mBio最新文献

{"title":"CRISPRi targeting to the <i>Neisseria gonorrhoeae</i> R-loop or G4 mutant region restores pilin antigenic variation.","authors":"Selma Metaane, H Steven Seifert","doi":"10.1128/mbio.01347-26","DOIUrl":"10.1128/mbio.01347-26","url":null,"abstract":"<p><p><i>Neisseria gonorrhoeae</i> pilin antigenic variation (pilin Av) is a complex diversity generation system. Pilin Av depends on a Rec-dependent gene conversion event initiated by an R-loop (<i>gar</i> sRNA) and a resultant G-quadruplex (G4) DNA structure. Mutations of the <i>garP</i> promoter or the G4-forming sequence each prevent pilin Av. We targeted a Type I-C CRISPR interference (CRISPRi) complex to the mutant <i>garP</i> or G4 loci, and CRISPRi targeting to a specific location on the leading strand restored pilin Av. In contrast, targeting the CRISPRi complex to other locations on either the leading or lagging strand was lethal. The CRISPRi restoration of pilin Av depended on the standard recombination factors, confirming the conserved pathway. Inverting the <i>garP-G4</i> region confirmed that the target strand dictates viability and Av outcome. Together, these results reveal that we can replace the R-loop and resultant G4 structure by specific CRISPRi targeting, providing insights into nucleic acid, secondary structure-dependent genome dynamics.IMPORTANCE<i>Neisseria</i>'s pilin antigenic variation remains one of the most sophisticated DNA diversification processes in bacteria, yet the trigger that initiates recombination remains unclear. Here, we show that targeting a Type I CRISPR interference complex is sufficient to restore pilin variation in strains unable to form an R-loop or a G-quadruplex structure. Our findings reveal that the position and strand of R-loop formation, rather than its precise sequence context, determine whether cells undergo antigenic variation, remain viable, or die. This establishes a new framework in which localized topological stress, not a particular DNA structure, plays a role in <i>Neisseria gonorrhoeae</i> pilin antigenic variation.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0134726"},"PeriodicalIF":5.4,"publicationDate":"2026-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13463697/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148391418","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":"Importance of manganese uptake in uropathogenic <i>Escherichia coli</i> CFT073 during urinary tract infection.","authors":"A E Frick-Cheng, O O Adesunloro, B Cobine, H Heithoff, S N Smith, H L T Mobley, A E Shea","doi":"10.1128/mbio.03395-25","DOIUrl":"10.1128/mbio.03395-25","url":null,"abstract":"<p><p>Urinary tract infections (UTIs) are the second most common bacterial infection, with the majority of cases caused by uropathogenic <i>Escherichia coli</i> (UPEC). To establish infection, UPEC requires iron and other transition metals to support essential metabolic processes. In response, the host limits access to these metals during infection, generating a nutrient-restricted environment that pathogens must overcome. We investigated the role of three iron transport systems, Sit, Feo, and Efe, in the prototypical UPEC strain CFT073 during UTI. In the murine model of infection, loss of Sit, but not Feo or Efe, resulted in a significant fitness defect in the urine. Because Sit can transport both iron and manganese, we hypothesized that its contribution to virulence extends beyond iron import. Consistent with this idea, deletion of <i>sitABCD</i> (Δ<i>sit</i>) or both <i>sitABCD</i> and an additional manganese transporter <i>mntH</i> (Δ<i>sit/</i>Δ<i>mntH</i>) impaired growth in metal-restricted minimal medium. Interestingly, <i>mntH</i> deletion increased <i>sitA</i> transcription, but the inverse was not observed, suggesting compensatory regulation under cationic-limiting conditions. All three mutants (Δ<i>sit</i>, Δ<i>mntH</i>, and Δ<i>sit/</i>Δ<i>mntH</i>) displayed significant sensitivity to hydrogen peroxide-induced killing, with the double mutant exhibiting the strongest defect. In the murine model of ascending UTI, the Δ<i>sit/</i>Δ<i>mntH</i> strain was severely attenuated compared to wild type in the urine, bladder, and kidneys. Collectively, these findings demonstrate that manganese uptake, mediated primarily by Sit and MntH, is critical for oxidative stress resistance and bacterial fitness during infection. This highlights the importance