mSphere最新文献

{"title":"Expanded prevalence of group 4 capsule expression and its genetic requirements in a broad array of <i>Shigella</i> strains.","authors":"Brock W Brethour, Tao Wu, Bing Guo, Megan D Broussard, David A Rasko, Eileen M Barry","doi":"10.1128/msphere.00354-26","DOIUrl":"10.1128/msphere.00354-26","url":null,"abstract":"<p><p>The expression of a group 4 capsule (G4C) has been identified in <i>Shigella sonnei</i> and <i>Shigella flexneri</i> serotype 6 and demonstrated to play a significant role in pathogenic processes in <i>S. sonnei</i>. However, it has not been examined phenotypically in <i>S. flexneri</i> 6. Despite the impact of G4C, no systematic analysis of its expression or the presence of the genomic determinants has been performed across a large collection of <i>S. sonnei</i> and <i>S. flexneri</i> serotypes 2a and 6 or any of the other >46 <i>Shigella</i> strains and serotypes that cause disease. Our examination of the genomes of 1,219 geographically diverse <i>Shigella</i> isolates revealed the presence of intact <i>gfc</i> operons not only in the majority (≥98%) of <i>S. sonnei</i> and <i>S. flexneri</i> 6 strains but also, surprisingly, in the majority (≥97%) of <i>Shigella boydii</i> and <i>Shigella dysenteriae</i> strains. Approximately 95% of non-serotype 6 <i>S. flexneri</i> isolates contained a range of diverse <i>gfc</i> mutations preventing G4C expression; the remaining 5% contained an intact <i>gfc</i> operon yet had single-nucleotide polymorphisms within the promoter that resulted in lack of expression. These findings establish that no <i>S. flexneri</i> serotypes other than 6 express a G4C. Capsule expression was directly linked to reduced epithelial cell invasion for all strains examined, confirming differences in pathogenic processes between capsule-positive and capsule-negative <i>Shigella</i> strains. This work identifies a more widespread expression of capsule among <i>Shigella</i> strains than previously appreciated and identifies critical genetic requirements.</p><p><strong>Importance: </strong><i>Shigella</i> is the leading cause of moderate-to-severe diarrhea in 1- to 5-year-old children in low-resource settings, yet there is no licensed vaccine. Despite the impact of the group 4 capsule (G4C) on <i>Shigella</i> epithelial cell invasion, its expression has not been determined for the majority of <i>Shigella</i> species and serotypes that cause disease. This study investigated the presence of intact genes necessary for G4C expression in 1,219 geographically diverse <i>Shigella</i> isolates and examined phenotypes associated with G4C expression. We report that G4C is much more widespread than previously appreciated; it is expressed in the vast majority of <i>Shigella sonnei</i> and <i>Shigella flexneri</i> 6 clinical isolates, as well as <i>Shigella boydii</i> and <i>Shigella dysenteriae</i> strains. No <i>S. flexneri</i> serotypes outside of serotype 6 expressed a G4C. This study provides evidence that G4C expression in <i>Shigella</i> is much more widespread than previously recognized and emphasizes the importance of capsule expression in host-pathogen interactions.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0035426"},"PeriodicalIF":4.0,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621845/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148713346","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":"<i>Fmr1</i> mutation is associated with gut microbiome structure and diversity as well as intestinal barrier integrity and function in a sex- and genotype-dependent manner.","authors":"Sabiha Alam, Ciaran A Shaughnessy, Edralin A Lucas, Femi Olawale, Babu Z Fathepure, Elizabeth A McCullagh","doi":"10.1128/msphere.00442-26","DOIUrl":"10.1128/msphere.00442-26","url":null,"abstract":"<p><p>Fragile X syndrome (FXS) is the leading monogenic cause of autism spectrum disorder (ASD), caused by mutation in the <i>Fmr1</i> gene. In addition to cognitive and behavioral challenges, FXS patients often experience altered gut microbiome-induced gastrointestinal (GI) problems. Evidence suggests that an altered gut microbiome can disrupt mucosal barrier and promote inflammation, leading to impaired intestinal barrier integrity and function. However, the mechanisms by which the gut microbiome alters the barrier integrity and contributes to GI pathology in FXS remain poorly understood. To address this gap, we tested the hypothesis that <i>Fmr1</i> mutation is associated with gut microbiome composition, altering transcriptional markers of intestinal barrier regulation, and gut barrier physiology in mice. To test our hypothesis, we used an <i>Fmr1</i> knockout (KO) mouse model with wild-type (WT) littermates as controls. First, we performed 16S ribosomal RNA sequencing to characterize gut microbial community structure and diversity across genotypes and sexes. Among the alpha-diversity metrics, only Chao1 showed significant differences across female genotypes in both fecal and cecal contents. Additionally, qRT-PCR