mSphere最新文献

{"title":"Protein malnutrition facilitates intestinal colonization with highly resistant <i>Klebsiella pneumoniae</i> through disrupted intestinal microbial metabolism.","authors":"Thomas Holowka, Veronica Feijoli Santiago, Jamie Xiao, Mera F Liccione, Alisher Bimagambetov, Charles R Tucker, Kenneth Walsh, Shan Sun, Anthony A Fodor, Jason W Arnold, Kalisvar Marimuthu, Oon Tek Ng, Jonathan R Swann, David van Duin, Luther A Bartelt","doi":"10.1128/msphere.00321-26","DOIUrl":"https://doi.org/10.1128/msphere.00321-26","url":null,"abstract":"<p><p>Pediatric infections with highly resistant <i>Klebsiella pneumoniae</i> (HR-Kp) disproportionately affect low-income countries where childhood malnutrition is prevalent. Malnutrition is an identified risk factor for infection with HR-Kp and other antimicrobial-resistant Enterobacterales, but the mechanistic underpinnings of this link and independence from other common exposures, like antibiotics, in children are unclear. Using a murine model of pediatric malnutrition, we found that mice fed a protein-deficient diet (PD) were more susceptible to colonization with HR-Kp at a 4-log lower challenge inoculum and developed a 3-log higher intestinal burden in comparison to adequately nourished mice. HR-Kp colonization in PD-fed mice persisted beyond 5 weeks, and colonization was transmitted to diet-matched cage mates. Antibiotic treatment resulted in similar HR-Kp colonization burdens regardless of diet, suggesting that nutrition-dependent colonization risk is driven by altered intestinal microbiota. Despite reduced dietary protein intake, intestinal amino acid content was maintained in PD-fed mice, supporting optimal HR-Kp growth. Furthermore, secondary bile acids, prototypic intestinal microbiota-derived molecules, were reduced in PD-fed mice, demonstrated an inverse correlation with HR-Kp burden <i>in vivo</i>, and partially inhibited the growth of HR-Kp <i>in vitro</i>. Collectively, these findings reveal a role for dietary protein intake in determining nutrition-dependent colonization resistance to HR-Kp.IMPORTANCEAntimicrobial-resistant <i>Klebsiella pneumoniae</i> are responsible for a growing mortality burden worldwide, with disproportionate rates of infection in low-income countries where childhood malnutrition is prevalent. Several publications have demonstrated high rates of intestinal colonization with antimicrobial-resistant <i>K. pneumoniae</i> in children admitted with severe malnutrition in sub-Saharan Africa. However, numerous confounding risk factors in malnourished children (antibiotic use, healthcare exposure, and immune dysfunction) make it difficult to assess the direct impact of nutrition on <i>K. pneumoniae</i> colonization. In this study, we utilized a novel mouse model of protein malnutrition to demonstrate that dietary protein deficiency renders mice susceptible to a higher burden of intestinal colonization at a lower inoculating dose of <i>K. pneumoniae</i>. Furthermore, reduced microbiota-derived bile acid metabolites correlate with increased burden of colonization in protein-deficient mice. These results are the first to establish a direct mechanistic link associating dietary protein deficiency, bile acid metabolism, and intestinal colonization with antimicrobial-resistant <i>K. pneumoniae</i>.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0032126"},"PeriodicalIF":4.0,"publicationDate":"2026-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149220522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of the <i>Peromyscus leucopus</i> immunoglobulin germline repertoire and anti-OspA antibody response reveals conserved germline IGHV features among cricetid rodents.","authors":"Yu Zhou, Sam R Telford, Joanna Buchthal, Kevin Esvelt, William Lees, Corey T Watson, Yana Safonova, Wayne A Marasco","doi":"10.1128/msphere.00473-26","DOIUrl":"https://doi.org/10.1128/msphere.00473-26","url":null,"abstract":"<p><p><i>Peromyscus leucopus</i> (<i>P. leucopus</i>) is an important reservoir host for several zoonoses, including <i>Borrelia burgdorferi</i> (<i>B. burgdorferi</i>), the causative agent of Lyme disease. However, the immunoglobulin germline repertoire underlying antibody responses in this reservoir host remains poorly defined. In this study, we characterized the immunoglobulin variable genes of <i>P. leucopus</i> and identified 12 IGHV, 12 IGKV, and 3 IGLV gene families comprising 129, 87, and 12 genes, respectively. These genes exhibited similar usage patterns to those of <i>Mus musculus</i> (<i>M. musculus</i>). We also identified a high-divergence region (HDR) within the germline IGHV loci of three <i>Borrelia</i> sp.