mBio最新文献

{"title":"Infection-relevant conditions dictate differential versus coordinate expression of <i>Salmonella</i> chaperones and cochaperones.","authors":"Carissa Chan, Keiichiro Mukai, Eduardo A Groisman","doi":"10.1128/mbio.00227-25","DOIUrl":"10.1128/mbio.00227-25","url":null,"abstract":"<p><p>Molecular chaperones are critical for protein homeostasis. In bacteria, chaperone trigger factor (TF) folds proteins co-translationally, and chaperone DnaK requires a J-domain cochaperone and nucleotide exchange factor GrpE to fold proteins largely post-translationally. However, when the pathogen <i>Salmonella enterica</i> serovar Typhimurium faces the infection-relevant condition of cytoplasmic Mg²⁺ starvation, DnaK reduces protein synthesis independently. This raises the possibility that bacteria differentially express chaperones and cochaperones. We now report that <i>S</i>. Typhimurium responds to cytoplasmic Mg²⁺ starvation by increasing mRNA amounts of <i>dnaK</i> while decreasing those of the TF-encoding gene <i>tig</i> and J-domain cochaperone genes <i>dnaJ</i> and <i>djlA</i>. This differential strategy requires the master regulator of Mg²⁺ homeostasis and virulence PhoP, which increases <i>dnaK</i> mRNA amounts by lowering the ATP concentration, thereby hindering proteolysis of the alternative sigma factor RpoH responsible for <i>dnaK</i> transcription. We also establish that DnaK exerts negative feedback on the RpoH protein and RpoH-dependent transcripts independently of J-domain cochaperones. Thus, bacteria express chaperones and cochaperones coordinately or differentially depending on the specific stress perturbing protein homeostasis.IMPORTANCEMolecular chaperones typically require cochaperones to fold proteins and to prevent protein aggregation, and the corresponding genes are thus coordinately expressed. We have now identified an infection-relevant stress condition in which the genes specifying chaperone DnaK and cochaperone DnaJ are differentially expressed despite belonging to the same operon. This differential strategy requires the master regulator of Mg²⁺ homeostasis and virulence in the pathogen <i>Salmonella enterica</i> serovar Typhimurium. Moreover, it likely reflects that <i>Salmonella</i> requires <i>dnaK</i>, but not J-domain cochaperone-encoding genes, for survival against cytoplasmic Mg²⁺ starvation and expresses genes only when needed. Thus, the specific condition impacting protein homeostasis determines the coordinate versus differential expression of molecular chaperones and cochaperones.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0022725"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077118/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143753048","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":"Snow algae exhibit diverse motile behaviors and thermal responses.","authors":"Alexandre Détain, Hirono Suzuki, René H Wijffels, Nathalie Leborgne-Castel, Chris J Hulatt","doi":"10.1128/mbio.02954-24","DOIUrl":"10.1128/mbio.02954-24","url":null,"abstract":"<p><p>Snow algal blooms influence snow and glacier melt dynamics, yet the mechanisms involved in community assemblage, development, and dispersal are not well understood. While microbial swimming behavior contributes significantly to the productivity and organization of aquatic and terrestrial microbiomes, the potential impact of algal cell motility in melting snow on the formation of visible, large-scale surface bloom patterns is largely unknown. Here, using video tracking and phototaxis experiments of unique isolates, we evaluated the motility of diverse snow algal taxa from green, red, and golden colored snow blooms in response to light and thermal gradients. We show that many species are efficient cryophilic microswimmers with speed thermal optima below 10°C although taxa with cryotolerant swimming traits were also identified. The significant motility of snow algae at low temperatures, a result of specialized adaptations, supports the importance of active movement in the life histories of algae inhabiting snow meltwater. However, diversity in swimming performance and behavior reveal a range of evolutionary outcomes and sensitivity of motile life stages to dynamic environments.IMPORTANCESwimming motility is a fundamental mechanism that controls the assembly, structure, and productivity of microbiomes across diverse environments and is highly sensitive to temperature. Especially, the role of cell swimming activity in algal bloom formation at the very low temperatures of snowmelt has been hypothesized, but not studied. By examining the movement patterns of snow algae and modeling the thermal response curves of swimming speed, the data reveal the key role of active cell movement that may have further important impacts on the microbial ecology and melt rates of snow and ice in polar and alpine regions.