mBio最新文献

{"title":"<i>Wolbachia</i> uses ankyrin repeats to target specific fly proteins.","authors":"William Hamilton, Erin Hardy, Sergio López-Madrigal, Melissa Phelps, MaryAnn Martin, Irene Newton","doi":"10.1128/mbio.00172-26","DOIUrl":"10.1128/mbio.00172-26","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Arthropods, the most diverse phylum on Earth, are hosts to a plethora of bacterial parasites that secrete various effectors of unknown function during infection. The most prevalent of these is the intracellular bacterium &lt;i&gt;Wolbachia pipientis&lt;/i&gt;. The microbe infects between 40% and 60% of insect species, where it induces a variety of fitness effects ranging from nutritional supplementation to reproductive manipulations and, in some hosts, limiting virus replication. Understanding the molecular basis of &lt;i&gt;Wolbachia&lt;/i&gt; infection and &lt;i&gt;Wolbachia-&lt;/i&gt;induced phenotypes is critical to the use of &lt;i&gt;Wolbachia&lt;/i&gt; in vector control. &lt;i&gt;Wolbachia&lt;/i&gt; ankyrin repeat proteins (WARPs) represent a highly dynamic and diverse part of the &lt;i&gt;Wolbachia&lt;/i&gt; pangenome and remain thus far largely uncharacterized. Here, we perform molecular and genetic screens to identify interactions between &lt;i&gt;Wolbachia w&lt;/i&gt;Mel WARPs and their target host proteins in &lt;i&gt;Drosophila melanogaster&lt;/i&gt;. Our results identify strong interactions of two &lt;i&gt;Wolbachia&lt;/i&gt; proteins, WARP434 and WARP754, with multiple host targets. Heterologous expression of these two WARPs is extremely toxic in &lt;i&gt;Drosophila&lt;/i&gt; tissues, and the toxicity is dependent on the ankyrin repeat domain of each WARP. We use coimmunoprecipitation (coIP) and mass spectrometry to identify native targets of the WARPs, and importantly, knockdown of host targets alleviates toxicity, confirming WARP/target interactions. Antibodies targeting both WARPs show expression by &lt;i&gt;Wolbachia&lt;/i&gt; during infection of &lt;i&gt;Drosophila&lt;/i&gt; cells, and expression of WARP754 in adult flies increases &lt;i&gt;Wolbachia&lt;/i&gt; titer. Understanding how &lt;i&gt;Wolbachia&lt;/i&gt; manipulates its host biology and which host pathways it targets during infection will help us define how the most prevalent intracellular bacterial parasite on Earth interacts with its insect hosts at the molecular level. Our screen is an important step toward that goal.IMPORTANCEMolecular interactions drive co-evolutionary arms races between hosts and pathogens. These interactions shape the structure and function of both host and parasite proteins, enabling immunity or virulence during infection. Understanding the molecular details that unfold during these events illustrates not only how hosts and parasites co-evolve at the molecular level but also may help characterize the function of poorly understood proteins. The most prevalent intracellular infection on earth is &lt;i&gt;Wolbachia pipientis&lt;/i&gt;, with between 40% and 60% of insects harboring the bacterial symbiont. Understanding how Wolbachia infects host cells and the molecular tools it uses to alter cell biology is critical to the use of the microbe in vector control. Here, we identify &lt;i&gt;Wolbachia&lt;/i&gt; proteins used by the symbiont to interface with specific host proteins. Understanding the molecular mechanisms underlying this host-microbe interaction will shed light on how an important symbiont, used in the control of vector","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0017226"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723351","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":"Utilization of a CRISPRi-based <i>ex vivo</i> challenge model to reveal temporally dependent gene essentiality in intracellular <i>Mycobacterium tuberculosis</i>.","authors":"Monique E Theriault, Andrew I Wong, Michael A DeJesus, Davide Pisu, Bom Nae Rin Lee, Greana Kirukubar, Shuqi Li, Joshua B Wallach, Dirk Schnappinger, Gabrielle Lê-Bury, David G Russell, Jeremy M Rock","doi":"10.1128/mbio.00610-26","DOIUrl":"10.1128/mbio.00610-26","url":null,"abstract":"<p><p><i>Mycobacterium tuberculosis</i> (Mtb) remains a leading cause of infectious disease mortality worldwide, largely due to its ability to survive within host macrophages. Despite advances in understanding the environmental pressures Mtb encounters <i>in vivo</i>, the