of manganese acquisition as a determinant of UPEC pathogenesis in the iron-limited urinary tract.IMPORTANCEUrinary tract infections (UTIs) are one of the most common infectious diseases worldwide, affecting over 50% of women. The primary culprit of uncomplicated UTIs is uropathogenic <i>Escherichia coli</i> (UPEC). Antibiotics are the standard therapy for treating UTIs; however, UPEC is steadily accumulating antibiotic resistance, increasing multidrug resistance. This increasing resistance severely complicates the clinical management of UTIs and requires alternative treatments. This study demonstrates that manganese transporters confer a critical fitness benefit to UPEC during UTI. Manganese acquisition allows UPEC to resist host attack; thus, targeting manganese uptake may lead to new strategies to combat difficult-to-treat UTIs.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0339525"},"PeriodicalIF":5.4,"publicationDate":"2026-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13463694/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148339259","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>Candida</i> spp. suppress neutrophil reactive nitrogen species to evade killing.","authors":"Thomas B Burgess, Ffion R Hammond, Piotr T Szkuta, Amy Lewis, Stella Christou, Keiran A Bowden, Tihana Bicanic, Lynne R Prince, Kathryn R Ayscough, David G Partridge, Simon A Johnston, Alison M Condliffe, Philip M Elks","doi":"10.1128/mbio.00202-26","DOIUrl":"10.1128/mbio.00202-26","url":null,"abstract":"&lt;p&gt;&lt;p&gt;&lt;i&gt;Candida albicans&lt;/i&gt; is a human commensal that can cause life-threatening invasive infection in immunocompromised individuals. Human immunity to &lt;i&gt;C. albicans&lt;/i&gt; infection is thought to be largely dependent on neutrophil reactive oxygen and nitrogen species (ROS/RNS) generation by neutrophils. Despite this, our understanding of innate immune killing and escape by &lt;i&gt;C. albicans&lt;/i&gt; is primarily studied in macrophages, and the precise mechanisms of evasion are unclear in neutrophils. Here, we sought to determine the importance of neutrophil reactive nitrogen species (RNS) production during &lt;i&gt;C. albicans&lt;/i&gt; infection &lt;i&gt;in vivo&lt;/i&gt;. Using a zebrafish model, we found that &lt;i&gt;C. albicans&lt;/i&gt; rapidly downregulated neutrophil RNS below basal levels during the first day post-infection, a time at which neutrophil RNS is upregulated in bacterial infections as an important host-defense mechanism, indicating fungal evasion of host neutrophils. We confirmed the downregulation of RNS in human primary neutrophils and with clinical &lt;i&gt;Candida&lt;/i&gt; isolates, including emerging human pathogens &lt;i&gt;Candida auris&lt;/i&gt; and &lt;i&gt;Candida glabrata&lt;/i&gt;. Inducible nitric oxide synthase (iNOS; Nos2 in zebrafish), the enzyme responsible for RNS production, competes with the arginase enzyme for a shared substrate, L-arginine. Using a zebrafish &lt;i&gt;arginase2&lt;/i&gt; transgenic line and a &lt;i&gt;C. albicans car1&lt;/i&gt;Δ mutant, we showed that both host and fungal arginase contribute to the reduction in neutrophil RNS. Despite pathogen downregulation, upregulation of neutrophil RNS via hypoxia-inducible factor 1α (Hif-1α) stabilization was sufficient to improve host survival following &lt;i&gt;C. albicans&lt;/i&gt; infection. Inhibition of Nos2 blocked the host protective effect of Hif-1α stabilization. Finally, restoration of neutrophil RNS via Hif-1α stabilization was additive to clinically relevant antifungal treatment, increasing survival and clearance of &lt;i&gt;C. albicans&lt;/i&gt; infections. Together, these data demonstrate that restoration of the neutrophil RNS response in &lt;i&gt;C. albicans&lt;/i&gt; infection improves infection outcomes, highlighting the potential of targeting Hif-1α and RNS in host-directed therapies against fungal infections.IMPORTANCE&lt;i&gt;Candida albicans&lt;/i&gt; is a fungus that normally lives harmlessly in the human body but can cause life-threatening infections in people with weakened immune systems. A key part of the body's defense against this fungus is neutrophils, immune cells that kill microbes using toxic molecules. However, how &lt;i&gt;Candida&lt;/i&gt; avoids neutrophil defense is not well understood. Here, we used zebrafish and human immune cells to show that &lt;i&gt;Candida&lt;/i&gt; suppresses an