-susceptible Cricetidae species, <i>P. leucopus</i>, <i>Peromyscus maniculatus</i> (<i>P. maniculatus</i>), and <i>Arvicola amphibius</i> (<i>A. amphibius</i>). Compared with the corresponding regions in Muridae species, the Cricetidae HDRs are expanded and contain a large number of IGHV genes. To investigate the antigen-specific features of the repertoire, we analyzed the antibody responses of <i>P. leucopus</i> to <i>B. burgdorferi</i> outer surface protein A (OspA), a highly immunogenic tick midgut adhesin involved in midgut colonization. Comparative analysis of more than 140 IGHV genes from immunized <i>P. leucopus</i> showed that germline IGHV genes encoding anti-OspA antibodies exhibited higher sequence similarity to corresponding germline IGHV genes in <i>P. maniculatus</i> and <i>A. amphibius</i> than did <i>P. leucopus</i> germline IGHV genes not associated with anti-OspA responses.IMPORTANCEThis study characterized the immunoglobulin gene repertoire of <i>Peromyscus leucopus</i> and revealed extensive diversity across its variable-region loci. Analysis of antibody response to outer surface protein A (OspA) showed that germline IGHV genes encoding anti-OspA antibodies showed higher sequence similarity to their corresponding germline IGHV genes in other <i>Borrelia</i>-susceptible cricetid rodents, suggesting that conserved germline IGHV features are associated with OspA recognition. These findings lay the foundation for further understanding of antibody responses in this important reservoir host.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0047326"},"PeriodicalIF":4.0,"publicationDate":"2026-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149195665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Erratum for Bernier Gosselin et al., \"Associations of antimicrobial and multidrug resistance in <i>Escherichia coli</i> from the fecal flora and housing environment of calves on dairy farms with atmospheric variables\".","authors":"Véronique Bernier Gosselin, Martin Wegmann, Romane Zufferey, Vincent Perreten, Mireille Meylan","doi":"10.1128/msphere.00732-26","DOIUrl":"https://doi.org/10.1128/msphere.00732-26","url":null,"abstract":"","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0073226"},"PeriodicalIF":4.0,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149183154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"HIV-1 Tat protects macrophages from killing by the exoenzyme U from <i>Pseudomonas aeruginosa</i>.","authors":"Maxime Jansen, Aurélie Rivault, Angéline Tellier, Lise Chauveau, Anne Blanc-Potard, Bruno Beaumelle","doi":"10.1128/msphere.00674-26","DOIUrl":"https://doi.org/10.1128/msphere.00674-26","url":null,"abstract":"<p><p>People living with HIV (PLWH) have a higher risk of developing other diseases, such as bacterial pneumonia. <i>Pseudomonas aeruginosa</i> is a common cause of pneumonia in humans. The most virulent strains produce ExoU, which is a key effector of <i>P. aeruginosa</i> cytotoxicity. Upon injection into the target cell cytosol by the type III secretion system (T3SS), ExoU binds to PI(4,5)P₂ on the inner leaflet of the plasma membrane. ExoU phospholipase activity then induces a loss of plasma membrane integrity, rapidly leading to cell death. HIV-1-Tat is secreted by HIV-infected cells, leading to nanomolar concentrations of Tat in the sera of PLWH, even under antiretroviral therapy. Circulating Tat is endocytosed by uninfected cells, translocates to the cytosol, and binds to PI(4,5)P₂ at the plasma membrane. In uninfected cells only, Tat is palmitoylated, enabling Tat to become resident on PI(4,5)P₂. Here, we found that Tat interferes with the recruitment of ExoU by PI(4,5)P₂, thereby protecting primary human macrophages from the toxicity of <i>exoU</i>-positive <i>P. aeruginosa</i> strains. Tat nevertheless enhances the toxicity of <i>exoU</i>-deficient strains of <i>P. aeruginosa</i> toward macrophages. HIV Tat might, therefore, modulate the sensitivity of PLWH toward <i>P. aeruginosa</i> strains depending on whether they own the key type III effector <i>exoU</i>.