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0295424"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077220/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143753338","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 PqsE as a <i>Pseudomonas aeruginosa</i>-specific regulator of LuxR-type receptors: insights from <i>Pseudomonas</i> and <i>Burkholderia</i>.","authors":"Caleb P Mallery, Kayla A Simanek, Autumn N Pope, Jon E Paczkowski","doi":"10.1128/mbio.00646-25","DOIUrl":"10.1128/mbio.00646-25","url":null,"abstract":"<p><p><i>Pseudomonas aeruginosa</i> is a Gram-negative opportunistic pathogen that poses a significant public health threat, particularly in healthcare settings. A key determinant of <i>P. aeruginosa</i> virulence is the regulated synthesis and release of extracellular products, which is controlled by a cell density-dependent signaling system known as quorum sensing (QS). <i>P. aeruginosa</i> uses a complex QS network, including two systems that rely on diffusible N-acylhomoserine lactone (AHL) signal molecules. The LuxR-type receptor RhlR is unique in that it requires not only its cognate AHL but also the accessory protein PqsE to maximally bind to promoter DNA and initiate transcription. Our group previously demonstrated that PqsE physically interacts with RhlR, enhancing its affinity for target promoters across the <i>P. aeruginosa</i> genome. Although LuxR-type receptors are widespread in Gram-negative bacteria and important for pathogenesis, PqsE orthologs are restricted to <i>Pseudomonas</i> and <i>Burkholderia</i> species. This study explored the conservation of PqsE and examined PqsE ortholog structure-function across different species. Our results show that PqsE in <i>Pseudomonas</i> retains their functional interactions with RhlR homologs, unlike PqsE orthologs in <i>Burkholderia</i> spp., which do not interact with their respective LuxR-type receptors. Additionally, we assessed the AHL preferences of different receptors and hypothesized that the PqsE-RhlR interaction evolved to stabilize the inherently unstable RhlR, preventing its degradation. Indeed, we observe higher levels of RhlR protein turnover in a strain lacking <i>pqsE</i> compared to a wild-type strain of PA14, which can be partially rescued in a strain of <i>P. aeruginosa</i> lacking the Lon protease.</p><p><strong>Importance: </strong><i>Pseudomonas aeruginosa</i>, a major pathogen for patients with cystic fibrosis and a primary constituent of healthcare-associated infections, relies on a complex quorum-sensing (QS) network to coordinate virulence factor production. Central to this system is the interaction between two proteins, PqsE and RhlR, which drive gene expression essential for pathogenesis. Our study investigates the conservation of the PqsE-RhlR interaction across related bacterial species, revealing that PqsE in <i>Pseudomonas</i> can enhance RhlR activity, while orthologs in <i>Burkholderia</i> lack this capacity. These findings offer new insights into the specificity and evolution of QS mechanisms, highlighting the PqsE-RhlR interaction as a potentially selective target for treating <i>P. aeruginosa</i> infections.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0064625"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077149/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143803490","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":"Larval zebrafish burn wound infection model reveals conserved innate immune responses against diverse pathogenic fungi.","authors":"Nayanna M Mercado Soto, Adam Horn, Nancy P Keller, Anna Huttenlocher, Andrew S Wagner","doi":"10.1128/mbio.03480-24","DOIUrl":"10.1128/mbio.03480-24","url":null,"abstract":"<p><p>Secondary fungal infections represent a major complication following thermal injuries. However, the mechanisms of fungal colonization of burn tissue and how the host subsequently responds to fungi within this niche remain unclear. We have previously reported a zebrafish model of thermal injury that recapitulates many of the features of human burn wounds. Here, we characterize host-fungal interaction dynamics within the burn wound niche using two of the most common fungal pathogens isolated from burn injuries, <i>Aspergillus fumigatus</i> and <i>Candida albicans</i>. Both <i>A. fumigatus</i> and <i>C. albicans</i> colonize burned tissue in zebrafish larvae and induce a largely conserved innate immune response following colonization. Using drug-induced cell-depletion strategies and transgenic zebrafish lines with impaired innate immune function, we found that macrophages control fungal burden, whereas neutrophils primarily control invasive hyphal growth at the early stages of infection. However, we also found that loss of either immune cell can be compensated by the other at the later stages of infection and that fish with both macrophage and neutrophil deficiencies show more invasive hyphal growth that is sustained throughout the infection process, suggesting redundancy in their antifungal activities. Finally, we demonstrate that <i>C. albicans</i> strains with increased β(1,3)-glucan exposure are cleared faster from the burn wound, demonstrating a need for shielding this immunogenic cell