important neutrophil defense, reactive nitrogen species (RNS), during infection. Unlike bacteria, which trigger RNS, &lt;i&gt;Candida&lt;/i&gt; reduces these protective molecules to below normal levels, helping its survival. This effect was also observed with other disease-causing &lt;i&gt;Candida&lt;/i&gt; species. We went on","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0020226"},"PeriodicalIF":5.4,"publicationDate":"2026-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13464021/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148391397","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":"Identification of SKI-II as a host-protective immunomodulator against <i>Staphylococcus aureus</i> infection.","authors":"Liyang Zhang, Kai Ye, Charilaos Dellis, Lewis Oscar Felix, Narchonai Ganesan, Biswajit Mishra, Aijun Zhang, Dale J Hamilton, Yizhi Jane Tao, Eleftherios Mylonakis","doi":"10.1128/mbio.01558-26","DOIUrl":"https://doi.org/10.1128/mbio.01558-26","url":null,"abstract":"<p><p>Antibiotic resistance threatens the effectiveness of conventional antimicrobial agents, underscoring the need for host-directed therapies that enhance immune defense. Here, we present a cross-species discovery pipeline that couples a <i>Caenorhabditis elegans-Staphylococcus aureus</i> liquid-based infection screen with mammalian mechanistic validation to identify small-molecule immunomodulators. Using six <i>C. elegans</i> innate immunity reporter strains, we identified a known small molecule, SKI-II, as a previously unrecognized host-protective compound that activates the <i>C. elegans</i> SKN-1/Nrf2 oxidative-stress pathway. In mouse RAW264.7 macrophages, SKI-II binds to the ATPase pocket of VCP (Valosin-Containing Protein), activating the PERK-dependent (Protein kinase R [PKR]-like Endoplasmic Reticulum Kinase) Nrf2 signaling regulation axis that reduces the levels of pathogenic ROS (reactive oxygen species). SKI-II treatment also promotes macrophage M1 polarization and a mitochondrial metabolic shift. This work identifies VCP as a druggable node for host-directed immunomodulation and highlights SKI-II as a prototype small molecule that boosts host tolerance to infection, thereby validating our <i>C. elegans</i>-based screening platform for discovering immunomodulators active in mammalian systems.IMPORTANCEEnhancing host immunity is a promising strategy to combat <i>S. aureus</i> infection, particularly multidrug-resistant strains. In this study, we applied a <i>C. elegans</i> liquid-based infection screening model to identify the immunomodulatory compound SKI-II. We demonstrate that SKI-II protects against <i>S. aureus</i> infection in both nematodes and mouse macrophages by regulating host oxidative stress pathways rather than directly targeting the pathogen. We reveal a regulatory circuit in which VCP functions as a central node controlling cellular ROS responses and activating the downstream PERK-dependent Nrf2 antioxidant signaling pathway. These findings advance our understanding of host cellular responses to bacterial infection and highlight VCP as a druggable target for host-directed therapeutic strategies against infectious diseases.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0155826"},"PeriodicalIF":5.4,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148701663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"mGem: Dentistry is strategically positioned yet underleveraged in the battle against antimicrobial resistance.","authors":"Jonathon L Baker, Ulf R Dahle, Fernanda C Petersen","doi":"10.1128/mbio.00647-26","DOIUrl":"https://doi.org/10.1128/mbio.00647-26","url":null,"abstract":"<p><p>Dentists account for roughly 10% of global antibiotic prescriptions and maintain a substantial patient contact footprint. As a result, dentistry is strategically positioned in the global response to the antimicrobial resistance (AMR) crisis, offering unique opportunities to impact antibiotic stewardship, AMR surveillance, and infection prevention. However, these opportunities are underleveraged because antibiotic stewardship is insufficiently emphasized in dental education curricula and competencies, and because dentistry is inconsistently integrated into AMR policy and national action plans. This disconnect perpetuates fragmentation in prescribing practices and weakens the alignment of dentistry with global One Health efforts. Furthermore, it leaves dentistry alienated from broader AMR research, funding, and educational frameworks. Specific integration of dentistry into AMR National Action Plans and implementation of unified, research-supported prescribing guidelines, targeted clinician education, and oral resistome surveillance could help transform dentistry from a blind spot to a fulcrum in the global AMR response.