analysis of ileal samples revealed reduced barrier and mucosal defense gene expression in female KO and Het mice compared with WT females. Next, we used an Ussing chamber assay to test gut epithelial permeability and function. Our physiological data showed that female Het mice had increased transepithelial resistance compared to WT females, indicating a tighter epithelial barrier. Overall, FXS is associated with modest genotype- and sex-specific microbiome variation, impaired gut barrier integrity, and altered epithelial barrier function in female mice.IMPORTANCEFragile X syndrome (FXS), the most common inherited cause of autism, affects not only brain function but also physical health, including chronic gastrointestinal (GI) problems that are often overlooked. This study reveals that a single genetic mutation linked to FXS is associated with the gut microbiome and the intestinal barrier-the body's frontline defense against inflammation and disease-in a sex-specific manner. Using a mouse model, we show that females carrying the <i>Fmr1</i> mutation exhibit changes in gut microbes, reduced expression of genes that protect the intestinal lining, and altered gut barrier function. These findings highlight a critical gut-genetic connection in FXS and point to the intestine as an important, yet underappreciated, site of disease impact. By linking genetic risk for neurodevelopmental disorders to gut health, this work opens new avenues for understanding-and potentially treating-the gastrointestinal symptoms experienced by individuals with FXS.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0044226"},"PeriodicalIF":4.0,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621844/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148830820","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":"Evaluating an anti-idiotype derived germline-targeting immunogen designed to elicit VRC01-class precursors in human antibody transgenic mice.","authors":"Crystal B Chhan, Yu-Hsin Wan, Andrew Wilcox-King, Leah J Homad, Nicholas T Aldridge, Roman Iureniev, Leonidas Stamatatos, Andrew T McGuire","doi":"10.1128/msphere.00317-26","DOIUrl":"10.1128/msphere.00317-26","url":null,"abstract":"<p><p>An effective HIV-1 vaccine will likely need to elicit broadly neutralizing antibodies (bNAbs) that bind relatively conserved regions of the otherwise highly variable envelope glycoprotein. Among these, VRC01-class bNAbs are a reproducible antibody class that bind the CD4-binding site through genetic features encoded by the VH1-2 heavy chain and a light chain containing a rare five-amino-acid-long complementarity-determining region 3 (CDRL3). We previously developed a germline-targeting immunogen, iv4/iv9, derived from anti-idiotypic monoclonal antibodies (ai-mAbs) that target these genetic signatures of VRC01-class bNAbs. Here, we applied structure-guided modification of iv4/iv9 that improved selective binding to VRC01 precursors <i>in vitro</i> and carried out immunizations in ATX-GK mice. These mice are transgenic for human antibody genes, producing a diverse, genetically human antibody repertoire. We found that ATX-GK mice harbor VRC01 precursors at frequencies lower than those found in humans. Class-switched VRC01 precursors were detected in a minority of mice immunized with a modified iv4/iv9 immunogen. Collectively, these results indicate that the ATX-GK mice have utility to evaluate VRC01-class germline-targeting immunogens but are a stringent model due to a low frequency of VRC01-class B cells. They further suggest that the ai-mAb immunogens evaluated herein will require further optimization to reproducibly prime VRC01-class B cells in ATX-GK mice.IMPORTANCEAn effective HIV-1 vaccine will likely need to elicit broadly neutralizing antibodies (bNAbs) that bind relatively conserved regions of the otherwise highly variable envelope glycoprotein. Among these, VRC01-class bNAbs are a reproducible antibody class that bind the CD4-binding site through genetic features encoded by the VH1-2 heavy chain and a light chain containing a rare five-amino-acid-long complementarity-determining region 3 (CDRL3). We previously developed a germline-targeting immunogen, iv4/iv9, derived from anti-idiotypic monoclonal antibodies that target these genetic signatures of VRC01-class bNAbs. Here, we evaluate the B-cell response to immunization with iv4/iv9 and with a structure-guided modified iv4/iv9 in ATX-GK mice. These modifications are intended to improve the selectivity of VRC01 precursors in a diverse polyclonal B cell repertoire. These mice are transgenic for human antibody genes, producing a diverse, genetically human antibody repertoire. We found that ATX-GK mice harbor VRC01 precursors at frequencies lower than those found in humans. Class-switched VRC01 precursors were detected in a minority of animals immunized with the modified iv4/iv9. Collectively, these results indicate that although the iv4/iv9 immunogen did not reproducibly elicit VRC01-class B cells, ATX-GK mice have utility to evaluate VRC01-class germline-targeting immunogens but are a stringent model due to a low frequency of VRC01-class B cells.