Applied and Environmental Microbiology最新文献

{"title":"Development of a GFP-labeled <i>Pasteurella multocida</i> strain for <i>in vivo</i> organ infection tracing using a stable RCR-based genetic manipulation plasmid.","authors":"Chen Yuan, Wenqing Wang, Zhihui Wu, Haoshuai Song, Hongjie Fan, Zhe Ma","doi":"10.1128/aem.00787-26","DOIUrl":"10.1128/aem.00787-26","url":null,"abstract":"<p><p>Advances in microscopy have enabled the widespread application of <i>in vivo</i> pathogen tracking approaches to bacterial pathogenesis. <i>Pasteurella multocida</i> (<i>P. multocida</i>) is a major zoonotic pathogen causing severe respiratory diseases in livestock. However, genetic manipulation of clinical swine-derived isolates remains hindered by the lack of stable genetic tools. As a result, no genetically engineered <i>in vivo</i> tracking strain limits research in <i>P. multocida</i> infection dynamics. In this study, we evaluated diverse replication mechanisms and identified that rolling circle replication (RCR)-type replicons exhibit superior transformation robustness in swine isolates. Leveraging the temperature-sensitive pSET4s backbone and an optimized <i>mpheS</i> counter-selection marker, we developed a high-efficiency, markerless genetic manipulation system. The system exhibited high copy numbers and significantly enhanced transformation yields across diverse clinical swine isolates. To validate gene knockout efficiency, we performed markerless deletions of the capsule biosynthesis genes <i>hyaD</i> and <i>hyaE</i>. Phenotypic characterization revealed that hyaluronic acid (HA) deficiency led to complete attenuation of virulence in a murine model. Furthermore, we engineered a 15-Pm::GFP reporter strain via site-specific gene knock-in without detectable effects on bacterial growth or virulence. This strain enables direct visualization of bacterial colonization in the lung and liver by fluorescence imaging and allows real-time, <i>in situ</i> monitoring of pathogen and Kupffer cell interactions. Collectively, our results established an effective genetic toolkit for swine-derived <i>P. multocida</i> and developed fluorescently labeled strains for <i>in vivo</i> tracking. This plasmid provides a useful tool for investigating pathogenic mechanisms and <i>in vivo</i> infection dynamics of <i>P. multocida</i>.</p><p><strong>Importance: </strong><i>P. multocida</i> is a critical threat to global animal health, while the difficulty of genetic modification in swine isolates has interrupted the link of the genomic and pathogenic phenotypes. This study provides a highly efficient, RCR-based markerless manipulation system optimized with cross-serogroup applicability for swine isolates. Validated across 15 clinical swine isolates, this plasmid offers a robust tool for genetic analysis and the rational design of next-generation vaccines. By defining the essential roles of <i>hyaD</i> and <i>hyaE</i>, we demonstrate that the hyaluronic acid capsule is required for virulence and pulmonary colonization. Moreover, the development of a biologically fluorescent reporter strain enables high-resolution, <i>in situ</i> tracking of infection dynamics, providing a powerful tool for real-time visualization during <i>P. multocida</i> infection.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0078726"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599540/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148711198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The truncated major pilin subunit SBP2' contributes to <i>Streptococcus suis</i> meningitis by interacting with host plasminogen.","authors":"Genglin Guo, Pei Li, Yu Zhou, Quan Li, Yanfei Yu, Jiahui An, Wei Zhang","doi":"10.1128/aem.01267-26","DOIUrl":"10.1128/aem.01267-26","url":null,"abstract":"<p><p>Meningitis is one of the most striking manifestations of <i>Streptococcus suis</i> infection. Although multiple virulence-associated factors have been identified, the mechanisms underlying meningitis development remain incompletely understood. In <i>S. suis</i>, a <i>srtBCD</i> pilus gene cluster has been identified; our previous study suggested its association with bacterial virulence. In this study, we investigated the role of the <i>srtBCD</i> cluster in <i>S. suis</i> pathogenesis and confirmed that SBP2' was specifically localized on the bacterial surface and was found to be essential for full virulence in a murine infection model, whereas deletion of other minor subunits had minimal impact. Using brain microvascular endothelial cells (BMECs), microglia, and a BALB/c mouse model, we examined how SBP2' promotes the development of <i>S. suis</i> meningitis. Our results show that SBP2' enhances bacterial colonization of BMECs and recruits host plasminogen, facilitating extracellular matrix (ECM) degradation, and thereby promoting bacterial invasion. In addition, SBP2' enables <i>S. suis</i> to evade microglial phagocytosis and improves its intracellular survival. Importantly, a monoclonal antibody targeting SBP2' conferred significant