genetic requirements for adaptation and survival within the intracellular niche remain incompletely defined. Here, we employed a genome-wide CRISPR interference (CRISPRi) screen in an <i>ex vivo</i> model exploiting single-cell suspensions from Mtb-infected mouse lung homogenates to identify genes critical for intracellular survival at different time points in the infection continuum. Using a library comprising ~20,000 sgRNAs covering >96% of Mtb open reading frames, we identified genes required for growth within the changing immune microenvironment. Mutant depletion patterns varied across immune environments sampled at 2, 4, and 6 weeks post-infection, which revealed a weighted dependency on cell wall biosynthesis genes early and the reliance on cholesterol catabolism and iron acquisition across all time points. Functional validation of three genes-<i>embB</i>, <i>fadE29</i>, and <i>mbtI</i>-confirmed their temporal significance <i>in vivo</i>. This screen provides increased resolution of the differential metabolic vulnerabilities in Mtb in the evolving immune environments during infection, stressing the temporal nature of conditional essentiality <i>in vivo</i>.</p><p><strong>Importance: </strong><i>Mycobacterium tuberculosis</i> (Mtb) remains a leading cause of infectious disease mortality worldwide, largely due to its ability to survive within host macrophages. Despite advances in understanding the environmental pressures Mtb encounters <i>in vivo</i>, the genetic requirements for adaptation and survival within the intracellular niche remain incompletely defined. Here, we employed a genome-wide CRISPR interference (CRISPRi) screen in an <i>ex vivo</i> model exploiting single-cell suspensions from Mtb-infected mouse lung homogenates to identify genes critical for intracellular survival at different time points in the infection continuum. This novel approach enabled us to identify how different bacterial metabolic pathways were of greater importance to the bacterium at different time points post-infection. The results provide insights into how the evolving immune response to infection shapes the metabolic and replicative status of the bacterium. This information has significance in the design of therapeutic strategies toward cure.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0061026"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723278","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":"Protein QID74 protects the cell wall of <i>Trichoderma</i> from degradation caused by its own chitinase, which lacks a carbohydrate-binding module.","authors":"Jun-Jin Deng, Zhao-Fu Chen, Ming-Shu Zhang, Jing Liu, Zhi-Lin Wang, Jia-Zhou Li, Shaowen Wu, Xiao-Chun Luo","doi":"10.1128/mbio.00018-26","DOIUrl":"10.1128/mbio.00018-26","url":null,"abstract":"<p><p>The fungal cell wall, formed by a chitin backbone, is critical for cellular integrity and environmental fitness. Mycoparasitic fungi of the genus <i>Trichoderma</i> deploy an arsenal of potent chitinases to dismantle the cell walls of prey fungi. However, the mechanisms that safeguard the mycoparasite from self-inflicted enzymatic damage remain poorly understood. While most chitinases possess carbohydrate-binding modules (CBMs) to facilitate substrate recognition, the critical group A chitinase of <i>Trichoderma harzianum</i> is conspicuously CBM-free. In this study, we investigated the evolutionary and functional rationale for this structural omission by comparing native Chit46 with engineered CBM-fused variants. Results demonstrate that while native Chit46 promotes the hyphal growth of <i>T. harzianum</i>, the fusion of a CBM shifts the enzymatic activity from highly specific to self-destructive. CBM-fused variants significantly enhanced the degradation of host cell walls but simultaneously triggered the hydrolysis of <i>Trichoderma</i>'s own hyphae, a phenotype absent in the native enzyme. These findings suggest an evolutionary selection against CBMs in specific chitinases to prevent deleterious autocatalytic activity. Furthermore, QID74 was identified as a critical cell wall-associated \"shield\" protein that specifically binds Chit46 to prevent self-hydrolysis. Structural characterization revealed that QID74 is composed of 13 tandem 59-residue repeats containing conserved tridecapeptide motifs (NGKQCVCPKGQVW). Biochemical validation via His pull-down and isothermal titration calorimetry confirmed that these repetitive units are essential and sufficient for chitinase binding. Our results illuminate a sophisticated \"arrow-and-shield\" mechanism that balances offensive mycoparasitic capabilities with the maintenance of self-integrity, providing new insights into fungal self-recognition and the optimization of microbial biocontrol agents.