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0031726"},"PeriodicalIF":4.0,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621863/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148866100","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 distribution of acidophilic iron oxidizers is consistent with environmental filtering, dispersal limitation, and competition.","authors":"Christen L Grettenberger, Caden Williams, Trinity L Hamilton","doi":"10.1128/msphere.00351-26","DOIUrl":"10.1128/msphere.00351-26","url":null,"abstract":"<p><p>Acid mine drainage (AMD) is a global pollution problem characterized by low pH and high concentrations of metals. Active remediation is often cost-prohibitive, but Fe(II)-oxidizing microbes may be used for passive bioremediation. To leverage these species, we must understand the factors that control their distribution. Here, we examined the environmental and ecological factors that control these species with the aim of determining if microbial seeding is a viable remediation strategy. Although stochastic processes appeared to control the distribution of the majority of taxa inhabiting AMD ecosystems, the distribution of Fe(II) oxidizers appeared to be driven by environmental filtering and competition. The abundance of all the major Fe(II)-oxidizing genera had significant relationships with pH, with pH explaining 10%-38% of the variation in their abundance. The genera appeared to have pH preferences, with <i>Acidithiobacillus</i> and <i>Leptospirillum</i> preferring environments with pH below 3, <i>Gallionella, Sideroxydans,</i> and <i>Ferritrophicum</i> preferring environments with pH above 3.5, and <i>Ferrovum</i> preferring intermediate-pH environments. Once the effect of pH is removed, genera that share pH preferences were negatively correlated, indicating that they were likely competing for the Fe(II)-oxidizing niche in their preferred environments. Communities were also shaped by dispersal limitation, which suggests that microbial seeding may be possible in these environments. Future seeding attempts should consider species interactions and ecology more generally to inform their efforts.</p><p><strong>Importance: </strong>Acid mine drainage (AMD) is a global pollution problem affecting streams worldwide. One method of remediating AMD is by using naturally occurring microbial communities to remove iron and other metals. However, we do not have a complete understanding of the factors that control the distribution of these species or if it is possible to seed species from one environment into another. Here, we examine the factors that control community assembly in AMD ecosystems. We find that individual species appear to be dispersal-limited; thus, microbial seeding may be a viable method for AMD remediation.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0035126"},"PeriodicalIF":4.0,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621859/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148866229","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":"Expansion and optimization of the auxin-inducible degron 2 (AID2) system in <i>Candida</i> pathogens.","authors":"Emily L Danzeisen, Michelle V Lihon, Kedric L Milholland, Taylor R Bias, Audrey F Bates, Mark C Hall","doi":"10.1128/msphere.00359-26","DOIUrl":"10.1128/msphere.00359-26","url":null,"abstract":"<p><p>The auxin-inducible degron (AID) technology is a convenient and powerful tool for protein functional characterization in a broad array of eukaryotic species. We recently demonstrated that the original AID and improved AID2 systems are very effective at rapid protein depletion in <i>Candida albicans,</i> and described a limited set of reagents for their use in certain auxotrophic lab strains. With an eye toward broader applicability with improved flexibility, we report here a new series of template vectors suitable for employing AID2 technology in prototrophic <i>C. albicans</i> strains, such as clinical isolates and the reference strain SC5314. We adapted a common recyclable antibiotic marker system for the required genome editing steps, and developed a strategy for simultaneous CRISPR/Cas9-mediated tagging of both target alleles. We also developed a composite all-in-one tagging cassette that combines the degron tag and the <i>OsTIR1^F74A</i> gene for single-step strain engineering. We added a fluorescent protein tag option and designed and validated an approach for N-terminal tagging that retains natural promoter control. We also compared the effectiveness of the two commonly used synthetic auxins, 5-phenyl-indole-3-acetic acid and 5-adamantyl-indole-3-acetic acid, and the two common <i>OsTIR1</i> variants, F74A and F74G, and provide guidelines for using the new AID2 system. Finally, using the novel all-in-one cassette, we demonstrate that the AID2 system also works in <i>Candida auris</i>, albeit less effectively under some conditions. The new reagents should enhance the convenience and accessibility of the AID2 system for the <i>Candida</i> research community.