mBio最新文献

{"title":"mGem: Revisiting bacterial overflow metabolism.","authors":"Niaz Bahar Chowdhury, Wheaton L Schroeder, Lummy Monteiro, Kristin E Burnum-Johnson","doi":"10.1128/mbio.01193-25","DOIUrl":"10.1128/mbio.01193-25","url":null,"abstract":"<p><p>Bacterial overflow metabolism, where cells perform oxidative fermentation despite the availability of ample oxygen and carbon sources, remains a long-standing paradox in microbial metabolism. Traditional explanations attribute this phenomenon to bacterial physiology, including rapid growth, redox imbalances, competitive advantages in microbiomes, and catabolite repression. However, recent advances in systems biology have revealed additional contributing factors, such as thermodynamic constraints, proteome allocation efficiency, bioenergetics, and the membrane real estate hypothesis. Despite these insights, a comprehensive commentary that critically examines these perspectives is still lacking. In this mGem, we summarize key drivers of overflow metabolism, examine state-of-the-art theories, and identify unresolved questions in current understanding. By evaluating multiple viewpoints, we aim to provide a cohesive analysis of bacterial overflow metabolism and contribute to a broader understanding of microbial physiology, regulatory networks, and evolutionary adaptations shaping metabolic strategies.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0119325"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12505891/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144959877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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>Gl</i>Slt2 positively regulates <i>Gl</i>Myb-mediated cellulose utilization in <i>Ganoderma lucidum</i>.","authors":"Zi Wang, Yefan Li, Hao Qiu, Zhouyu Li, Tianyu Ji, Ang Ren, Jing Zhu, Liang Shi, Mingwen Zhao, Rui Liu","doi":"10.1128/mbio.01812-25","DOIUrl":"10.1128/mbio.01812-25","url":null,"abstract":"<p><p>Fungal degradation of cellulose facilitates the sustainable harnessing of biosphere energy and carbon cycling. <i>Ganoderma lucidum</i> is one of the basidiomycetes with the largest number of hydrolytic enzymes in its genome. The mycelium of <i>G. lucidum</i> degrades cellulose through the production of substantial amounts of cellulase, enabling the absorption of carbon sources and nutrients essential for fruiting body development. The efficiency with which <i>G. lucidum</i> utilizes cellulose is a determinant of its growth rate. In this study, our findings revealed that the mitogen-activated protein kinase <i>Gl</i>Slt2 positively modulates cellulase activity and cellulose utilization. Furthermore, a yeast two-hybrid (Y2H) screening library found that <i>Gl</i>Slt2 interacts with <i>Gl</i>Myb, an R2R3-type MYB transcription factor. Further studies revealed that <i>Gl</i>Slt2 phosphorylates the S245 site of <i>Gl</i>Myb and that <i>Gl</i>Myb positively regulates cellulose utilization. <i>Gl</i>Myb directly binds to the [A/G] TTAC [G/C] [C/G] motif on the promoters of cellulase-related genes. The S245 site of <i>Gl</i>Myb promotes the binding of <i>Gl</i>Myb to the promoters of cellulase-related genes. Collectively, our findings highlight the mechanism by which <i>Gl</i>Slt2 positively regulates <i>Gl</i>Myb-mediated cellulose utilization. Enhancing cellulose utilization efficiency lays the foundation for the degradation of cellulose in agricultural and forestry waste and facilitates biomass conversion.</p><p><strong>Importance: </strong>The proficient exploitation of cellulose is pivotal for fostering sustainable development, safeguarding the environment, and advancing economic prosperity and technological innovation. Paramount among these benefits is the reduction of reliance on fossil fuels. <i>Ganoderma lucidum</i>, a filamentous fungus, could effectively utilize cellulose from agricultural and forestry waste. Nevertheless, enhancing the efficiency of cellulose utilization from these by-products presents a formidable challenge that demands resolution. In our study, we discovered that GlSlt2 interacts with GlMyb and phosphorylates the S245 site of GlMyb. Further studies have revealed that GlSlt2 positively regulates GlMyb-mediated cellulose utilization. In summary, our findings unveil a sophisticated regulatory mechanism controlling cellulose utilization. These insights lay the foundation for biomass conversion and the biosphere carbon cycle.