immunoprotection in mice. Together, these findings identify SBP2' as an important virulence factor and plasminogen-binding receptor that facilitates <i>S. suis</i> traversal of the blood-brain barrier.IMPORTANCE<i>Streptococcus suis</i> is an important zoonotic bacterial pathogen that could lead to severe damage in the central nervous system, but the mechanism underlying the breakthrough of the blood-brain barrier is still unclear. Pili are commonly considered virulence factors and subunit vaccine candidates, but no pilus structure could be observed on the surface of <i>S. suis</i> serotype 2. In this study, we found that the <i>srtBCD</i> pilus cluster, which was considered a pseudogene because of the truncation of the major pilus subunit, could be expressed, and the truncated major pilus subunit could be detected on the cell surface and be involved in the pathogenesis of <i>S. suis</i> serotype 2. Notably, monoclonal antibodies targeting SBP2' provide immunoprotection in mice, reducing bacterial loads and brain damage. These findings identify SBP2' as a key virulence factor and therapeutic target, offering insights into <i>S. suis</i> meningitis mechanisms.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0126726"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599487/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148700544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Gti1/Pac2 family protein CFG1 controls fungal chlamydospore formation through orchestrating cell wall remodeling, lipid metabolism, and ribosome biogenesis.","authors":"Yiting Hou, Yifan Li, Cheng Chen, Xichen Ling, Minglei Cheng, Jianwei Pu, Tingting Sun, Jian Zhang, Qirong Shen, Zhenzhong Yu","doi":"10.1128/aem.00867-26","DOIUrl":"10.1128/aem.00867-26","url":null,"abstract":"<p><p>The morphological transition of fungi from vegetative hyphae to thick-walled chlamydospores enhances their longevity in harsh environmental conditions. Owing to this resilience, pathogenic fungi that form chlamydospores are particularly difficult to control. Therefore, understanding the mechanisms of chlamydospore formation is critically important. Here, we show that the hyphae of the filamentous fungus <i>Trichoderma guizhouense</i> can differentiate into typical terminal and intercalary chlamydospores characterized by double-layered spherical or ellipsoidal cell walls with accumulated lipid bodies and nuclei. We found that during chlamydospore formation, ribosome biogenesis was gradually downregulated, indicating the entry of cells into dormancy. Comparative transcriptomic analyses across developmental stages and media identified the Gti1/Pac2 family protein CFG1 as an essential regulator, as the Δ<i>cfg1</i> strain failed to form chlamydospores under all inducing conditions. Lipidomic analysis showed its involvement in lipid metabolism, and mutants lacking lipid metabolism genes <i>pdat</i> or <i>dgat</i> produced fewer chlamydospores. Our work reveals the molecular mechanism of chlamydospore formation in <i>T. guizhouense</i>.IMPORTANCEIn fungal biology, the morphological transition from vegetative hyphae to thick-walled, lipid-rich chlamydospores represents a fundamental developmental switch into dormancy, crucial for survival under environmental stress. Understanding the regulatory mechanisms behind this process is essential for deciphering the basic principles of fungal cell differentiation and adaptation. This study employs multi-omics approaches to systematically characterize chlamydospore formation and identifies the Gti1/Pac2 family protein CFG1 as a master regulator. Functional analysis reveals that CFG1 governs this transition by directly influencing lipid metabolism-a key pathway for spore maturation and structural integrity. These findings uncover a previously unknown molecular switch in fungal development and provide new insights into how filamentous fungi coordinate metabolic reprogramming with cellular differentiation to ensure long-term survival.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0086726"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599505/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148672971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"OxyR regulates the oxidative stress response in <i>Zymomonas mobilis</i> during oxic growth and anoxic biofuel fermentation.","authors":"Emma C Boismier, Magdalena M Felczak, Kevin S Myers, Michaela A TerAvest","doi":"10.1128/aem.01044-26","DOIUrl":"10.1128/aem.01044-26","url":null,"abstract":"<p><p>The bacterium <i>Zymomonas mobilis</i> is widely studied for its potential as an industrial biofuel producer. Anoxic fermentation by <i>Z. mobilis</i> in lignocellulosic hydrolysate can generate bioethanol from renewable plant biomass. In this study, we deleted a gene from the <i>Z. mobilis</i> genome encoding a homolog of OxyR, a transcription factor that activates an oxidative stress response in bacteria to reduce reactive oxygen species (ROS). Deletion of this transcription factor inhibited growth of <i>Z. mobilis</i> in