</p><p><strong>Importance: </strong>Invasive fungal infections, including those caused by <i>Candida</i> species, are a persistent global health problem, and their treatment is hindered by limited antifungal options and the emergence of drug resistance. There is an urgent need for tools and methods to accelerate the discovery of novel therapeutic targets. The expanded and optimized auxin-inducible degron system described herein provides a versatile platform for characterizing protein function and dissecting pathways governing important traits like virulence, stress tolerance, and antifungal resistance. The new reagents make AID technology applicable to any strain. Ultimately, this enhanced toolkit has the potential to help identify and validate new high‑value drug targets and deepen our understanding of molecular mechanisms that drive pathogenicity of <i>Candida</i> and other fungal pathogen species.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0035926"},"PeriodicalIF":4.0,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621846/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148795885","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":"Metagenomic sequencing detects viruses and bacteria in a cross-sectional clinical cohort of undifferentiated febrile illness in Nigeria.","authors":"Grace J Vaziri, Julia C Pritchard, Jillian I Howard, Grace E Stamm, David H O'Connor, Christina M Newman, Matthew T Aliota, Asabe Dzikwi-Emennaa","doi":"10.1128/msphere.00157-26","DOIUrl":"10.1128/msphere.00157-26","url":null,"abstract":"<p><p>Molecular and microscopy-based diagnostic capacity is often insufficient or unavailable in places where infectious disease burdens are highest, such as in West Africa. Rapid diagnostic testing (RDT) can provide quick and affordable diagnoses of common infections but is an imperfect solution due to limitations around detecting and dealing with false-negative and false-positive results. An alternative to RDT is unbiased metagenomic sequencing for pathogen surveillance. Here, we present data from unbiased metagenomic sequencing used to identify causes of undiagnosed febrile illness in Jos, Plateau State, Nigeria. Proof of concept for this approach has been demonstrated by several groups who have identified epidemic and endemic viral diseases like Lassa fever, yellow fever, and chikungunya. We show that unbiased deep sequencing and metagenomic analysis can be used to identify RNA viruses in clinical samples. We sequenced RNA from sera of patients (<i>n</i> = 343), many of whom were acutely febrile (76%), in a survey of clinics in Jos. We detected five human-infecting viruses in 39 (11 %) specimens. Among these were hepatitis B virus, human pegivirus, and several anelloviruses. While most of the viruses identified are unlikely to cause clinical symptoms in the patients we sampled, their presence demonstrates the validity of our approach. Additionally, our sequencing data allowed us to identify genetic material from potentially pathogenic bacteria, another possible etiological agent of febrile illness.</p><p><strong>Importance: </strong>In low-resource areas, fevers due to infectious pathogens are a major source of illness, but tools for detecting and identifying such pathogens are often limited. Unbiased approaches for identifying genetic material from all potentially infectious organisms in a sample represent an opportunity for discovering sources of fever. Metagenomic sequencing can improve insight into pathogen landscapes in low-resource settings, potentially providing early detection of disease outbreaks. However, unbiased metagenomic sequencing (mNGS) is no panacea; it is susceptible to contamination and false positives. We used mNGS to evaluate serum from >300 Nigerian clinic-goers in Jos, Nigeria, most of whom (>70%) had fevers of unknown origin. Our goal was to understand arbovirus prevalence in Jos, Nigeria, and identify the sources of infection not routinely monitored for at clinics. We detected hepatitis B virus, as well as nonpathogenic anelloviruses. Our study provides insight into the utility and limitations of mNGS for pathogen surveillance.