</p><p><strong>Importance: </strong>This study uncovers a unique survival strategy in <i>Trichoderma</i>. By lacking a carbohydrate-binding module, <i>Trichoderma</i>'s chitinase can effectively degrade host cell walls while minimizing self-damage. The protective protein QID74 further safeguards the cell wall by binding to the chitinase. This research offers novel insights into fungal biology and ecology, with potential applications in developing sustainable biocontrol agents.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0001826"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723344","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":"High-throughput screening reveals mechanisms of environmental control of germination in a fungal thermophile.","authors":"Olusola A Ogunyewo, Kristopher Fleming, Madeleine Morris, Kayleigh Fort, Lori B Huberman, Rachel B Brem","doi":"10.1128/mbio.03907-25","DOIUrl":"10.1128/mbio.03907-25","url":null,"abstract":"<p><p><i>Thermothelomyces thermophilus</i> is a filamentous fungus isolated from self-heating compost. Unlike most of the fungal kingdom, this species exhibits a growth optimum at 45°C and is intolerant of temperatures below 30°C. To investigate genetic contributors to temperature-dependent fitness in this system, we implemented a large-scale insertional mutagenesis approach. We generated thousands of <i>T. thermophilus</i> mutants and cultured them at temperature extremes in a standard medium. Phenotyping-by-sequencing identified dozens of disrupted loci representing candidate determinants of thermophilic life history, including several annotated in metal transport. We then validated a subset of screen hits with a directed, single-gene knockout paradigm. The results revealed a temperature-dependent regulatory logic for germination, the developmental decision by which a fungal spore initiates growth. Surprisingly, most mutants germinated far better at 50°C than the wild type in a standard medium and showed markedly slower germination at lower temperatures, consistent with altered germination regulation rather than enhanced intrinsic heat tolerance. We hypothesized that <i>T. thermophilus</i> has evolved sophisticated regulatory machinery to block germination at high temperatures unless environmental conditions are favorable. As a proof of concept, we surveyed media conditions and established that elevated zinc dampened germination of wild-type <i>T. thermophilus</i> at 50°C but promoted it at lower temperatures; mutation experiments made clear that such sensitivity was mediated in part by the zinc transporter <i>zip</i>. We interpret these results under a model in which <i>T. thermophilus</i> integrates temperature and nutrient availability to control the transition from spore dormancy to vegetative growth, a developmental decision that shapes fitness outcomes across temperatures.IMPORTANCEFungal thermophiles thrive at temperatures that represent the upper limits of eukaryotic life. The regulatory and developmental mechanisms that shape their temperature-dependent fitness remain poorly understood. In this work, we elucidate how <i>Thermothelomyces thermophilus</i> integrates temperature cues with other environmental inputs during germination, a key life-cycle stage for dispersal. Our findings highlight germination regulation as an important contributor to fitness at elevated temperatures in a thermophilic eukaryote. These insights are of basic biological interest and provide a foundation for rational strategies to modulate temperature-dependent performance in industrial strains, with applications for high-temperature bioprocessing.