oxic, but not anoxic, conditions in laboratory media. A ROS probe revealed that the <i>oxyR</i> response is required to reduce intracellular ROS during oxic growth. Importantly for biofuel production, the absence of <i>oxyR</i> inhibited growth and delayed ethanol production during anoxic hydrolysate fermentation. To determine the source of oxidative stress in hydrolysates, we grew Δ<i>oxyR</i> in a synthetic hydrolysate containing known inhibitors found in hydrolysates. There was no growth defect in Δ<i>oxyR</i> in the synthetic hydrolysate, indicating that known inhibitory compounds are not the source of anoxic oxidative stress. We determined that ammonia-fiber expansion switchgrass hydrolysate contains significant peroxide concentrations. Addition of catalase to hydrolysate improves growth of both Δ<i>oxyR</i> and wild-type <i>Z. mobilis</i> in hydrolysate. This study uncovers an important source of stress to <i>Z. mobilis</i> during biofuel fermentation.IMPORTANCEFermentation of non-food biomass is a promising avenue for sustainable production of fuels and chemicals, but several challenges currently limit the applicability of this technology. One major hurdle is that when biomass is deconstructed into a fermentable form, many byproducts are generated that inhibit microbial fermentation. Here, we investigated how a fermentative bacterium, <i>Zymomonas mobilis</i>, experiences oxidative stress during anoxic biomass fermentation and identified genes important in this response. These findings provide a better understanding of the stresses faced by <i>Z. mobilis</i> during biofuel production. Fully understanding the effects of hydrolysates on biofuel-producing microbes is crucial for optimizing production and making carbon-neutral fuel a reality.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0104426"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599515/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148668235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Industrial effluent-derived <i>Acinetobacter</i> sp. PbS1A2 as a bioremediator against lead toxicity in <i>Labeo rohita</i>.","authors":"Saima Zafar, Asma Ashraf, Sehrish Fatima, Farkhanda Asad, Kafeel Ahmad, Yusuf Tutar, Mudassir Hassan","doi":"10.1128/aem.00527-26","DOIUrl":"10.1128/aem.00527-26","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Lead pollution is recognized as a major global environmental problem that poses a serious threat to ecological integrity and environmental sustainability. The current study shows the bioremedial potential of Pb-resistant &lt;i&gt;Acinetobacter&lt;/i&gt; sp. PbS1A2 in &lt;i&gt;Labeo rohita&lt;/i&gt;. The fish were divided into three experimental treatments, namely, Control (T&lt;sub&gt;0&lt;/sub&gt;), Pb only (T&lt;sub&gt;1&lt;/sub&gt;), and Pb + &lt;i&gt;Acinetobacter&lt;/i&gt; sp. (T&lt;sub&gt;2&lt;/sub&gt;). The treatment T&lt;sub&gt;2&lt;/sub&gt; was particularly exposed to a concentration of 1.5 × 10&lt;sup&gt;8&lt;/sup&gt; CFU/mL of &lt;i&gt;Acinetobacter&lt;/i&gt; sp. along with Pb (1 mg L&lt;sup&gt;-1&lt;/sup&gt;) for a period of 30 days. The results revealed that &lt;i&gt;Acinetobacter&lt;/i&gt; sp. PbS1A2 could tolerate Pb concentrations up to 30 mM, along with resistance to other heavy metal ions. Pb exposure significantly increased the activity of all antioxidant enzymes, with glutathione transferase exhibiting the greatest increase (795%), followed by peroxidase (229%), superoxide dismutase (195%), catalase (104%), and ascorbate peroxidase (28%). Furthermore, Fourier transform infrared spectroscopy was employed to identify the functional groups involved in Pb biosorption, while intracellular accumulation was confirmed via energy dispersive X-ray and scanning electron microscopy analyses. At the end of the 1-month trial, fish in the T&lt;sub&gt;2&lt;/sub&gt; group treated with &lt;i&gt;Acinetobacter&lt;/i&gt; sp. exhibited a significantly higher survival rate, improved growth performance, better body composition, and increased amylase and protease activities than those in the T&lt;sub&gt;1&lt;/sub&gt; group. Furthermore, the T&lt;sub&gt;2&lt;/sub&gt; treatment mitigated the negative impacts of Pb on hematological and biochemical parameters and restored histological damage in the fish organs. The current study suggests that &lt;i&gt;Acinetobacter&lt;/i&gt; sp., due to its heavy metal tolerance, could effectively ameliorate Pb bioavailability in aquatic habitats and enhance environmental health.