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0015726"},"PeriodicalIF":4.0,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621840/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148713353","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":"Eosinophil-driven immunopathology exacerbates SARS-CoV-2 pneumonia in an OVA-induced airway allergy mouse model.","authors":"Takao Iketani, Naoko Iwata-Yoshikawa, Yusuke Sakai, Nozomi Shiwa-Sudo, Seiya Ozono, Kaya Miyazaki, Tadaki Suzuki, Noriyo Nagata","doi":"10.1128/msphere.00123-26","DOIUrl":"https://doi.org/10.1128/msphere.00123-26","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Asthma is an allergic airway disease characterized by distinct immune environments that can alter host responses to respiratory viral infections; however, its impact on coronavirus disease 2019 (COVID-19) severity remains unclear. To investigate how allergic airway inflammation affects severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced pneumonia, we used an ovalbumin (OVA)-induced airway allergy mouse model and infected mice with QHmusX, a mouse-passaged SARS-CoV-2 strain that causes severe acute pneumonia. Compared with phosphate-buffered saline-treated controls, OVA-sensitized mice exhibited persistent weight loss, a shift toward prominent alveolar involvement by viral infection, increased inflammatory cell infiltration, and higher histopathological scores, despite comparable viral burden. Enhanced apoptosis and increased numbers of CC10-positive epithelial cells indicated pronounced epithelial injury and repair responses in allergic mice. The post-infection decline in tissue eosinophils, together with histological evidence of eosinophil degranulation and lung cytokine profiling, was associated with amplified inflammatory and granulocyte-associated mediator responses in the airways. To define the functional contribution of eosinophils, we depleted eosinophils using an anti-interleukin-5 monoclonal antibody. Eosinophil depletion improved weight recovery, attenuated lung inflammation, and reduced CC10-associated repair responses without altering viral load. These findings demonstrate that airway allergy exacerbates SARS-CoV-2-induced pneumonia through eosinophil-mediated immunopathology and identify eosinophils as key contributors to disease severity. Targeting eosinophilic inflammation may therefore represent a potential therapeutic strategy for allergic individuals with COVID-19.IMPORTANCEAirway allergy profoundly alters host immunity; however, its impact on coronavirus disease 2019 severity remains unresolved. Using an ovalbumin-induced airway allergy mouse model, we show that pre-existing allergic airway inflammation exacerbates severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced pneumonia despite comparable viral burden. Allergic mice exhibited rapid eosinophil degranulation accompanied by extracellular eosinophil cationic protein deposition, amplified inflammatory mediator responses, and increased epithelial injury. Depletion of eosinophils with anti-interleukin-5 improved weight recovery and lung pathology without measurably affecting viral burden, supporting a pathogenic role for eosinophils in disease exacerbation. These findings indicate that the allergic airway environment can redirect the pulmonary response to SARS-CoV-2 infection and promote immunopathology independently of increased viral replication. The study provides a mechanistic framework for understanding how active allergic inflammation may contribute to severe viral pneumonia and supports further evaluation of eosinophil-targeted ther","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0012326"},"PeriodicalIF":4.0,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149069887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Plasmid-mediated regulation of chromosomal gene expression and virulence in <i>Chlamydia psittaci</i>.","authors":"Yixin Mo, Buwei Wang, Junjun Jia, Xiaomin Lin, Lin Li, Xiaoxin Pan, Kensuke Shima, Chuan Wang, Chunfu Yang","doi":"10.1128/msphere.00507-26","DOIUrl":"https://doi.org/10.1128/msphere.00507-26","url":null,"abstract":"<p><p><i>Chlamydia psittaci</i> (<i>Cps</i>) causes psittacosis, a zoonotic disease characterized by severe pneumonia and systemic infection, yet its pathogenic mechanisms remain poorly understood. While plasmids are established virulence determinants in <i>C. trachomatis</i> (<i>Ct</i>) and <i>Chlamydia muridarum</i> (<i>Cm</i>), their role in <i>Cps</i> pathogenesis is unknown. Here, we generated a panel of <i>Cps</i> transformants with individual deletions of plasmid genes (pgp1-pgp8) and characterized <i>in vitro</i> and <i>in vivo</i>. Genetic analysis revealed that Pgp1 and Pgp2 are required for plasmid maintenance, whereas Pgp3-Pgp8 are dispensable. Transcriptomic and qRT-PCR analyses identified a subset of chromosomal genes regulated by the <i>Cps</i> plasmid, distinct from those described in <i>Ct</i> and <i>Cm</i>. Pgp4 functions as a central regulator of chromosomal gene expression; however, unlike <i>Ct</i> or <i>Cm</i>, Pgp4 does not affect pgp3 transcript levels but is required for Pgp3 protein expression, indicating post-transcriptional regulation. We further show that Pgp7 positively regulates plasmid-dependent gene expression, whereas Pgp6 and Pgp8 negatively regulate this process. Functionally, the plasmid is a determinant of virulence in a murine lung infection model. Pgp3 is essential for host inflammatory responses and bacterial virulence <i>in vivo</i>. Collectively, these findings demonstrate plasmid-mediated regulation in <i>Cps</i> is distinct from that in other chlamydial species and highlight species-specific regulatory mechanisms underlying chlamydial pathogenesis.