression of alkB1, alkB2, and almA genes
The WalRK two-component system monitors cell wall biosynthesis, and its activity decreases when biosynthesis is inhibited. As WalRK is essential for many Gram-positive bacteria, including Staphylococcus aureus and Bacillus subtilis, directly inhibiting WalK would disrupt cell wall biosynthesis and result in cell death. This study presents the construction of new reporter strains with two WalRK-dependent promoters: PiseA and PssaA. These reporter strains enable indirect in vivo measurement of WalRK activity based on luminescence. We evaluated these reporters in combination with the established PliaI reporter system, which is regulated by LiaRS, in order to improve the identification of cell wall inhibitors during the screening of natural products. The WalRK-dependent PiseA reporter yielded specific responses to almost all known cell wall biosynthesis inhibitors, including β-lactams, tunicamycin, glycopeptides, daptomycin, and fosfomycin, with no discernible response to other antibiotic classes. Furthermore, combining the PliaI reporter system with the PiseA reporter enhanced the range of potential cell wall inhibitors that could be detected. Deleting the gene of the eukaryotic-like Ser/Thr kinase PrkC increased the PiseA signal obtained with certain antibiotics, as well as after a longer incubation period. Additionally, deletion of prkC lowered PliaI expression in the presence of lipid II-targeting antibiotics. Screening natural products with an unknown mode of action identified several compounds that elicited vancomycin-like patterns with the reporter systems, indicating potential cell wall inhibitory activity. Overall, combining WalRK and LiaRS reporters enables a rapid, complementary evaluation of cell wall stress responses, providing a powerful method for discovering new cell wall-targeting antibiotics. • The PiseA/PssaA reporters enable continuous in vivo observation of WalRK activity • Cell envelope stress responses are differentially sensed by WalRK and LiaRS • The PiseA reporter strain detects nearly all cell wall biosynthesis inhibitors
The Chinese hamster ovary (CHO) cell line is a predominant host for the production of biopharmaceuticals due to its high capacity for recombinant protein production. However, limitations in protein secretion remain a challenge. In this study, we combined transcriptomic sequencing and fed-batch screening to identify the cytoplasmic poly(A)-binding protein gene, Pabpc1, as a positive regulator of recombinant protein expression. Stable overexpression of Pabpc1 in CHO cells producing monoclonal, bispecific, and trispecific antibodies enhanced protein titers by 30–50
Bioreduction of prochiral N-(3-oxobutyl)- and N-(2-oxopropyl)heterocycles—comprising (partially) saturated, flexible rings—was explored, using microbial whole-cell ketoreductases, including selected wild-type yeast strains and enantiocomplementary recombinant alcohol dehydrogenases (ADHs). Initial screening reactions with yeast strains resulted in (S)-alcohols with low to moderate conversions. Optimization of the reaction conditions (substrate and cosubstrate concentration) of the yeast-catalyzed bioreductions was performed using design of experiments (DOE), resulting in significant increases of conversion for most substrate–yeast strain combinations. Thus, several substrates could be fully or almost fully converted to the corresponding enantiopure (S)-alcohols with wild-type yeasts. Extending the scope of biocatalysts to recombinant ADHs [two (S)-selective ADHs from Candida parapsilosis (CpADH) and Rhodococcus aetherivorans (RaADH) and an (R)-selective one from Lactobacillus kefir (LkADH)] resulted in further improvements. Of the investigated biocatalysts, CpADH proved to be the most versatile, converting the more challenging shorter sidechain N-(2-oxopropyl)heterocycles as well. The (R)-selective Lactobacillus kefir ADH provided enantiopure (R)-alcohols, enabling the efficient enantiocomplementary synthesis of the target alcohols. The preparative-scale bioreductions under optimal conditions usually showed superior conversions compared to the screening reactions, resulting in enantiopure (S)- and (R)-enantiomers (ee > 99
Biofilms are traditionally viewed as surface-associated, extracellular polymeric substance (EPS)–encased aggregates. Here, we present a theoretical perspective positioning biofilm formation as a coordinated regulatory state transition, drawing on a synthesis of published transcriptomic, proteomic, and metabolic studies that document systemic reprogramming of gene regulatory networks, second-messenger signaling (e.g., cyclic di-GMP), quorum sensing circuits, and metabolic flux distribution. Spatial stratification within biofilms generates metabolically distinct subpopulations—including persisters and dormant cells—that enhance collective robustness. Using Salmonella enterica serovar Typhimurium as a model organism, we formalize quorum sensing inhibition (QSI) as one plausible bifurcation control parameter, with its destabilizing effects described by a coarse-grained phenomenological model governed by cooperativity, population density, and signal decay rates. We show, through bifurcation analysis and cross-referencing with published experimental biofilm disruption studies, that sufficiently strong signal-decay-type QSI can collapse the high-signal biofilm attractor without imposing strong bactericidal pressure. This network-centric perspective elucidates how destabilization of collective regulatory circuits—rather than direct cell killing—can enhance therapeutic susceptibility. Additionally, the framework provides a conceptual basis for combinatorial strategies integrating antivirulence interventions with conventional antimicrobials, with the potential to reduce the pace of resistance evolution by targeting cooperative rather than essential traits. Predictions arising from this framework require direct experimental validation to establish quantitative accuracy. • Biofilms can be conceptualized as coordinated regulatory attractor states sustained by multilayered feedback coupling. • QSI is formalized as one plausible bifurcation control parameter capable of destabilizing the high-commitment biofilm state when implemented as signal-degradation-type inhibition. • Network destabilization may enhance antimicrobial susceptibility while imposing lower evolutionary pressure than direct bactericidal approaches.