</p><p><strong>Importance: </strong><i>Pseudomonas aeruginosa</i> is a common cause of pneumonia in humans and a major nosocomial pathogen. People living with HIV (PLWH), even under antiretroviral therapy, are at risk of developing infectious diseases, such as bacterial pneumonia. The T3SS plays an important role in <i>P. aeruginosa</i> virulence. The T3SS can inject four effectors into the target cell cytosol, including the key effector ExoU that binds to PI(4,5)P2 on the inner leaflet of the plasma membrane. The potent phospholipase activity of ExoU rapidly induces cell death. HIV-Tat is present in the serum of PLWH. Circulating Tat enters cells and binds PI(4,5)P₂ with a very high affinity. Our results indicate that HIV-Tat interferes with the recruitment of ExoU by PI(4,5)P₂, thereby protecting macrophages from strains of <i>P. aeruginosa</i> that express ExoU. Tat, nevertheless, increased macrophage sensitivity to exoU-negative strains. HIV Tat could, therefore, modulate PLWH susceptibility to <i>P. aeruginosa</i>.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0067426"},"PeriodicalIF":4.0,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149183172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The <i>Agrobacterium fabrum</i> efflux pump PecM serves as a critical metabolic relief valve to maintain cellular homeostasis.","authors":"Arpita Ghosh, Ahmed Al-Tohamy, Fabrizio Donnarumma, Anne Grove","doi":"10.1128/msphere.00601-26","DOIUrl":"https://doi.org/10.1128/msphere.00601-26","url":null,"abstract":"<p><p><i>Agrobacterium fabrum</i> infects a wide range of plants, resulting in significant economic losses. In the rhizosphere, the bacterium is exposed to several stressors, including compounds secreted from other bacteria, fungi, or plants. <i>A. fabrum</i> encodes the efflux pump PecM for which the substrate is 4-hydroxybenzaldehyde, a compound that is both present in plant exudates and generated by bacteria during degradation of aromatic compounds. As an aromatic aldehyde, 4-hydroxybenzaldehyde is a chemically reactive electrophile that can react with cellular nucleophiles such as thiol groups on proteins and glutathione, leading to disruption of redox homeostasis. To assess the physiological consequences of <i>pecM</i> disruption, we compared the transcriptome and proteome profiles of wild-type and <i>pecM</i> disruption strains. While 30 genes were seen to be differentially expressed in the <i>pecM</i> disruption strain, 118 proteins differentially accumulated. Accumulating proteins included glutathione S-transferase and glutathione-dependent peroxiredoxin, both of which protect from oxidative stress. Consistent with this observation, the <i>pecM</i> disrupted strain was more resistant to oxidative stress. Across the genes and proteins detected in both data sets, there was no overall linear relationship, as reflected in a Pearson correlation of ~0. A marked depletion of bS21C, which is a component of the small ribosomal subunit, was observed; as one of three paralogs, its differential expression suggests the possibility that ribosome heterogeneity is part of adaptation to stress. Taken together, our data suggest that absence of PecM imposes a 4-hydroxybenzaldehyde-induced oxidative or electrophile stress and that PecM serves as a critical metabolic relief valve to maintain cellular homeostasis.</p><p><strong>Importance: </strong>Efflux pumps often receive attention in the context of protecting bacteria from environmental toxins such as antibiotics. However, they are also important for exporting metabolic intermediates that may otherwise disrupt cellular processes. Bacterial metabolism of aromatic compounds can generate 4-hydroxybenzaldehyde, which the bacteria may also encounter in the rhizosphere, and its intracellular accumulation would be expected to disrupt redox homeostasis. Here, we show that disruption of the <i>Agrobacterium fabrum</i> efflux pump PecM, which exports 4-hydroxybenzaldehyde, results in widespread proteomic remodeling, with marked accumulation of proteins associated with oxidative and electrophile stress. These findings emphasize the importance of efflux systems in preventing the accumulation of reactive intermediates, and they expand our understanding of how such efflux systems contribute to metabolic balance and global cellular adaptation in complex environmental niches such as the rhizosphere.