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0064726"},"PeriodicalIF":5.4,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148701669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ecology of protection: probiotic biogeography and sepsis prevention in the neonatal intestine.","authors":"Sierra C Hansen, Christopher W Hamm, Jeffrey R Singer, Casey T Weaver, Michael J Gray","doi":"10.1128/mbio.01127-26","DOIUrl":"10.1128/mbio.01127-26","url":null,"abstract":"<p><p>Neonatal infection is a leading cause of morbidity and mortality worldwide, particularly among preterm and low birth weight infants. Probiotic bacteria are widely used in peri- and postnatal care and can reduce neonatal intestinal dysbiosis. However, formulations and efficacy remain highly variable, highlighting a critical gap in our understanding of the mechanisms that drive successful interventions in this population. Furthermore, current studies on probiotic efficacy rely on indirect or relative measures of intestinal bacterial burden. Here, we directly mapped the biogeography of intestinal colonization and quantified the probiotic effects of <i>Escherichia coli</i> Nissle 1917 (EcN) and <i>Ligilactobacillus murinus</i> strain V10 against <i>Klebsiella pneumoniae</i> dysbiosis across the neonatal murine intestine. Despite substantial differences in their spatial distribution along the intestine, both EcN and <i>L. murinus</i> V10 significantly reduced <i>K. pneumoniae</i> colonization and mortality from <i>K. pneumoniae</i> sepsis, with EcN providing greater protection. EcN's probiotic activity was partially dependent on high-affinity oxygen respiration, implicating luminal oxygen availability as a key ecological determinant of probiotic efficacy. Contrary to the common assumption that multi-strain probiotics are inherently superior, simultaneous administration of EcN and <i>L. murinus</i> V10 was less effective than EcN treatment alone at preventing sepsis-related death. These findings identify intestinal niche occupancy, oxygen utilization, and strain-strain interactions as critical variables which should inform the rational design of future probiotic interventions for high-risk neonates.IMPORTANCELate-onset sepsis (LOS) remains a devastating and difficult-to-treat complication of prematurity, and probiotics are increasingly used to reduce dysbiosis and infection risk in this vulnerable population. Probiotic regimens, however, are highly heterogeneous, and their mechanisms of action in the neonatal intestine are poorly defined, complicating efforts to design safe, effective, and regulatable interventions. In this work, we use a neonatal mouse model of LOS to rigorously test fundamental assumptions underlying the current paradigm for understanding the impact of probiotics on intestinal disease. We demonstrate that two distantly related probiotic bacteria, <i>Escherichia coli</i> Nissle 1917 and <i>Ligilactobacillus murinus</i> V10, each reduce intestinal colonization and mortality caused by the LOS pathobiont <i>Klebsiella pneumoniae</i>, but do so through distinct ecological and molecular mechanisms. These findings highlight ecological principles, including spatial niche occupancy, resource competition, and strain-strain interactions, as critical determinants of probiotic efficacy, and provide mechanistic insight that will be important for guiding rational probiotic strategies for high-risk neonates.