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Importance: &lt;/strong&gt;The continuously rising Pb discharge in aquatic ecosystems, particularly in the industrial regions of South Asia, jeopardizes ecological integrity and the health of economically crucial fish such as &lt;i&gt;Labeo rohita&lt;/i&gt;, consequently affecting food security. Conventional remediation techniques are often expensive, energy-intensive, and pose ecological risks. This study addresses a significant gap by presenting a thorough bioremediation process encompassing the isolation and characterization of a newly identified multi-metal-resistant &lt;i&gt;Acinetobacter&lt;/i&gt; sp. (PbS1A2) from industrial wastewater, which facilitates &lt;i&gt;in vivo&lt;/i&gt; recovery in &lt;i&gt;Labeo rohita&lt;/i&gt; contaminated with Pb. Isolated from a contaminated site, &lt;i&gt;Acinetobacter&lt;/i&gt; sp. have evolved natural metal-resistant mechanisms under environmental stress, resulting in better remediation than lab-engineered options. This is distinguished from studies that solely address the &lt;i&gt;in vitro&lt;/i&gt; efficiencies of Pb removal. The research offers e","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0052726"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599521/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148787616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The urinary tract commensal <i>Peptoniphilus</i> spp. encodes a novel 17β-hydroxysteroid dehydrogenase.","authors":"Briawna Binion, Saeed Ahmad, Taojun Wang, Elizabeth Tang, Betsy Barnick, Damie Olukoya, Pauline Mbuvi, Debapriya Dutta, John W Erdman, H Rex Gaskins, Glen Yang, Joseph Irudayaraj, Jason M Ridlon","doi":"10.1128/aem.00623-26","DOIUrl":"10.1128/aem.00623-26","url":null,"abstract":"<p><p>Microbial steroid metabolism represents an underappreciated extension of the vertebrate endocrine system, with growing evidence that host-associated microbes contribute to the diversity and bioavailability of sex steroids to human tissues. Emerging studies have linked microbial androgen metabolism to urinary microbiome composition and to resistance to androgen deprivation therapy (ADT) in prostate cancer. While microbial pathways capable of converting steroid precursors such as cortisol to androgens, via the steroid-17,20-desmolase pathway, such as DesG-mediated interconversion of androstenedione to testosterone, have been reported, the diversity of enzymes mediating downstream androgen interconversion remains incompletely defined. Here, we investigate the androgen-forming capabilities of anaerobic bacteria from the male genitourinary microbiome, focusing on NADPH-dependent 17β-hydroxysteroid dehydrogenases (17β-HSDHs) that catalyze the interconversion of androstenedione and testosterone. We isolated androgen-forming bacterial strains from human male urine and identified a previously uncharacterized 17β-HSDH in <i>Peptoniphilus obesi</i>, demonstrating that this enzyme catalyzes the NADPH-dependent reduction of androstenedione to testosterone and the reverse oxidation reaction. Sequence similarity searches further identified a similar 17β-HSDH in <i>Anaerococcus</i>, which was synthesized and functionally validated, revealing conserved activity despite low sequence identity to the previously characterized urinary tract enzyme DesG from <i>Propionimicrobium lymphophilum</i>. The enzymes were found to have broad substrate specificity for C₁₉ and C₁₈ 17-keto- and 17β-hydroxysteroids. Together, these findings expand the known diversity of microbial 17β-HSDHs and identify previously unrecognized androgen-forming activities within the genitourinary microbiome.IMPORTANCEMicrobial steroid-transforming pathways may provide a mechanism by which commensal anaerobes contribute to androgen availability in the genitourinary tract. By identifying novel 17β-hydroxysteroid dehydrogenases from <i>Peptoniphilus</i> and <i>Anaerococcus</i>, genera repeatedly associated with prostate cancer, this study provides mechanistic insight into how microbial steroid metabolism may influence hormone-driven disease.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0062326"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599511/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148824319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Top-down/bottom-up consortia achieve robust γ-HCH degradation and reduced methanogenic contribution in wetlands.","authors":"Meng Liu, Xin Su, Xiaowei Huang, Xueling Yang, Yuxuan Chen, Jianming Xu, Yan He","doi":"10.1128/aem.01133-26","DOIUrl":"10.1128/aem.01133-26","url":null,"abstract":"<p><p>Generalist non-obligate organochlorine-degrading bacteria (ODB) play an important role in the bioremediation of γ-hexachlorocyclohexane (γ-HCH), yet their ecological roles and functional mechanisms remain underexplored. In this study, we used both \"top-down\" and \"bottom-up\" strategies to construct two functional consortia (M and Y13) based on non-obligate ODB. Both consortia demonstrated efficient degradation in sediment microcosms, reducing γ-HCH (C/C₀) to 63.0% (M) and 56.1% (Y13). Simultaneously, functional microbial consortia inoculation significantly suppressed the CO₂ reduction methanogenesis pathway compared with the non-inoculated group (<i>P</i> < 0.05), as evidenced by a marked decline in the CH₄/CO₂ ratio in inoculated groups. The well-known degradation gene <i>pceA</i> was enriched in the Y13 group, and the co-localization of <i>pceA</i>-encoding contigs with mobile genetic elements was identified. Notably, <i>Enterococcus</i> was found to have successfully colonized inoculated groups. It has strong environmental evolutionary adaptability and might acquire organochlorine-degrading genes through horizontal gene transfer under pollution stress. The broad applicability of non-obligate ODB (e.g., <i>Enterococcus</i>) makes them a promising candidate for future environmental remediation efforts, breeding new avenues of \"One Health\" win-win solutions in carbon reduction during pollution remediation for wetlands.