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0060126"},"PeriodicalIF":4.0,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149137743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The synthesis of niclosamide derivative as a novel colistin adjuvant for reversing colistin resistance and its antibacterial activity with colistin <i>in vitro</i>.","authors":"Peiyi Liu, Yingbiao Li, Fanlun Ding, Dandan He, Yajun Zhai, Li Yuan, Xianya Wang, Guoyu Yang, Gongzheng Hu","doi":"10.1128/msphere.00593-26","DOIUrl":"https://doi.org/10.1128/msphere.00593-26","url":null,"abstract":"<p><p>Colistin (COL) serves as a last-line therapeutic agent against multidrug-resistant gram-negative bacteria (GNB) infections. Nevertheless, widespread clinical use of COL has led to severe bacterial resistance. The anthelmintic drug niclosamide (NIC) has been shown to enhance the activity of COL in combination therapy. Despite this synergistic advantage, the two compounds possess distinct physicochemical and pharmacokinetic properties. To enable simultaneous delivery of both drugs to the target site and maximize their synergistic antibacterial activity, we propose the synthesis of a prodrug conjugate linking COL and NIC. As a preparatory step toward a future COL-NIC conjugate, we synthesized and characterized the carboxymethylated derivative of NIC (Axilisuan [AXLS]) to reduce cytotoxicity, improve aqueous solubility, and maintain the NIC synergistic antibacterial effect with COL. AXLS was successfully synthesized and characterized by high-resolution mass spectrometry and proton nuclear magnetic resonance spectroscopy. Solubility studies showed that AXLS exhibited approximately 57-fold higher aqueous solubility than NIC. Both checkerboard assays and time-kill curve analyses indicated that AXLS displayed COL-enhancing activity comparable to that of NIC. Importantly, AXLS showed lower cytotoxicity than NIC, both alone and in combination with COL. Collectively, these findings provide crucial insights for the future development of synthetic strategies toward novel COL-NIC conjugates and offer a rational design framework for the chemical modification of salicylanilide-based antibacterial adjuvants against colistin-resistant GNB.IMPORTANCEColistin remains one of the few treatment options for infections caused by multidrug-resistant gram-negative bacteria, but increasing colistin resistance limits its clinical use. Niclosamide can potentiate colistin activity, but its poor aqueous solubility and safety liabilities limit further development. Here, we synthesized a carboxymethylated niclosamide derivative (Axilisuan) and found that it retained colistin-potentiating activity while showing markedly improved aqueous solubility and reduced <i>in vitro</i> toxicity compared with niclosamide. These findings support phenolic hydroxyl modification as a practical strategy for improving salicylanilide-based antibacterial adjuvants and provide a tractable intermediate for future development of colistin-niclosamide conjugates.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0059326"},"PeriodicalIF":4.0,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149137693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Members of the <i>Enterobacteriaceae</i> family produce a diffusible signal factor that modulates enteric pathogen virulence.","authors":"Paulina D Pavinski Bitar, Rimi Chowdhury, Erick Maosa Bosire, Ivan Keresztes, Michael J Stanhope, Craig Altier","doi":"10.1128/msphere.00403-26","DOIUrl":"https://doi.org/10.1128/msphere.00403-26","url":null,"abstract":"<p><p>Diffusible signal factors (DSFs) are a gammaproteobacterial family of quorum-sensing signals that mediate the transition between sessile and planktonic lifestyles. In addition to coordinating behavior within producing species, DSFs can be sensed by surrounding organisms, enabling interspecies \"eavesdropping.