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0112726"},"PeriodicalIF":5.4,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148701654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Systematic mapping of insertion-tolerant regions enables capsid engineering of an infectious RNA phage.","authors":"Shin-Yae Choi, Min-Ju Kim, Oh Hyun Kwon, Chanseop Park, Hee-Won Bae, Hongbaek Cho, You-Hee Cho","doi":"10.1128/mbio.01639-26","DOIUrl":"https://doi.org/10.1128/mbio.01639-26","url":null,"abstract":"<p><p>RNA phages are attractive platforms for the design of programmable bioparticles, but their development has been constrained by limited knowledge of genomic sites that can tolerate sequence insertion. Here, we combined MuA transposase-mediated <i>in vitro</i> insertion mutagenesis with our established reverse genetics systems to systematically identify insertion-tolerant regions (ITRs) in the RNA phages MS2 and PP7. Screening of 4,555 MS2 and 2,228 PP7 random insertion clones identified 29 and 26 non-redundant ITRs, respectively. We further analyzed and compared these ITRs in the context of RNA genome organization and virion architecture. Both phages contained ITRs within the maturation protein, whereas only PP7 tolerated insertions within the coat protein (CP). On the basis of structural location and plaque-forming capacity, an ITR situated between Gly74 and Glu75 (GGC^GAG) in the PP7 CP was selected for further study. Infectious phage particles generated from complementary DNA clones retained the 15-bp insertion at both the RNA and protein levels. Engineered PP7 phages carrying an Arg-Gly-Asp motif inserted into the CP at this ITR displayed enhanced <i>in vivo</i> clearance in a <i>Drosophila</i> model, despite having <i>in vitro</i> stability comparable to that of the wild type. These findings provide the first example of CP engineering in an infectious RNA phage and establish a framework for engineering RNA phages for biological and biotechnological applications.IMPORTANCEA major obstacle to developing RNA phages as synthetic biology platforms is the lack of design principles for genomic insertion. Here, we address this limitation by establishing a mutagenesis-and-recovery workflow that systematically identifies insertion-tolerant regions (ITRs) in the RNA phages MS2 and PP7. The resulting maps reveal distinct structural constraints in the two phages and enable rational engineering of a peptide-display site in the PP7 capsid. Using this approach, we generated an engineered infectious phage with a modified capsid, thereby providing the first demonstration of capsid engineering in an infectious RNA phage, to our knowledge. This study lays the groundwork for the rational design of live RNA phage virions as tractable and engineerable scaffolds for future biological and biotechnological applications.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0163926"},"PeriodicalIF":5.4,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148701674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deletion of the <i>Salmonella</i> pathogenicity island 2 gene, <i>spiC</i>, in attenuated <i>Salmonella</i> Typhimurium VNP20009 optimizes its potential for bacterial schwannoma therapy.","authors":"Giulia Oliva, Sherif Ahmed, Manlin Shao, John J Mekalanos, Gary J Brenner","doi":"10.1128/mbio.01275-26","DOIUrl":"10.1128/mbio.01275-26","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Recent advances in systems biology and immunotherapy have spurred the investigation of bacteria as therapeutic vehicles for cancer treatment. Currently, Bacillus Calmette-Guérin remains the only FDA-approved bacterial cancer therapy; it is a live attenuated mycobacterium that is indicated for the treatment and prophylaxis of carcinoma &lt;i&gt;in situ&lt;/i&gt; of the urinary bladder and for the prophylaxis of primary or recurrent papillary tumors following transurethral resection. Although safety concerns have been raised, attenuated &lt;i&gt;Salmonella&lt;/i&gt; Typhimurium strains such as VNP20009 have advanced to clinical trials targeting fast-growing human tumors. Notably, this strain induces robust immunological control of slow-growing tumors such as NF2-related schwannomatosis (NF2-SWN) in preclinical murine models. Here, we genetically characterize VNP20009 with the goal of constructing genetically defined attenuated strains that retain its promising therapeutic features while improving safety. Specifically, we investigated the contribution of the &lt;i&gt;Salmonella&lt;/i&gt; pathogenicity island I (SPI-1) and SPI-2 type III secretion systems to antitumor efficacy and biosafety. Mutation of the SPI-1 gene &lt;i&gt;sipB&lt;/i&gt;, a key structural component required for SPI-1 type III secretion system function, partially reduced tumor control in NF2-SWN murine schwannoma models, suggesting that bacterial invasion alone does not fully account for antitumor activity. In contrast, deletion of the SPI-2 gene &lt;i&gt;spiC&lt;/i&gt;, a key effector required for intracellular survival, preserved robust tumor regression in NF2-SWN murine schwannoma models while improving safety and reducing systemic toxicity. To create a genetically defined and tractable platform, we generated two attenuated strains-AST101 and AST101-Δ&lt;i&gt;spiC&lt;/i&gt;-which retain key mutations present in VNP20009 but lack ill-characterized background mutations. In the syngeneic NF2-SWN mouse schwannoma model, both strains significantly suppressed tumor growth compared to PBS. Collectively, these findings support the development of rationally engineered &lt;i&gt;Salmonella&lt;/i&gt; Typhimurium strains with enhanced safety and preserved antitumor efficacy.