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0181225"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12506057/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145015729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution and structural diversity of the MotAB stator: insights into the origins of bacterial flagellar motility.","authors":"Caroline Puente-Lelievre, Pietro Ridone, Jordan Douglas, Kaustubh Amritkar, Betül Kaçar, Matthew A B Baker, Nicholas J Matzke","doi":"10.1128/mbio.03824-24","DOIUrl":"10.1128/mbio.03824-24","url":null,"abstract":"<p><p>The rotation of the bacterial flagellum is powered by the MotAB stator complex, which converts ion flux into torque. Despite its central role in flagellar function, the evolutionary origin and structural diversity of this system remain poorly understood. Here, we present the first comprehensive phylogenetic and structural characterization of MotAB and its closest non-flagellar homologs. We gathered homologs from 205 genomes across 27 bacterial phyla, estimated phylogenies, inferred ancestral sequences, and predicted structures for both extant and inferred ancestral proteins using AlphaFold. Our analyses characterized two structurally distinct groups: flagellar ion transporters (FIT) and generic ion transporters (GIT). FIT proteins are structurally conserved, including a characteristic square fold domain and a torque-generating interface (TGI). We further delineate FIT proteins into two subgroups, TGI4 and TGI5s, based on the presence of 4 or 5 short helices within the TGI region. TGI5 motors, such as those found in the <i>Escherichia coli</i> K12 system, are primarily restricted to Pseudomonadota, whereas TGI4 motors, such as the Na⁺-powered polar motors of <i>Vibrio</i> (PomAB), are distributed across a broader range of bacterial lineages. In contrast, GIT proteins exhibit substantial structural and functional heterogeneity and lack features associated with flagellar motility. Nevertheless, a conserved interaction between the A and B subunits is retained across FIT and GIT proteins, with their corresponding genes typically adjacent to operons. Functional assays in <i>E. coli</i> show that FIT-specific structural elements are indispensable for flagellar motility. Our results suggest that the flagellar stator motor complex evolved once from a common ancestral ion transporter, acquiring unique structural traits to support motility. This work provides a robust framework for understanding the evolutionary diversification of stator complexes and their mechanistic specialization.IMPORTANCEFlagellar motility allows bacteria to propel themselves and direct movement according to environmental conditions. It plays a key role in bacterial pathogenicity and survival. We investigated the molecular and structural diversity of the stator motor proteins that provide the ion motive force to power flagellar rotation. This study uses a comparative approach that integrates phylogenetics, 3D protein structure, motility assays, and ancestral state reconstruction (ASR) to provide insights into the structural mechanisms that first powered the flagellar motor. We provide the first phylogenetic and structural characterization and classification of MotAB and relatives.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0382424"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12505986/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145030087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of antivirus defense in prokaryotes, depending on the environmental virus prevalence and virome dynamics.","authors":"Sanasar G Babajanyan, Sofya K Garushyants, Yuri I Wolf, Eugene V Koonin","doi":"10.1128/mbio.02409-25","DOIUrl":"10.1128/mbio.02409-25","url":null,"abstract":"<p><p>Prokaryotes can acquire antivirus immunity via two fundamentally distinct types of processes: direct interaction with the virus, as in clustered regularly interspaced short palindromic repeats (CRISPR)-Cas adaptive immunity systems, and horizontal gene transfer (HGT), which is the main route of transmission of innate immunity systems. These routes of defense evolution are not mutually exclusive and can operate concomitantly, but observations suggest that at least in some bacterial and archaeal species, one or the other route dominates the defense landscape. We hypothesized that the observed dichotomy stems from different life-history trade-offs characteristic of these organisms. To test this hypothesis, we analyzed a mathematical model of a well-mixed prokaryote population under a stochastically changing viral prevalence. Optimization of the long-term population growth rate reveals two contrasting modes of defense evolution. In