This proof-of-concept study evaluates plasma-modified polyethylene terephthalate (PET) filters for fungal bioaerosol collection and downstream culture and molecular analyses. Filters were plasma-coated using either 2-methyl-2-oxazoline (POX) or perfluorooctane (PFO), to enhance fungal spore adhesion and recovery using Aspergillus niger and Rhodotorula glutinis as representative of filamentous and yeast-like fungal species, respectively. Optimal capture was achieved at 15 L/min for 30 min, with saturation reached at 38 mg using biomass from four to five colony plates. Viability tests confirmed that spores collected on PFO and non-coated (NC) filters retained the ability to germinate, whereas POX coatings inhibited regrowth, indicating an antifungal surface effect. Molecular analyses demonstrated that 14–16 mg of captured biomass yielded sufficient DNA for downstream analyses. The internal transcribed spacer (ITS) region amplified using PCR produced clear amplicons ( 550 base pair (bp)) across all tested species. Sequencing provided accurate species identification with 99–100
The search for antibacterial agents remains a global priority, particularly against multidrug-resistant pathogens. In this study, microbial transformation of 1,8-dihydroxyanthraquinone (chrysazin) was performed to obtain derivatives with enhanced antibacterial activity. Biotransformation using Absidia corymbifera AUMC 7104 and Beauveria bassiana AUMC 5133 yielded two metabolites: 1,2,5,8-tetrahydroxyanthraquinone (1, quinalizarin) and 1,8-dihydroxy-3-methyl-anthraquinone (2, chrysophanol), respectively. Their structures were elucidated by HRESIMS, 1D/2D NMR analyses. To the best of our knowledge, this is the first report of quinalizarin production through microbial biotransformation. The antibacterial activities of both derivatives (1 and 2), along with their parent compound, were evaluated against multidrug-resistant Acinetobacter baumannii through in vitro assays. Compound 1 exhibited the least MIC values of 512–1024 µg/mL against A. baumannii isolates and was selected for further in vivo and in silico studies. In the murine infection model, the compound 1-treated group (group IV) exhibited a significant reduction (p < 0.05) in bacterial burden compared to the positive control group (group II). Immunohistochemical analysis of kidney, liver, and spleen tissues revealed modulation of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α, indicating anti-inflammatory properties alongside antibacterial activity. Molecular docking suggests a potential multi-target mechanism for compound 1, with favorable interactions with five critical bacterial proteins: MetRS, MurB, LptG/F, DXR, and MacB efflux transporter. These findings highlight quinalizarin as a potential lead compound for further antibacterial development. • Fungal biotransformation of chrysazin yielded the antibacterial agent quinalizarin. • Quinalizarin revealed in vitro and in vivo actions against Acinetobacter baumannii. • Docking studies suggested favorable interactions with multiple bacterial targets.
Strain-level identification is a key challenge in microbiology, particularly for monitoring microorganisms of interest such as probiotics. Traditional methods based on 16S rRNA gene sequencing often lack the resolution to discriminate closely related strains. This study investigates the potential of mobile genetic elements (MGEs), including transposons and prophages, as molecular markers for precise strain identification. Shewanella sp. Pdp11, a probiotic strain used in aquaculture, was selected as a model organism. Comparative in silico genome analyses revealed a unique transposon disrupting a phenazine biosynthesis gene, absent from other closely related Shewanella strains, which enabled the design of a highly specific PCR assay. This assay demonstrated a detection limit of 3 × 103 cells/mL with no amplification observed in fish intestinal microbiota DNA, indicating strong specificity even within complex bacterial communities. In addition, a complete prophage was characterized in the Pdp11 genome, containing bacterial genes potentially associated with stress tolerance functions; however, this prophage was not applied as a diagnostic marker in the current study due to its structural complexity. The proposed strategy requires prior genome sequence information to identify strain-specific MGEs before PCR marker development. Overall, the results highlight the feasibility of using transposons as genomic resources for developing high-resolution strain identification tools and lay the groundwork for future investigations into their stability and applicability in bacterial traceability systems. • PCR-based method developed to identify bacterial strains specifically. • Transposons identified as useful mobile elements for bacterial identification. • Prophages may serve as an alternative tool for bacterial fingerprinting, though additional gene-level studies are needed.