wall epitope for the successful fungal colonization of burn tissue. Together, our findings support the use of zebrafish larvae as a model to study host-fungal interaction dynamics within burn wounds.IMPORTANCESecondary fungal infections within burn wound injuries are a significant problem that delays wound healing and increases the risk of patient mortality. Currently, little is known about how fungi colonize and infect burn tissue or how the host responds to pathogen presence. In this report, we expand upon an existing thermal injury model using zebrafish larvae to begin elucidating both the host immune response to fungal burn colonization and fungal mechanisms for persistence within burn tissue. We found that both <i>Aspergillus fumigatus</i> and <i>Candida albicans</i>, common fungal burn wound isolates, successfully colonize burn tissue and are effectively cleared in immunocompetent zebrafish by both macrophages and neutrophils. We also find that <i>C. albicans</i> mutants harboring mutations that impact their ability to evade host immune system recognition are cleared more readily from burn tissue. Collectively, our work highlights the efficacy of using zebrafish to study host-fungal interaction dynamics within burn wounds.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0348024"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077223/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143803498","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":"The juxtamembrane domain of StkP is phosphorylated and influences cell division in <i>Streptococcus pneumoniae</i>.","authors":"Mélisse Hamidi, Sathya Narayanan Nagarajan, Vaishnavi Ravikumar, Virginie Gueguen-Chaignon, Cédric Laguri, Céline Freton, Ivan Mijakovic, Jean-Pierre Simorre, Stéphanie Ravaud, Christophe Grangeasse","doi":"10.1128/mbio.03799-24","DOIUrl":"10.1128/mbio.03799-24","url":null,"abstract":"<p><p>Eukaryotic-like membrane Ser/Thr protein kinases play a pivotal role in different aspects of bacterial physiology. In contrast to the diversity of their extracellular domains, their cytoplasmic catalytic domains are highly conserved. However, the function of a long juxtamembrane domain (JMD), which connects the catalytic domain to the transmembrane helix, remains elusive. In this study, we investigated the function of the JMD of the Ser/Thr protein kinase StkP in the cell division of <i>Streptococcus pneumoniae</i>. We observed that the deletion of the JMD affected the ability of StkP to phosphorylate some of its endogenous substrates, thereby resulting in significant cell morphogenesis defects. Furthermore, multiple threonine residues were identified as being phosphorylated in the JMD. To investigate the functional significance of these phosphorylation sites, we conducted an integrative analysis, combining structural biology, proteomics, and bacterial cell imaging. Our results revealed that the phosphorylation of the JMD did not perturb the phosphorylation of StkP substrates. However, we observed that it modulated the timing of StkP localization to the division septum and the dynamics of cell constriction. We further demonstrated that phosphorylation of the JMD facilitated the recruitment of several cell division proteins, suggesting that it is required to assemble the division machinery at the division septum. In conclusion, this study demonstrates that the function of the JMD of StkP is modulated by phosphorylation and is critical for the cell division of <i>S. pneumoniae</i>. These observations may serve as a model for understanding the regulatory function of other bacterial Ser/Thr protein kinases.IMPORTANCEHow bacterial serine/threonine protein kinases are activated remains highly debated. In particular, models rely on the observations made with their eukaryotic counterparts, and only a few studies have investigated the molecular activation mechanism of bacterial serine/threonine protein kinases. This is particularly the case with regard to the juxtamembrane domain (JMD), which is proposed to contribute to kinase activation in numerous eukaryotic kinases. This study demonstrates that the juxtamembrane domain is likely not essential for the activation of the serine/threonine protein kinase StkP of <i>S. pneumoniae</i>. Rather, our findings reveal that it is required for cell division, where its phosphorylation affects the assembly of the division machinery at the division septum. These observations allow us to assign a function to the JMD in StkP-mediated regulation of pneumococcal cell division, thereby providing a new avenue for understanding the contribution of membrane serine/threonine protein kinases in the physiology of other bacteria.