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Importance: &lt;/strong&gt;Given long-standing safety concerns surrounding the therapeutic use of live bacteria, we constructed a ΔspiC mutant of VNP20009 and demonstrated that it provides a markedly improved safety profile while retaining antitumor efficacy in NF2-related schwannomatosis mouse schwannoma models. In addition, we created two genetically defined &lt;i&gt;Salmonella&lt;/i&gt; Typhimurium strains, AST01 and AST01-ΔspiC, which incorporate the key-targeted mutations found in VNP20009 and VNP20009-ΔspiC, respectively. These engineered strains offer a well-defined genetic background, enabling precise investigation of the bacterial traits responsible for &lt;i&gt;Salmonella&lt;/i&gt; Typhimurium-mediated tumor control and thus further improvement of attenuated strains optimized for bacteriotherapy of neo","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0127526"},"PeriodicalIF":5.4,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148700848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rgg₁₄₄/SHP₁₄₄-controlled streptolancidin D mediates intra-species competition in <i>Streptococcus pneumoniae</i> with cumulative effect from other bacteriocins and fratricide.","authors":"Carina Valente, Sofia Dias, Ozcan Gazioglu, Ana R Cruz, Adriano O Henriques, Hasan Yesilkaya, N Luisa Hiller, Raquel Sá-Leão","doi":"10.1128/mbio.01596-26","DOIUrl":"https://doi.org/10.1128/mbio.01596-26","url":null,"abstract":"&lt;p&gt;&lt;p&gt;&lt;i&gt;Streptococcus pneumoniae&lt;/i&gt; is a major colonizer of the human nasopharynx, where inter- and intra-strain competition plays a critical role in shaping population structure and influencing vaccine outcomes. Bacteriocins are key mediators of intra-species competition, yet many of their functions and regulatory mechanisms remain poorly understood. Here, we identify and characterize streptolancidin D, a previously uncharacterized bacteriocin encoded by the &lt;i&gt;sldA-T&lt;/i&gt; locus, and demonstrate its contribution to pneumococcal competition. Using isogenic streptolancidin-producing and non-producing variants of a naturally colonizing strain, we show that &lt;i&gt;sldA-T&lt;/i&gt; contributes to the inhibition of competitor strains in &lt;i&gt;in vitro&lt;/i&gt; biofilms and during murine co-colonization. Importantly, streptolancidin D also inhibited &lt;i&gt;in vitro&lt;/i&gt; a subset of genetically diverse pneumococcal isolates representing multiple serotypes, whereas non-producing variants showed no activity. This indicates that its effect is broad and not restricted to isogenic interactions. Genomic analysis of over 7,500 pneumococcal genomes revealed that &lt;i&gt;sldA-T&lt;/i&gt; is present in ~12% of isolates, with lineage-associated distribution patterns, and is consistently encoded downstream of the Rgg&lt;sub&gt;144&lt;/sub&gt;/SHP&lt;sub&gt;144&lt;/sub&gt; quorum sensing system. We further demonstrate that &lt;i&gt;sldA-T&lt;/i&gt; is regulated by this system, with &lt;i&gt;sldA-T&lt;/i&gt; promoter activity abolished in a SHP-deficient background and partially restored by exogenous peptide stimulation. Finally, we show that streptolancidin D acts in concert with other bacteriocin systems and competence-mediated fratricide, highlighting a multifactorial antimicrobial strategy that enhances pneumococcal competitiveness. Overall, our findings identify a quorum sensing-regulated bacteriocin that contributes to pneumococcal competition and helps shape population dynamics.