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0390725"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723334","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>Staphylococcus aureus</i> can degrade exogenous fatty acids through β-oxidation.","authors":"Cindy Menjivar, Clarissa Shoffler, Christopher Petucci, Jeffrey L Bose","doi":"10.1128/mbio.00609-26","DOIUrl":"10.1128/mbio.00609-26","url":null,"abstract":"<p><p><i>Staphylococcus aureus</i> has long been thought to lack a functional fatty acid degradation (Fad) pathway despite the presence of a locus annotated with the necessary <i>fad</i> genes; however, two recent studies have examined the <i>fad</i> operon for the first time. While they provided key insights about the system and both identified that exogenous fatty acids can be added to coenzyme A to produce an acyl-CoA, neither identified whether degradation occurs. The <i>fad</i> operon contains two sizeable intergenic regions even though the <i>fadXDEBA</i> genes can be expressed on a single polycistronic mRNA under the control of the <i>fadX</i> promoter. We hypothesized that these intergenic regions could be a point of regulation that prevents full Fad function; therefore, we generated a new <i>S. aureus</i> strain where the two intergenic regions of the <i>fadXDEBA</i> operon were deleted. Using mass spectrometry analysis with this strain, we detected degradation products from both palmitic acid and oleic acid, a saturated and unsaturated fatty acid, respectively. The products were absent in a <i>fadXDEBA</i> mutant. These data demonstrate that the <i>S. aureus</i> fatty acid degradation system is functional and can degrade exogenous fatty acids.IMPORTANCEThere have been limited studies on the fatty acid degradation (Fad) pathway of <i>Staphylococcus aureus</i>. The <i>fadXDEBA</i> operon has been shown to contain all the genes necessary for β-oxidation, and the FadD and FadBA proteins have been shown to perform their canonical functions. This study demonstrates that the full <i>S. aureus</i> Fad pathway is functional and capable of degrading exogenous fatty acids. These data bring to light a second exogenous fatty acid utilization pathway, expanding our knowledge on how this pathogen metabolizes environmental fatty acids.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0060926"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723290","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>Plasmodium falciparum</i> hemozoin-associated biomolecules induce brain endothelial cell barrier disruption in an <i>in vitro</i> model of cerebral malaria.","authors":"Kelly A Crotty, Ioana Clotea, Beatrix Ueberheide, Michael Cammer, Joseph Sall, Alice Liang, Ana Rodriguez","doi":"10.1128/mbio.00313-26","DOIUrl":"10.1128/mbio.00313-26","url":null,"abstract":"<p><p>Cerebral malaria is a major complication of <i>Plasmodium falciparum</i> infection that occurs upon the sequestration of infected red blood cells (iRBCs) in brain capillaries, resulting in the loss of endothelial barrier integrity, brain swelling, and frequently long-term sequelae or death. <i>P. falciparum</i>-iRBCs cause the disruption of human brain microvascular endothelial cell barrier integrity <i>in vitro</i>, mimicking the microenvironment of cerebral malaria, yet the specific mechanisms mediating this process remain unknown. Upon infection of the host RBCs, <i>P. falciparum</i> produces hemozoin, a crystal form of heme generated following the degradation of hemoglobin by the parasite. Here, we show that the endothelial barrier-disrupting activity is found entirely in the hemozoin fraction of <i>P. falciparum</i>-iRBCs. This activity is not caused by the hemozoin crystal itself, which is not able to induce barrier disruption, but by the biomolecules that are associated with it. Treatment of purified <i>P. falciparum</i> hemozoin with proteases inhibits the disruption of endothelial barrier integrity caused by the hemozoin, indicating an important role for proteins in the disruption of the barrier. Conversely, treatment with nucleases did not affect hemozoin barrier-disrupting activity. These results identify a key molecular mechanism in the <i>P. falciparum</i>-mediated brain endothelial barrier disruption during cerebral malaria and may open new avenues for the treatment of this complication.IMPORTANCEWhile several specific biomolecules have been proposed to contribute to the disruption of endothelial barrier integrity in cerebral malaria, no single <i>Plasmodium falciparum-</i> or host-derived factor has been definitively identified as the primary driver of this disruption. Here, we identify the brain endothelial barrier-disruptive <i>P. falciparum</i>-infected red blood cell (iRBC)-derived activity to be caused by biomolecules bound to