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0379924"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077195/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143803517","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":"Selective expression of <i>Pneumocystis</i> antigens in different patients during a suspected outbreak of <i>Pneumocystis</i> pneumonia.","authors":"Caroline S Meier, Marco Pagni, Sophie Richard, Konrad Mühlethaler, Philippe M Hauser","doi":"10.1128/mbio.00692-25","DOIUrl":"10.1128/mbio.00692-25","url":null,"abstract":"<p><p>The fungus <i>Pneumocystis jirovecii</i> causes severe pneumonia in immunocompromised individuals. It harbors a system of surface antigenic variation involving six families of major surface glycoproteins (Msg). We determined the repertoires of <i>P. jirovecii msg</i> genes of the most abundant family-I present in 15 Swiss patients with <i>Pneumocystis</i> pneumonia (PCP) enrolled randomly. The highly repetitive <i>msg</i>-I genes were sequenced using generic PCRs followed by circular consensus sequencing with long reads. In contrast to the other 12 patients, three renal transplant recipients (RTRs) harbored the same repertoire of <i>msg</i>-I genes. Multilocus genotyping showed that these RTRs were infected by the same <i>P. jirovecii</i> genotype that differed from those present in the other 12 patients. These observations suggested that these RTRs were involved in an outbreak of PCP due to interhuman transmission or a common source of the fungus. Although they harbored the same repertoire of <i>msg</i>-I genes, the sets of <i>msg</i>-I genes that were expressed differed between the three patients. This suggested that selective expression of <i>P. jirovecii</i> surface antigens might have played a role in the pathogenesis of PCP by allowing escape from the immune response specific to each patient. Although expected for a family of genes, this is the first time that selective expression of antigens is observed in <i>Pneumocystis</i>. The previously described adaptation of <i>P. jirovecii</i> to infect solid organ transplant (SOT) recipients through resistance to the immunosuppressant mycophenolate probably also favored the suspected outbreak. Moreover, our study supports the idea that various <i>P. jirovecii</i> genotypes can adapt to infect SOT recipients.IMPORTANCEThe fungus <i>Pneumocystis</i> causes severe pneumonia in patients with weakened immune systems. It possesses a genetic system to vary the antigens at the surface of its cells that are presented to the immune system of the patient. We report for the first time that this system may have been implicated in the infections of renal transplant recipients involved in a suspected outbreak. Our observations suggest that the antigens presented might be selected to avoid the elimination of the fungus by the immune response specific to each patient. The resistance of the fungus to the immunosuppressant mycophenolate administered to these patients to prevent organ rejection probably also played a role in the infections during the suspected outbreak.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":"16 5","pages":"e0069225"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077189/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144017364","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":"Microbes as manipulators of egg size and developmental evolution.","authors":"Matthew C Kustra, Tyler J Carrier","doi":"10.1128/mbio.03655-24","DOIUrl":"10.1128/mbio.03655-24","url":null,"abstract":"<p><p>Marine invertebrates mainly reproduce by energy-poor eggs that develop into feeding larvae or energy-rich eggs that develop into non-feeding larvae. Evolutionary transitions between these developmental modes have been studied in detail, yet the evolutionary factor(s) responsible for these switches remains elusive. Here, we use theoretical models to support the premise that microbes with the capacity to manipulate host reproduction may be one possible factor. Our model predicts that microbial manipulators could create a sperm-limited environment that selects for larger eggs by shifting the host's sex ratio toward female dominance and, as a result, drive an evolutionary transition in the developmental mode for marine invertebrates. The loss of a microbial manipulator could then recover the ancestral egg size and developmental mode. We also suggest more than a dozen genera of marine invertebrates from throughout the world's oceans that fit the framework of a microbe-induced evolutionary transition between these predominant developmental modes. We anticipate that microbial manipulators have a yet-to-be-appreciated influence on the developmental evolution of marine invertebrates. We find it paramount to understand whether evolutionary transitions in developmental mode occur with and without microbial manipulators as well as whether the underlying mechanisms of these manipulations are convergent with terrestrial systems.