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Importance: &lt;/strong&gt;Bacteriocins are central to bacterial competition and niche occupation, particularly in structured environments like the human nasopharynx. While several pneumococcal bacteriocins have been characterized, the functions of many remain unknown, limiting our understanding of how these systems shape strain fitness and population dynamics. We characterize streptolancidin D, a bacteriocin that enhances intraspecies competitiveness &lt;i&gt;in vitro&lt;/i&gt; and &lt;i&gt;in vivo&lt;/i&gt; and contributes to the inhibition of genetically diverse pneumococcal strains. We demonstrate that its expression is tightly regulated by the conserved Rgg&lt;sub&gt;144&lt;/sub&gt;/SHP&lt;sub&gt;144&lt;/sub&gt; quorum sensing system and that the locus is distributed and shows synteny across multiple pneumococcal lineages. Our findings reveal that streptolancidin D operates within a broader network of bacteriocins and competence-associated mechanisms that collectively shape competitive interactions. By integrating genomic, functional, and regulatory analyses, this work expands the known repertoire o","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0159626"},"PeriodicalIF":5.4,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148685132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"<i>Bacillus subtilis</i> YpeB holds SleB inactive, preventing cortex peptidoglycan degradation during spore dormancy.","authors":"Yongqiang Gao, Jeremy D Amon, Joshua C Cofsky, David Z Rudner","doi":"10.1128/mbio.01316-26","DOIUrl":"10.1128/mbio.01316-26","url":null,"abstract":"<p><p>Bacterial endospores are encased in a thick layer of specialized peptidoglycan called the cortex that is essential for core dehydration and heat resistance. Spore germination and outgrowth require cortex degradation by enzymes that are deposited in the spore during sporulation. How these enzymes are held inactive during dormancy and activated during germination remains poorly understood. In <i>Bacillus subtilis</i> and many other endospore-forming bacteria, one of the lytic enzymes, SleB, is encoded in an operon with its putative regulator YpeB. The two proteins depend on each other for stability, but whether and how YpeB inhibits SleB is unknown. AlphaFold predicts a high-confidence interaction between the two proteins, with YpeB's PepSY domains embracing SleB's catalytic domain. Here, we demonstrate that the two proteins can be co-purified when expressed in <i>Escherichia coli</i>. Furthermore, in <i>B. subtilis</i> spores, amino acid substitutions at the predicted SleB/YpeB interface destabilized both proteins, resulting in impaired spore germination in the absence of the functionally redundant cortex lytic enzyme CwlJ. Selection for germination-competent suppressors identified general and allele-specific suppressors in <i>sleB</i> or, separately, <i>ypeB,</i> that stabilized both proteins. Altogether, our data support a model in which YpeB inhibits SleB in the dormant spore through direct interaction. We propose that YpeB's PepSY domains function as chaperone-inhibitors of SleB, akin to the role of pro-domains in protease zymogens. Chaperone dependence ensures that SleB proteins that fail to interact with YpeB remain unfolded and are ultimately degraded, while YpeB-bound SleB enzymes persist but are inhibited, preventing inappropriate cortex degradation during dormancy.</p><p><strong>Importance: </strong>Bacterial spores are among the most resilient cell types in nature. Their ability to resist sterilization during dormancy yet rapidly germinate and resume growth is central to the transmission and pathogenesis of spore-forming pathogens. A key component of their resistance is a thick layer of specialized peptidoglycan called the cortex that encases them. The cortex maintains the spore core in a highly desiccated state by physically restricting its expansion. Germination and outgrowth require the degradation of this essential envelope layer. The enzymes responsible for cortex degradation are deposited in the spore during sporulation. How these lytic enzymes are held inactive during dormancy has been a longstanding question. One of these enzymes, SleB, is encoded in the same operon as its putative regulator YpeB. Here, we provide biochemical and genetic evidence that YpeB interacts with and inhibits SleB during dormancy. These findings lay the groundwork for elucidating how SleB is activated during germination.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0131626"},"PeriodicalIF":5.4,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148685122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}