stable, predictable environments, direct interaction with the virus is the optimal route of immunity acquisition. In fluctuating, unpredictable environments with a moderate viral prevalence, horizontal transfer of defense genes is preferred. In the HGT-dominant mode, we observed a universal distribution of the fraction of microbes with different immune repertoires. Under very low virus prevalence, the cost of immunity exceeds the benefits such that the optimal state of a prokaryote is complete absence of defense systems. By contrast, under very high virus prevalence, horizontal spread of defense systems dominates regardless of the stability of the virome. These findings might explain consistent but enigmatic patterns in the spread of antivirus defense systems among prokaryotes, such as the ubiquity of adaptive immunity in hyperthermophiles contrasting their patchy distribution among mesophiles.</p><p><strong>Importance: </strong>The virus-host arms race is a major component of the evolutionary process in all organisms that drove the evolution of a broad variety of immune mechanisms. In the last few years, over 200 distinct antivirus defense systems have been discovered in prokaryotes. There are two major modes of immunity acquisition: innate immune systems spread through microbial populations via HGT, whereas adaptive-type immune systems acquire immunity via direct interaction with the virus. We developed a mathematical model to explore the short-term evolution of prokaryotic immunity and showed that in stable environments with predictable viral repertoires, adaptive-type immunity is the optimal defense strategy, whereas in fluctuating environments with unpredictable virus composition, HGT dominates the immune landscape.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0240925"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12505974/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145069911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"mGem: Guides or triggers? Extracellular RNAs beyond vesicular miRNAs.","authors":"Juan Pablo Tosar, Amy H Buck","doi":"10.1128/mbio.03129-24","DOIUrl":"10.1128/mbio.03129-24","url":null,"abstract":"<p><p>Despite a huge expansion in the last decades, several assumptions have directed, and perhaps pigeonholed, the evolution of the extracellular RNA (exRNA) field. For example, extracellular vesicles (EVs) have been assumed to be the main carriers of RNA molecules between cells. In parallel, microRNAs (miRNAs) have been assumed to be the main EV RNA cargo. However, from mammals to microbes, these assumptions do not seem to fall out of the data. In addition, miRNAs need to localize to the cytosol to be active but are likely to start in endosomes in most EV entry pathways. The mechanisms for their endosomal escape and the quantities of imported miRNAs required for their functions are not always considered. Without questioning the empirical evidence supporting EV-miRNA-mediated intercellular communication, we would like to shed light on the overlooked aspects of the exRNA biology that may bear important insights into how cells and organisms interact and sense one another.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0312924"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12505971/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145069922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distinct modes of cell division drive <i>Anaplasma phagocytophilum</i> morphotype development and the infection cycle.","authors":"Travis J Chiarelli, Savannah E Sanchez, Mary Clark H Lind, Nathaniel S O'Bier, Curtis B Read, Richard T Marconi, Jason A Carlyon","doi":"10.1128/mbio.01972-25","DOIUrl":"10.1128/mbio.01972-25","url":null,"abstract":"<p><p>Pleomorphism is an evolutionary adaptation by which diverse microorganisms maximize their fitness by transitioning between morphologically distinct forms that perform disparate functions in response to the local microenvironment. Cell division is critical for morphotype transition in many pleomorphic bacterial systems. <i>Anaplasma phagocytophilum</i>, which causes the emerging disease granulocytic anaplasmosis, is a pleomorphic obligate intracellular bacterium that lives in a pathogen-modified vacuole except for when it is exocytically released for dissemination to naïve cells. This bacterium cycles between non-infectious, replicative reticulate cell (RC) and infectious, non-replicative dense-cored (DC) forms. Here, we establish that differential modes of <i>A. phagocytophilum</i> cell division drive morphotype development where RC