hemozoin, identifying a key, novel mechanism in the pathogenesis of cerebral malaria. The finding that <i>P. falciparum</i> hemozoin also disrupts a pulmonary endothelial cell barrier opens the possibility that this mechanism underlies other severe malaria complications. The implication of <i>P. falciparum-</i>iRBC-derived proteins in this mechanism is in line with previous reports, providing a novel interpretation of these findings in the context of hemozoin-binding. This knowledge provides a new perspective in the search for specific molecules and mechanisms involved in barrier disruption, which may lead to the development of much-needed specific treatments for cerebral malaria.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0031326"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723327","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":"A beneficial endornavirus enhances the fitness of the phytopathogenic fungus <i>Rhizotonia solani</i>.","authors":"Tianxing Pang, Bokang Li, Qianqian Sun, Zhiping Deng, Chunmei Cao, Zhensheng Kang, Ida Bagus Andika, Liying Sun","doi":"10.1128/mbio.00166-26","DOIUrl":"10.1128/mbio.00166-26","url":null,"abstract":"<p><p>Although viruses are primarily characterized as pathogenic agents, certain viruses confer advantages to their hosts. The extent to which a virus can improve host biological performance, however, remains a fascinating topic in virology. An endornavirus, Rhizoctonia solani endornavirus IM (RsEV-IM), was identified as prevalent in <i>Rhizoctonia solani</i> isolates obtained from potato plants. Comparative analysis with a virus-free isogenic strain demonstrated that RsEV-IM infection enhances mycelial growth, sclerotium formation, stress tolerance, and fungal virulence across multiple plant species. Inoculation tests involving numerous <i>R. solani</i> strains confirmed that only RsEV-IM-infected strains exhibited high pathogenicity, independent of other mycovirus infections. Additionally, the secreted protein fraction of RsEV-IM-infected fungus contained elevated levels of various proteins, including those involved in cell wall degradation. This fraction not only facilitated <i>R. solani</i> infection but also suppressed the growth of other fungi and bacteria. These findings position RsEV-IM as a beneficial virus that widely enhances its host's biological fitness. From both pathological and ecological perspectives, these observations are significant, as they reveal that a mycovirus can serve as a key virulence determinant in fungal populations and potentially shape microbial community dynamics in natural environments.IMPORTANCEFungal pathogenicity and ecological traits have long been thought to be primarily governed by endogenous genetic factors. However, this study reveals a mutualistic relationship between an endornavirus (RsEV-IM) and <i>Rhizoctonia solani</i>, demonstrating that viral infection enhances fungal virulence and ecological fitness. RsEV-IM stimulates fungal growth and the secretion of cell wall-degrading enzymes, resulting in a severe disease phenotype. Ecologically, RsEV-IM-infected fungi potentially gain a competitive advantage over soil microbiota. These findings present a key example of a virus acting as an essential extrachromosomal determinant of fungal pathogenicity and ecosystem interactions. Our results advance the understanding of fungal virulence mechanisms and underscore the broader significance of beneficial virus-fungus associations in agriculture and microbial ecology.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0016626"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723356","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":"Inhibitors of cytochrome <i>c</i> biogenesis pathways.","authors":"Deanna L Mendez, Pema L Childs, Amidala J Martinie, Jonathan Q Huynh, Andy F Zhu, Samuel R McKee, George S Ghabrial, Christina L Stallings, Robert G Kranz","doi":"10.1128/mbio.00273-26","DOIUrl":"https://doi.org/10.1128/mbio.00273-26","url":null,"abstract":"<p><p>The unique composition of bacterial electron transport chains (ETCs), distinct from the human mitochondrial ETC, presents opportunities for selective antibacterial targeting. Recently, inhibitors of bacterial ETCs have shown promise as potential antimicrobials, particularly against mycobacteria. Notably, bacterial cytochrome c (cyt <i>c</i>) biogenesis systems-Systems I and II-are absent