</p><p><strong>Importance: </strong>Microbes that manipulate animal reproduction are widespread on land, and their evolutionary influence is widely acknowledged. Relatives of these manipulators are increasingly found in the ocean, but uniquely with taxa that recently underwent a transition in developmental evolution from feeding to non-feeding larvae. Here, we present theoretical models supporting that microbial manipulators could create a sperm-limited environment that selects for larger eggs by shifting the host's sex ratio toward female dominance and, as a result, drive an evolutionary transition in the developmental mode for free-spawning marine invertebrates. This theoretical model provides a complementary viewpoint to the theory regarding the evolutionary process that marine invertebrates undergo to transition between developmental modes as well as a fruitful opportunity to compare with terrestrial systems.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":"16 5","pages":"e0365524"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077187/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144017796","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":"The same but different: impact of animal facility sanitary status on a transgenic mouse model of Alzheimer's disease.","authors":"Caroline Ismeurt-Walmsley, Patrizia Giannoni, Florence Servant, Linda-Nora Mekki, Kevin Baranger, Santiago Rivera, Philippe Marin, Benjamin Lelouvier, Sylvie Claeysen","doi":"10.1128/mbio.04001-24","DOIUrl":"10.1128/mbio.04001-24","url":null,"abstract":"<p><p>The gut-brain axis has emerged as a key player in the regulation of brain function and cognitive health. Gut microbiota dysbiosis has been observed in preclinical models of Alzheimer's disease and patients. Manipulating the composition of the gut microbiota enhances or delays neuropathology and cognitive deficits in mouse models. Accordingly, the health status of the animal facility may strongly influence these outcomes. In the present study, we longitudinally analyzed the fecal microbiota composition and amyloid pathology of 5XFAD mice housed in a specific opportunistic pathogen-free (SOPF) and a conventional facility. The composition of the microbiota of 5XFAD mice after aging in conventional facility showed marked differences compared to WT littermates that were not observed when the mice were bred in SOPF facility. The development of amyloid pathology was also enhanced by conventional housing. We then transplanted fecal microbiota (FMT) from both sources into wild-type (WT) mice and measured memory performance, assessed in the novel object recognition test, in transplanted animals. Mice transplanted with microbiota from conventionally bred 5XFAD mice showed impaired memory performance, whereas FMT from mice housed in SOPF facility did not induce memory deficits in transplanted mice. Finally, 18 weeks of housing SOPF-born animals in a conventional facility resulted in the reappearance of specific microbiota compositions in 5XFAD vs WT mice. In conclusion, these results show a strong impact of housing conditions on microbiota-associated phenotypes and question the relevance of breeding preclinical models in specific pathogen-free (SPF) facilities.</p><p><strong>Importance: </strong>Housing conditions affect the composition of the gut microbiota. Gut microbiota of 6-month-old conventionally bred Alzheimer's mice is dysbiotic. Gut dysbiosis is absent in Alzheimer's mice housed in highly sanitized facilities. Transfer of fecal microbiota from conventionally bred mice affects cognition. Microbiota of mice housed in highly sanitized facilities has no effect on cognition.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":"16 5","pages":"e0400124"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077201/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144064105","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":"Analysis of genetic requirements and nutrient availability for <i>Staphylococcus aureus</i> growth in cystic fibrosis sputum.","authors":"Lauren M Shull, Daniel J Wolter, Dillon E Kunkle, Katherine A Legg, David P Giedroc, Eric P Skaar, Lucas R Hoffman, Michelle L Reniere","doi":"10.1128/mbio.00374-25","DOIUrl":"10.1128/mbio.00374-25","url":null,"abstract":"<p><p><i>Staphylococcus aureus</i> is one of the most common pathogens isolated from the lungs of people with cystic fibrosis (CF), but little is known about its ability to colonize this niche. We performed a transposon-sequencing (Tn-seq) screen to identify genes necessary for <i>S. aureus</i> growth in media prepared from <i>ex vivo</i> CF sputum. We identified 19 genes that were required for growth in all sputum media tested and dozens more that were required for growth in at least one sputum medium. Depleted mutants of interest included insertions in many genes important for surviving metal starvation, as well as the primary regulator of cysteine metabolism, <i>cymR</i>. To investigate the mechanisms by which these genes contribute to <i>S. aureus</i> growth in sputum, we quantified low-molecular-weight thiols, nutrient transition metals, and the host metal-sequestration protein calprotectin in sputum from 11 individuals with CF. In all samples, the abundance of calprotectin exceeded nutrient metal concentration, explaining the <i>S. aureus</i> requirement for metal-starvation genes. Furthermore, all samples contain potentially toxic quantities of cysteine and sufficient glutathione