bacteria divide symmetrically to expand the intravacuolar population after which they switch to sacrificial asymmetric division to produce DCs. <i>A. phagocytophilum</i> MreB is crucial for cell division, specifically septation, and thereby formation of both morphotypes. Inhibition of cell division prevents not only DC formation but also <i>A. phagocytophilum</i> vacuole maturation and infectious progeny release, which suggests that these pathogenic processes are coordinated. This study advances understanding of <i>A. phagocytophilum</i> growth and morphotype development and, thus, pathobiology. It also provides the first evidence linking cell division to morphotype development in the <i>Anaplasmataceae</i>.IMPORTANCE<i>Anaplasma phagocytophilum</i>, an obligate intracellular bacterial pathogen that lives in a host cell-derived vacuole, causes human and veterinary diseases of global importance. In the pathogen-occupied vacuole, <i>A. phagocytophilum</i> transitions from a replicative, non-infectious morphotype to a non-replicative, infectious morphotype that is released to spread infection. We established that distinct modes of bacterial cell division drive not only <i>A. phagocytophilum</i> replication but also its differentiation to the infectious form and dissemination to naïve cells. How pleomorphism is regulated in most vacuole-adapted bacterial pathogens is poorly understood. Therefore, this study advances fundamental knowledge of vacuole-adapted pleomorphic bacteria pathobiology and could ultimately identify common novel antibiotic targets for treating the diseases they cause.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0197225"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12506133/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144959766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reprogramming resistance: phage-antibiotic synergy targets efflux systems in ESKAPEE pathogens.","authors":"Anita Tarasenko, Bhavya N Papudeshi, Susanna R Grigson, Vijini Mallawaarachchi, Abbey L K Hutton, Morgyn S Warner, Jeremy J Barr, Jon Iredell, Bart Eijkelkamp, Robert A Edwards","doi":"10.1128/mbio.01822-25","DOIUrl":"10.1128/mbio.01822-25","url":null,"abstract":"<p><p>Multidrug-resistant (MDR) and extensively drug-resistant (XDR) ESKAPE pathogens pose a significant global health threat due to their ability to evade antibiotics through intrinsic and acquired mechanisms. These bacteria, including <i>Enterococcus faecium</i>, <i>Staphylococcus aureus</i>, <i>Klebsiella pneumoniae</i>, <i>Acinetobacter baumannii</i>, <i>Pseudomonas aeruginosa</i>, <i>Escherichia coli,</i> and <i>Enterobacter</i> species, evade antibiotics through intrinsic and adaptive mechanisms. Common strategies include capsule formation, biofilm, β-lactamase production, and efflux activity. Using these mechanisms, bacteria can evade the effects of antibiotics, leading to persistent and difficult-to-treat infections. Understanding the mechanisms of resistance is crucial in developing effective strategies to combat MDR and XDR ESKAPEE pathogens. A promising approach is the development of alternative treatments targeting specific resistance mechanisms in these pathogens. Bacteriophages (phages), which co-evolve with bacterial hosts, offer a dynamic therapeutic alternative by targeting pathogenic bacteria using precision-based strategies. This targeted approach can overcome antibiotic resistance and reduce the risk of damaging the beneficial microbiota. Phages can restore susceptibility in previously untreatable infections by enhancing antibiotic uptake and imposing fitness costs on resistant strains. However, therapeutic deployment faces challenges such as rapid evolution of phage resistance, inconsistent production standards, and limited regulatory pathways. This review examines the mechanistic insights into phage-antibiotic synergy, with a focus on efflux pump-mediated resistance. It discusses emerging therapeutic strategies, current clinical applications, and the translational frameworks needed to integrate phage therapy into mainstream medicine and transform the clinical management of drug-resistant ESKAPEE infections.