</p><p><strong>Importance: </strong>γ‑Hexachlorocyclohexane (γ‑HCH) is a representative organochlorine pesticide and a well‑known persistent organic pollutant that poses significant risks to ecosystems and human health. Microbial anaerobic degradation is a key process in the natural attenuation and engineered cleanup of γ‑HCH contamination. The effective application of obligate organohalide-respiring bacteria often requires precise management. In parallel, newly discovered non‑obligate organohalide-respiring bacteria capable of degrading γ‑HCH have emerged as promising alternatives, yet their performance and ecological interactions in realistic sediment systems remain poorly understood. This study examines the degradation mechanisms and microbial ecology of non-obligate organohalide-respiring bacterial functional consortia in complex media. The findings provide critical insights for developing effective bioaugmentation strategies for lindane‑contaminated coastal wetlands and may offer a useful framework for managing other recalcitrant halogenated pollutants in similar environments.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0113326"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599539/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148838939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diversification of biofilm architecture among freshwater <i>Pararheinheimera</i> isolates.","authors":"Amanda E Appel, Alexandra G Goetsch, Ellen W van Wijngaarden, Daniel J Novacek, Peter M Burnham, Meredith N Silberstein, David M Hershey","doi":"10.1128/aem.00400-26","DOIUrl":"10.1128/aem.00400-26","url":null,"abstract":"<p><p>Extracellular matrices that scaffold microbial biofilms offer a rich source of polymeric materials with a range of potential applications. However, our understanding of these matrices is largely restricted to model organisms that form biofilms with specific architectures. Examining biofilms from understudied niches has the potential to identify extracellular matrices with novel properties. Here, we targeted a resource-rich boundary at the top of the water column known as the air-liquid interface (ALI). ALIs lack a solid substrate for cellular attachment, suggesting that microbes utilize specialized biofilm architectures to persist at this boundary. We used samples from a lake to enrich for microbes that colonize the ALI. Mixed-species pellicle biofilms formed rapidly in these enrichments and displayed a pronounced ecological succession. We isolated 31 members of the genus <i>Pararheinheimera</i> from early stages of pellicle maturation that formed five phylogenetically distinct clades. We used representative isolates to show that only one <i>Pararheinheimera</i> clade formed adherent films resembling classical pellicles. Isolates from the remaining clades formed floating structures that could be categorized either as non-adhesive films or viscous masses (VMs). VM pellicle formation was a polyphyletic trait that correlated with a mucoid appearance on agar plates, suggesting that the process is driven by copious extracellular matrix secretion. Matrices from VM biofilms were largely non-adhesive, contained a mixture of acidic polysaccharides and proteins, and formed thermally stable, shear-thinning hydrogels. Our results demonstrate that ALI colonization strategies vary widely even among closely related aquatic bacteria and identify VM pellicles as a promising platform for biomaterials development.</p><p><strong>Importance: </strong>Microbial biofilms contain specialized polymers with immense industrial potential, yet only a subset of biofilm architectures has been studied in detail. Many aquatic microbes live within a boundary at the surface of lakes, rivers, and oceans known as the air-liquid interface (ALI). The strategies microbes use to form biofilms at this boundary remain poorly characterized. Our study investigated how bacteria from a freshwater lake accumulate at the ALI. Lake water samples incubated in nutrient medium formed a floating pellicle biofilm, and we isolated 31 bacteria from the genus <i>Pararheinheimera</i> that were abundant during the early stages of pellicle formation. Only a subset of <i>Pararheinheimera</i> isolates formed traditional pellicle biofilms. Most formed either thin, non-adhesive films or large, gelatinous aggregates that appeared to persist at the ALI due to buoyancy. These findings expand our understanding of biofilm diversity in aquatic systems and suggest that the production of buoyant hydrogels could be useful scaffolds for engineering new materials.