to satisfy the organic sulfur requirements of <i>S. aureus</i>. Deletion of the cysteine importer genes <i>tcyA</i> and <i>tcyP</i> in the ∆<i>cymR</i> background restored growth to wild-type levels in CF sputum, suggesting that the mechanism by which <i>cymR</i> is required for growth in sputum is to prevent uncontrolled import of cysteine or cystine from this environment. Overall, this work demonstrates that calprotectin and cysteine limit <i>S. aureus</i> growth in CF sputum.IMPORTANCE<i>Staphylococcus aureus</i> is a major cause of lung infections in people with cystic fibrosis (CF). This work identifies genes required for <i>S. aureus</i> growth in this niche, which represent potential targets for anti-Staphylococcal treatments. We show that genes involved in surviving metal starvation are required for growth in CF sputum. We also found that the primary regulator of cysteine metabolism, CymR, plays a critical role in preventing cysteine intoxication during growth in CF sputum. To support these models, we analyzed sputum from 11 individuals with CF to determine concentrations of calprotectin, nutrient metals, and low-molecular-weight thiols, which have not previously been quantified together in the same samples.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0037425"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077221/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143764271","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":"Forward genetic screen in zebrafish identifies new fungal regulators that limit host-protective <i>Candida</i>-innate immune interaction.","authors":"Bailey A Blair, Emma Bragdon, Gursimran Dhillon, Nnamdi Baker, Lena Stasiak, Mya Muthig, Pedro Miramon, Michael C Lorenz, Robert T Wheeler","doi":"10.1128/mbio.00529-25","DOIUrl":"10.1128/mbio.00529-25","url":null,"abstract":"<p><p><i>Candida</i> is one of the most frequent causes of bloodstream infections, and our first line of defense against these invasive infections is the innate immune system. The early immune response is critical in controlling <i>Candida albicans</i> infection, but <i>C. albicans</i> has several strategies to evade host immune attack. Phagocytosis of <i>C. albicans</i> blocks hyphal growth, limiting host damage and virulence, but how <i>C. albicans</i> limits early recruitment and phagocytosis in vertebrate infection is poorly understood. To study innate immune evasion by intravital imaging, we utilized the transparent larval zebrafish infection model to screen 131 <i>C</i>. <i>albicans</i> mutants for altered virulence and phagocyte response. Infections with each of the seven hypovirulent mutants led to altered phagocyte recruitment and/or phagocytosis, falling into four categories. Of particular interest among these is <i>NMD5</i>, a predicted β-importin and newly identified virulence factor. The <i>nmd5</i>∆/∆ mutant fails to limit phagocytosis, and its virulence defects are eliminated when phagocyte activity is compromised, suggesting that its role in virulence is limited to immune evasion. These quantitative intravital imaging experiments are the first to document altered <i>Candida</i>-phagocyte interactions for several additional mutants and clearly distinguish recruitment from phagocytic uptake, suggesting that <i>Candida</i> modulates both events. This initial large-scale screen of individual <i>C. albicans</i> mutants in a vertebrate, coupled with high-resolution imaging of <i>Candida</i>-phagocyte interactions, provides a more nuanced view of how diverse mutations can lead to more effective phagocytosis, a key immune process that blocks germination and drives anti-fungal immunity.</p><p><strong>Importance: </strong><i>Candida albicans</i> is part of the human microbial community and is a dangerous opportunistic pathogen, able to prevent its elimination by the host immune system. Although <i>Candida</i> avoids immune attack through several strategies, we still understand little about how it regulates when immune phagocytes get recruited to the infection site and when they engulf fungal cells. We tested over 130 selected <i>Candida</i> mutants for their ability to cause lethal infection and found several hypovirulent mutants, which provoked altered innate immune responses, resulting in lower overall inflammation and greater host survival. Of particular interest is <i>NMD5</i>, which acts to limit fungal phagocytosis and is predicted to regulate the activity of stress-associated transcription factors. Our high-content screening was enabled by modeling <i>Candida</i> infection in transparent vertebrate zebrafish larva. Our findings help us understand how <i>Candida</i> survives immune attack during commensal and pathogenic growth, and may eventually inform new strategies for controlling disease.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0052925"},"PeriodicalIF":5.1,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12077120/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143764274","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}