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0182225"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12506008/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145015749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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>Pseudomonas aeruginosa</i> supports the survival of <i>Prevotella melaninogenica</i> in a cystic fibrosis lung polymicrobial community through metabolic cross-feeding.","authors":"Bassam El Hafi, Fabrice Jean-Pierre, George A O'Toole","doi":"10.1128/mbio.01594-25","DOIUrl":"10.1128/mbio.01594-25","url":null,"abstract":"<p><p>Cystic fibrosis (CF) is a multi-organ genetic disorder that affects more than 100,000 individuals worldwide. Chronic respiratory infections are among the hallmark complications associated with CF lung disease, and these infections are often due to polymicrobial communities that colonize the airways of persons with CF (pwCF). Such infections are a significant cause of morbidity and mortality, with studies indicating that pwCF who are co-infected with more than one organism experience more frequent pulmonary exacerbations, leading to a faster decline in lung function. Previous work established an <i>in vitro</i> CF-relevant polymicrobial community model composed of <i>P. aeruginosa</i>, <i>S. aureus</i>, <i>S. sanguinis</i>, and <i>P. melaninogenica. P. melaninogenica</i> cannot survive in monoculture in this model. In this study, we leverage this model to investigate the interactions between <i>P. aeruginosa</i> and <i>P. melaninogenica</i>, allowing us to understand the mechanisms by which the two microbes interact to support the growth of <i>P. melaninogenica</i> specifically in the context of the polymicrobial community. We demonstrate a cross-feeding mechanism whereby <i>P. melaninogenica</i> metabolizes mucin into short-chain fatty acids that are, in turn, utilized by <i>P. aeruginosa</i> and converted into metabolites (succinate, acetate) that are cross-fed to <i>P. melaninogenica</i>, supporting its survival in the CF lung-relevant model. This work highlights the potential metabolic interactions among microbes in CF infections.IMPORTANCEPolymicrobial interactions impact disease outcomes in pwCF who suffer from chronic respiratory infections. Previous work established a CF-relevant polymicrobial community model that allows experimental probing of these microbial interactions to achieve a better understanding of the factors that govern the mechanisms by which CF lung microbes influence each other. In this study, we investigate the interaction between <i>P. aeruginosa</i> and <i>P. melaninogenica</i>, which are two highly prevalent and abundant CF lung microbes. We uncover a mechanism that involves complex cross-feeding between <i>P. aeruginosa</i> and <i>P. melaninogenica</i> to support the growth of the latter.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0159425"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12506151/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145040443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Naturally occurring mutations in envelope mediate virulence of Usutu virus.","authors":"Megan B Vogt, Jeffrey M Marano, William J Hanrahan, Seth A Hawks, Anne M Brown, Sheryl Coutermarsh-Ott, James Weger-Lucarelli, Nisha K Duggal","doi":"10.1128/mbio.01593-25","DOIUrl":"10.1128/mbio.01593-25","url":null,"abstract":"<p><p>Usutu virus (USUV) is a mosquito-transmitted flavivirus that is closely related to West Nile virus. Recently, USUV emerged in Europe, where it has caused multiple bird die-off events and neuroinvasive disease in humans. Previously, we showed that USUV isolates from Africa cause significantly more severe disease than European isolates in mice. Sequence analysis revealed that the most virulent isolate (Uganda 2012) and the least virulent isolate (Netherlands 2016) differed by 21 amino acids across the viral polyprotein. Here, we sought to identify the viral determinants of and mechanisms for differential virulence. To accomplish this, we used our USUV reverse genetics system and bacteria-free cloning to generate chimeric viruses between Uganda 2012 and Netherlands 2016. <i>Ifnar1^-/-</i> mice infected with a Netherlands 2016 chimera containing all of the structural genes, or just the envelope gene, from Uganda 2012 had significantly higher mortality rates and viremia than those infected with wild-type Netherlands 2016. We were unable to identify a single amino acid in the envelope protein that resulted in significantly increased virulence compared to wild-type Netherlands 2016. These results indicate that multiple mutations in USUV envelope protein contribute to differential virulence between isolates. Through <i>in vitro</i> assays, we discovered that envelope mediates replication kinetics, with fusion occurring more slowly for wild-type Netherlands 2016 compared to viruses containing the envelope from Uganda 2012, suggesting a mechanism for envelope-mediated