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0040026"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599514/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148838693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A capsid hinge region in European hepatitis E virus links mutations to genotype, virion surface properties, and environmental circulation.","authors":"Samy Kasmi, Guillaume Sautrey, Cédric Hartard, Fabienne Quilès, Jean-Luc Bailly, Alexis de Rougemont, Hélène Jeulin, Raphael E Duval, Christophe Gantzer, Evelyne Schvoerer","doi":"10.1128/aem.01445-26","DOIUrl":"10.1128/aem.01445-26","url":null,"abstract":"<p><p>Hepatitis E virus (HEV) exhibits genetic diversity associated with distinct public health outcomes and circulation patterns across interconnected human and environmental reservoirs. Most studies have focused on genome-wide diversity, revealing relationships between genotype, virulence, and dissemination routes. However, the role of localized mutations in the capsid protein (ORF2), which may influence the extracellular fate and ecology of HEV through changes in surface biological and physicochemical properties of virions, received limited attention. Here, we combined large-scale analysis of European HEV sequences, structural modeling, and physicochemical characterization to investigate such variations in ORF2. Analysis of ORF2 sequences on a genomic segment highly reported in GenBank, derived from patients and the environment, revealed recurrent mutation motifs (single H354Y and triple H354Y-G357S-V364I motifs) located in a conserved capsid hinge region connecting the middle (M) and protruding (P) domains of the protein. These motifs displayed distinct frequency patterns according to sequence sources and were associated with genotypes 3 and 1, respectively. AlphaFold-based modeling identified this region as a flexible interface between the M and P domains and indicated that mutations reduce predicted alignment error of the P domain relative to the overall protein model, consistent with altered exposure at the virion surface. <i>In vitro</i> analyses of synthetic peptides encompassing this critical region revealed increased hydrophobicity and structural rearrangements, supporting local modulation of capsid surface properties. Together, these results identify a structurally and physicochemically sensitive hinge region in the HEV capsid, suggesting a link between ORF2 sequence variations, genotype, virion surface properties, and environmental circulation.IMPORTANCEHepatitis E virus (HEV) is a major cause of viral hepatitis worldwide, which is transmitted through complex, genotype-linked dissemination routes between humans, animals, and environmental waters. Understanding the circulation dynamics of HEV virions is essential for improving environmental surveillance, risk assessment, and public health strategies within a One Health approach. By combining genetic, structural, and physicochemical analyses, this study highlights specific mutation motifs in a hinge region of the ORF2 capsid protein likely to link distinct distribution patterns of HEV across environmental reservoirs to potential changes in virion surface properties. Such mutation motifs may serve as molecular signatures for exploring virus persistence and dissemination in environmental contexts. Overall, this work provides a new framework for connecting viral genetic variation to environmental behavior beyond traditional genotype classification.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0144526"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599484/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148838716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spore-forming <i>Clostridia</i> as overlooked determinants of microbial risk in wastewater reuse systems.","authors":"Daniel N Miller, Lisa M Durso","doi":"10.1128/aem.01000-26","DOIUrl":"10.1128/aem.01000-26","url":null,"abstract":"<p><p>Using treated municipal wastewater for crop irrigation is a key strategy to combat drought-induced water scarcity. However, current wastewater reclamation standards systematically underestimate risks from spore-forming pathogens. As highlighted in a recent minireview by A. Mrozinski, C. Le Maréchal, and E. Topp in <i>Applied and Environmental Microbiology</i> (92:e00173-26, 2026, https://doi.org/10.1128/aem.00173-26), <i>Clostridioides difficil</i>e and <i>Clostridium perfringens</i> survive conventional disinfection, persist indefinitely in agricultural soils, and harbor critical antibiotic resistance genes. To safeguard the food supply and protect public health, regulatory frameworks must shift from relying solely on standard vegetative bacterial indicators and include monitoring resilient, spore-forming pathogens.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0100026"},"PeriodicalIF":4.2,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13599517/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148862798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}