</p><p><strong>Importance: </strong><i>Chlamydia psittaci</i> is a zoonotic pathogen that causes severe and fatal pneumonia in humans, yet its molecular pathogenesis remains poorly understood. Here, we generated a series of <i>Cps</i> transformants carrying individual ORF deletion and characterized their functions both <i>in vitro</i> and <i>in vivo</i>. We show that Pgp4 and Pgp7 positively regulate a subset of chromosomal genes, whereas Pgp6 and Pgp8 act as negative regulators. Unexpectedly, Pgp4 regulates the major virulence factor Pgp3 at a post-transcriptional level, revealing a previously unrecognized mode of plasmid control. These findings provide new insights into the roles of plasmid-encoded genes in <i>Cps</i> biology and pathogenesis.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0050726"},"PeriodicalIF":4.0,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149069856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Accelerating research to keep pace with the rising incidence of coccidioidomycosis.","authors":"Christina M Homer","doi":"10.1128/msphere.00082-26","DOIUrl":"https://doi.org/10.1128/msphere.00082-26","url":null,"abstract":"<p><p>The number of infections caused by the fungal pathogen <i>Coccidioides</i> is rising. In tandem, the number and breadth of researchers studying this important dimorphic fungal pathogen are growing as well. This review focuses on recent advances in the field and identifies areas primed for ongoing rapid growth, with the goal to improve treatments for coccidioidomycosis as soon as reasonably possible. These areas include building genetic tools, high-throughput drug screening, developing immunomodulatory therapies for coccidioidomycosis, and incorporating research methodologies that can be performed outside of the biosafety level 3 laboratory.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0008226"},"PeriodicalIF":4.0,"publicationDate":"2026-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149040057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"<i>Brucella abortus</i> egresses from host cells in infective clusters through an actin-dependent mechanism.","authors":"José Fabio Campos-Godínez, Alejandro Hernández-Saborío, Tiffany Vargas-Moya, Valeria Gómez-Vargas, David Espinoza-Villagra, Ignacio Sandoval, María Paula Rojas-Salas, Melany López-Hernández, Rodrigo Vega-Arce, Reynaldo Pereira-Reyes, Monica Prado, Carlos Chacón-Díaz, Edgardo Moreno, Esteban Chaves-Olarte, Pamela Altamirano-Silva","doi":"10.1128/msphere.00450-26","DOIUrl":"10.1128/msphere.00450-26","url":null,"abstract":"<p><p><i>Brucella abortus</i> is an intracellular pathogen whose cell cycle encompasses attachment, internalization, trafficking, replication, and egress from host cells. Although the intracellular life of <i>Brucella</i> has been extensively studied, the mechanisms underlying its exit from host cells remain unclear. In this work, we expand the knowledge of this intracellular step by observing a significant increase in the formation of <i>Brucella</i>-containing vacuoles with autophagic features (aBCVs) and abundant <i>B. abortus</i> extracellular clusters (BECs) after 72 h of infection. Membrane extensions protruding through actin polymerization were evident in cells at later stages of infection. Purified aBCVs and BECs were similar in size and predominantly acidic. These vacuoles exhibited a compact arrangement of well-ordered bacteria, comprising a heterogeneous population of dead and live bacteria and host components, including LAMP-1 and actin filaments. A proportion of BECs were enclosed within an impermeable host membrane, while others were not. The actin cytoskeleton was implicated in the protrusion of BECs, since modulation of Rho GTPases affected intracellular aBCV formation and the egress of BECs. BECs protruding from cells invaded uninfected cells, initiating a new cycle of infection. The topological structure and function of BECs underscore their significance in the <i>Brucella</i> life cycle as vehicles for bacterial dissemination to host cells and organs.IMPORTANCE<i>B. abortus</i> is an intracellular pathogen that traffics to the endoplasmic reticulum, where it replicates. However, the mechanisms by which <i>Brucella</i> exits host cells and infects new ones remain poorly understood. Our findings reveal that protruding acidic autophagic-like vesicles containing compact, well-organized <i>Brucella</i> clusters are shed from cells via the GTPase-dependent recruitment of actin filaments. Through this process, the vesicles are impermeable to antibodies and other substances, like antibiotics, and are highly infectious to neighboring cells. This mechanism enhances the understanding of the well-known <i>Brucella</i> stealth strategy to evade the immune system and establish harmful, long-lasting infections.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0045026"},"PeriodicalIF":4.0,"publicationDate":"2026-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149040080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}