in mammalian mitochondria, which utilize System III. This divergence suggests that cyt <i>c</i> biosynthesis pathways may serve as novel antibiotic targets. In this study, we screened a library of 1,760 FDA-approved compounds for inhibitors of <i>in vivo</i> bacterial cyt <i>c</i> biogenesis. We identified seven compounds that inhibit either System I and/or System II pathways. Among these, artemisinin and its analogs (ARTs) were found to directly inhibit <i>in vitro</i> cyt <i>c</i> biogenesis using purified CcsBA (System II) and human HCCS (System III). ARTs disrupt heme at the active sites of cyt <i>c</i> synthases, indicating their potential as direct inhibitors. However, therapeutic use of ARTs would likely require co-administration with inhibitors targeting alternative bacterial respiratory chains that do not involve cyt <i>c</i>. Additionally, three members of the 8-hydroxyquinoline (8-HQ) class-clioquinol, chloroxine, and broxyquinoline-inhibited <i>in vivo</i> cyt <i>c</i> biogenesis at low micromolar concentrations, below those needed to suppress bacterial growth. Results suggest that 8-HQs act through mechanisms beyond simple metal chelation (e.g., iron, magnesium), likely targeting multiple bacterial processes. Consistent with this hypothesis, 8-HQs did not directly inhibit <i>in vitro</i> cyt <i>c</i> synthases.IMPORTANCEThis manuscript establishes bacterial cytochrome c biogenesis as a viable and previously underexplored antibacterial target that is fundamentally distinct from human mitochondrial pathways. Through systematic screening of 1,760 FDA-approved compounds, the study identifies two chemically and mechanistically distinct inhibitor classes-artemisinins and 8-hydroxyquinolines-that disrupt cytochrome c maturation via Systems I and II. The work moves beyond phenotypic growth inhibition by directly linking compound activity to heme degradation using complementary <i>in vivo</i> assays and <i>in vitro</i> experiments with purified cytochrome c synthases. Demonstrating that artemisinins directly target heme within these enzymes provides mechanistic insight with broad relevance to bacterial bioenergetics and drug-heme interactions. Importantly, the manuscript highlights the metabolic flexibility of bacterial respiratory chains and shows that inhibition of cytochrome c biogenesis alone is insufficient for robust killing. Together, these findings argue that cytochrome c biogenesis inhibitors will be effective in combination therapies and advance understanding of bacterial respiration.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0027326"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723298","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":"Innate immune responses to <i>Borrelia burgdorferi</i> during tick-feeding: mechanistic insights relevant to Lyme disease.","authors":"Suman Kundu, Greg Joyner, Maria Gomes-Solecki","doi":"10.1128/mbio.03971-25","DOIUrl":"10.1128/mbio.03971-25","url":null,"abstract":"<p><p>Immune responses to tick-transmitted <i>Borrelia burgdorferi</i> (Bb) have not been characterized <i>in vivo</i>. We analyzed the reservoir host's local and systemic immune responses to Bb during tick feeding. C3H/HeN mice were challenged via infected or uninfected nymphal <i>Ixodes scapularis</i> ticks or by subcutaneous injection of cultured multi-strain Bb. Skin and spleen tissues were evaluated by flow cytometry, serum was evaluated by cytokine proteome array, and all data were analyzed by comparison between each of the three challenged groups against the subcutaneously inoculated PBS control. Flow cytometry profiling shows that neutrophils, Langerhans cells, macrophages, B cells, and Natural Killer cells were mobilized in the three challenged groups in the skin and spleen, dendritic cells were increased in tick-transmitted groups, and T cells were engaged in Bb-challenged groups. Regarding soluble chemotaxis mediators in blood, all chemokines and cytokines induced by subcutaneously delivered Bb and uninfected tick were also induced by tick-transmitted Bb. However, tick-transmitted Bb induced unique factors absent in the other groups, which included chemokines involved in recruitment of phagocytic cells and T cell engagement, and cytokines associated with broader T cell activation. Regarding anti-inflammatory mediators, although IL-1ra was increased in the three challenged groups, IL-10 was only