differential virulence of USUV. These studies provide insights into USUV pathogenic mechanisms, which could be used to evaluate the disease potential of related emerging viruses.IMPORTANCEUsutu virus (USUV) is currently emerging in Europe, where it has caused numerous mass bird die-off events and neuroinvasive disease in humans. Multiple strains of USUV are circulating throughout Europe, but only some of them have been associated with severe disease in humans. The USUV proteins responsible for and the mechanisms through which they cause severe disease are unknown; however, this information could be invaluable in evaluating disease potential of specific strains and the creation of anti-viral therapies. Here, we swapped genes between USUV strains that cause mild and severe disease and were able to identify a viral protein that mediates virulence. We also discovered that the mild strain of USUV takes significantly longer to complete fusion during viral entry into host cells than the severe strain. This delayed fusion could have impacts on cellular tropism, viral kinetics, susceptibility of the virus to immune responses, and, ultimately, disease severity.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0159325"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12506040/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145040582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fungal mitochondria govern both gliotoxin biosynthesis and self-protection.","authors":"Patrícia Alves de Castro, Endrews Delbaje, Ivan Lucas de Freitas Migliorini, Monica T Pupo, Muhammad Shafiul Alam Mondal, Karin Steffen, Antonis Rokas, Stephen K Dolan, Gustavo H Goldman","doi":"10.1128/mbio.02401-25","DOIUrl":"10.1128/mbio.02401-25","url":null,"abstract":"<p><p>Gliotoxin (GT) is a potent epipolythiodioxopiperazine toxin produced by the opportunistic pathogen <i>Aspergillus fumigatus</i> that contributes to virulence and inhibits competing microorganisms. However, GT is highly toxic to the producer itself, necessitating robust self-protection mechanisms. Here, we used a comparative transcriptomics approach between <i>A. fumigatus</i> (GT producer) and <i>A. nidulans</i> (non-producer) to identify additional genetic determinants of GT self-protection downstream of the transcription factor RglT. We characterized five RglT-dependent genes: <i>abcC1</i> (ABC transporter), <i>mfsD</i> (major facilitator superfamily transporter), <i>oxrA</i> (oxidoreductase), <i>mtrA</i> (putative methyltransferase), and <i>nmrC</i> (a GATA-type repressor). Deletion mutants in <i>A. fumigatus</i> and <i>A. nidulans</i> revealed that all except <i>oxrA</i> were required for full GT protection, with Δ<i>mtrA</i> and Δ<i>nmrC</i> exhibiting distinct phenotypes in oxidative stress and iron-starvation conditions. Transcriptomic profiling and protein network analysis showed that MtrA and NmrC influence mitochondrial functions, particularly ubiquinone biosynthesis, despite not localizing to mitochondria. Functional assays confirmed that GT exposure disrupts mitochondrial integrity and sensitizes <i>A. fumigatus</i> to mitochondrial inhibitors. Notably, GT-induced cell death was associated with mitochondrial fragmentation but lacked hallmarks of apoptosis-like nuclear damage. Together, our findings reveal new genetic components of GT detoxification and establish a critical role for mitochondrial function in <i>A. fumigatus</i> GT self-protection and production.IMPORTANCEGliotoxin (GT) plays a central role in the pathogenicity of <i>Aspergillus fumigatus</i> by enabling immune evasion and microbial competition, but its extreme toxicity also threatens the fungus itself. Although core GT biosynthetic and detoxification mechanisms are well studied, the full genetic network safeguarding against GT's effects remains incompletely understood. This study identifies new RglT-regulated genes that contribute to GT self-protection and demonstrates that mitochondrial function is crucial for surviving GT exposure. Remarkably, similar protective pathways are active in both GT-producing and non-producing fungi, underscoring the ecological relevance of GT defense mechanisms. These findings deepen our understanding of fungal toxin tolerance and highlight mitochondria as a potential vulnerability that could be exploited for antifungal interventions.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0240125"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12505978/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145040605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}