Short self-assembling peptides are versatile building blocks for enzyme-responsive nanostructured biomaterials. Here, we investigate how N-terminal acetylation affects the stability, fibrillogenesis, and protease-mediated fragment formation of two modular peptides, ug51 and ug52, composed of a fibrillogenic QAGIVV segment, an MMP-7-cleavable PLGL linker, and a C-terminal domain derived from motifs related to osteogenic growth peptides (OGPs). The stability of the peptides was assessed in water and cell culture medium, while secondary structure and nanoassembly were analyzed by circular dichroism, thioflavin T fluorescence, and transmission electron microscopy (TEM). Biological effects were evaluated in hFOB 1.19 osteoblasts. The non-acetylated peptide ug51 underwent spontaneous cleavage in the Val-Pro region, generating defined fragments, including PLGLYGFGG and, after prolonged incubation, the OGP-related LYGFGG sequence. In contrast, the N-terminally acetylated analog ug52 displayed markedly higher stability and formed ThT-positive, TEM-visible fibrillar assemblies. These assemblies remained susceptible to MMP-7-mediated processing, as shown by MALDI-TOF MS detection of the LYGFGG fragment after enzymatic incubation. Biological assays in hFOB 1.19 osteoblasts indicated overall cytocompatibility within the tested concentration range and peptide- and fragment-dependent effects on metabolic/proliferation-associated activity and migration-related responses. These findings suggest that N-terminal acetylation can shift the behavior of this modular peptide system from spontaneous degradation toward a more stable, fibril-forming, protease-processable state. Thus, this study provides proof-of-concept evidence that N-terminal acetylation can modulate the balance between peptide stability, supramolecular assembly, and enzymatic processability in a short modular peptide system. • N-terminal acetylation increases the apparent stability of the modular peptide ug52. • Non-acetylated ug51 undergoes spontaneous Val-Pro cleavage. • Acetylated ug52 forms ThT/TEM-positive fibrils that remain MMP-7-processable.
Abstract Selenium nanoparticles (SeNPs) have attracted significant attention owing to their unique physicochemical properties and promising biomedical applications. In the present study, a newly isolated halotolerant marine Bacillus sonorensis 2MNHR strain was employed for the extracellular biosynthesis of SeNPs. Bacterial isolates capable of reducing selenium oxyanions were obtained from seawater samples collected at Alexandria Harbor, Mediterranean Sea, Egypt. The ability of ten morphologically distinct bacterial isolates to reduce sodium selenite and sodium selenate under aerobic conditions was evaluated. Among them, only one isolate consistently reduced sodium selenite, as evidenced by the development of a characteristic red coloration in both liquid and solid media within 72 h, whereas no reduction was observed with sodium selenate. Extracellular reduction was confirmed using a cell-free supernatant assay. UV-Vis and FTIR analyses of the filtrate confirmed the involvement of biomolecules in selenite biotransformation, while GC–MS analysis revealed diverse organic compounds potentially responsible for reduction and stabilization. The biosynthesized SeNPs were comprehensively characterized using UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), zeta potential analysis, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX), and transmission electron microscopy (TEM). These analyses confirmed the formation of spherical, amorphous nanoparticles with sizes ranging from 80 to 200 nm (average ~ 160 nm) and a characteristic UV-Vis peak at 226 nm. A zeta potential of −38 mV indicated high colloidal stability. The SeNPs exhibited strong antimicrobial activity, with inhibition zones ranging from 23 to 32 mm and MIC values from 19.5 to 156.25 µg/mL. MBC/MIC ratios (≤ 2) confirmed bactericidal activity against most tested bacteria, while a ratio of 4 indicated borderline activity against Pseudomonas aeruginosa and fungistatic behavior against Candida albicans . These findings highlight the potential of halotolerant marine bacteria as sustainable platforms for the production of stable and biologically active SeNPs. Key points • Isolation of marine Bacillus sonorensis 2MNHR with high selenite-reducing potential • Efficient extracellular biosynthesis of stable selenium nanoparticles (SeNPs) • Integrated physicochemical characterization and antimicrobial evaluation of SeNPs