increased in tick-challenged groups with or without Bb. The data suggest that tick-transmitted Bb induced much more dynamic but regulated immune responses during tick-feeding, compared to subcutaneously delivered Bb, which may explain Bb persistence in the reservoir host.IMPORTANCECurrent knowledge on immune cell interactions with <i>Borrelia burgdorferi</i> (Bb) derives mostly from studies done <i>in vitro</i> and <i>ex vivo,</i> which cannot assess host immunity to natural tick-delivered Bb within the complex architecture of host tissues. We report the first <i>in vivo</i> study on local and systemic immune responses to Bb during tick feeding on a surrogate reservoir host, in comparison with uninfected-tick and subcutaneously delivered Bb. We show that uninfected-tick and tick-transmitted Bb engaged mixed type-1/type-2/type-17 immune responses in the presence of anti-inflammatory IL-10, in contrast to a type-1 response induced by subcutaneously delivered Bb. Analyses of immune responses to tick-transmitted Bb in a reservoir host can enlighten immunity mechanisms that mediate persistence of Bb.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0397125"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723316","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":"Facultative predation expands the ecological repertoire of <i>Streptomyces</i>.","authors":"Keith Yamada, Arina Koroleva, Heli Tirkkonen, Vilja Siitonen, Mitchell Laughlin, Amanda Moglia, Soheila Matroodi, Amir Akhgari, Guillaume Mazurier, Jarmo Niemi, Mikko Metsä-Ketelä","doi":"10.1128/mbio.00563-26","DOIUrl":"https://doi.org/10.1128/mbio.00563-26","url":null,"abstract":"<p><p>Microbial predators obtain energy from killing other living cells. <i>Streptomyces</i> are soil bacteria that are known to produce numerous catabolic enzymes and antimicrobial compounds to defend against competing organisms. Here, we demonstrate that <i>Streptomyces</i> are predatory bacteria that prey on <i>Saccharomyces cerevisiae</i>. Time-lapse fluorescence microscopy and scanning electron microscopy revealed that predation is initiated by physical contact between <i>Streptomyces lavendulae</i> YAKB-15 and yeast cells. Comparative transcriptomics indicated that the interaction triggered the production of numerous extracellular catabolic enzymes and natural products, while delaying morphological development. Proteomics and enzyme assays confirmed co-culture-dependent production of carbohydrate-active enzymes (CAZymes), including various glucanases, mannosidases, and chitinases, which degraded the yeast cell wall. <i>Streptomyces lavendulae</i> YAKB-15 destabilized yeast cell membranes through the production of two polyene antifungal agents, pentamycin and filipin III. We found that the bioactivity was enhanced by cell-associated cholesterol oxidase ChoD, putatively by modulating sterol extraction kinetics. Metabolomic analyses suggest <i>Streptomyces</i> assimilates yeast cell sterols as nutrients. Furthermore, we observed the depletion of yeast-derived phosphatidylcholine and phosphatidylethanolamine lipids, which points to their consumption. We show that yeast predation is a common phenomenon in <i>Streptomyces</i>, which changes the paradigm of how these bacteria should be considered in the soil microbiome ecosystem.IMPORTANCESoil is a rich environment for microbes, where they compete for space and resources. <i>Streptomyces</i> bacteria are well known for their ability to synthesize natural products, particularly antibiotics, that are used in chemical defense against competing microbes. Here, we show that <i>Streptomyces</i> are, in fact, predatory bacteria. Upon encountering yeast cells, <i>Streptomyces</i> initiate the production of numerous enzymes that digest the cell wall and cell membrane. In addition, the interaction triggers the production of natural products that destabilize the yeast cell membrane. Collectively, these actions lead to the death of yeast cells and release of cellular building blocks that <i>Streptomyces</i> can use as nutrients. The work fundamentally shifts the paradigm of how <i>Streptomyces</i> are perceived within the soil microbiome ecosystem.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0056326"},"PeriodicalIF":4.7,"publicationDate":"2026-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723348","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}