\" Several enteric pathogens that do not produce DSFs use these environmental signals to modulate their virulence, allowing them to conserve energy when expression of pathogenesis genes is not advantageous. Although DSFs have been detected in the gut, the microbial origins of these signals remain poorly defined. Here, we show that the ability to produce DSFs is more widespread among <i>Gammaproteobacteria</i> than previously appreciated. Using phylogenetic analysis, we identified more than 500 homologs of the DSF synthase RpfF that group into three distinct taxa. Our analysis further revealed evidence of horizontal gene transfer between <i>Burkholderiales</i>, a known reservoir of DSF production, and <i>Enterobacterales</i>, an order enriched in gut-associated bacteria. We found that <i>Enterobacterales</i> members <i>Cronobacter sakazakii</i> and <i>Enterobacter cloacae</i> produce the DSF <i>cis</i>-2-tetradecenoic acid in an <i>rpfF</i>-dependent manner. Furthermore, we demonstrated <i>cis</i>-2-tetradecenoic acid to be a potent repressor of virulence in the enteric pathogens <i>Salmonella enterica</i>, <i>Shigella flexneri</i>, and <i>Vibrio cholerae</i>. Finally, we have shown that in addition to its role in interspecies signaling, endogenous DSF production reduces biofilm formation and suppresses swarming in <i>E. cloacae</i>, while also promoting swimming motility, consistent with a shift to a free-living lifestyle. Together, these findings expand the known diversity of DSF signaling and identify gut-associated bacteria as a source of interspecies cues that shape pathogen behavior.</p><p><strong>Importance: </strong>Many bacterial pathogens rely on tightly regulated gene expression to cause disease, making virulence pathways attractive targets for new therapies. Diffusible signal factors (DSFs) are communication molecules that can suppress the virulence of several enteric pathogens, but their sources in the gut have not been well defined. Here, we identify gut-associated bacteria that produce the DSF molecule <i>cis</i>-2-tetradecenoic acid, capable of strongly repressing virulence in multiple enteric pathogens. Additionally, our work substantially expands the distribution of bacteria with the genetic capacity for DSF production, broadening the pool of candidate signal sources and paving the way for future discoveries in microbial communication.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0040326"},"PeriodicalIF":4.0,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149137598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microbial communities on station and train surfaces in Chennai Metro: insights into urban transit microbiome.","authors":"Vijaya Yuvaram Singh, Veerendra P Gadekar, Srijith Sasikumar, R M Rajeeva Lokshanan, V Senthamizhan, Bharath Prithiviraj, Himanshu Sinha, Karthik Raman","doi":"10.1128/msphere.00433-26","DOIUrl":"https://doi.org/10.1128/msphere.00433-26","url":null,"abstract":"<p><p>Urban public transport systems, particularly metro networks, serve as key hubs for microbial transmission, yet the urban microbiome in densely populated regions like India remains poorly characterized. Understanding these environments is crucial for public health, especially in light of the COVID-19 pandemic and growing concerns about antimicrobial resistance (AMR). This study is the first of its kind to investigate the microbial communities and the presence of AMR genes in the Chennai Metro system. We collected 96 surface swabs from 12 metro stations across two lines, focusing on surfaces that people frequently touch, such as handrails, kiosks, banisters, and ticket counters. Of the collected samples, 47 met quality control standards and were subjected to shotgun metagenomic sequencing, and 41 samples with more than 1 million reads were included in our analysis. Our findings indicate that surface type significantly influences microbial community structure, with kiosks exhibiting the highest microbial diversity. Comparative analysis with global urban data sets revealed unique microbial patterns specific to Chennai, including nine species that were notably more prevalent in our samples than in other urban transit systems worldwide. Furthermore, through pangenome analysis, we generated high-quality metagenome-assembled genomes that elucidated the adaptive strategies of dominant microbial species in this urban environment. Despite their relatively low abundance, several AMR families were widely distributed across the data set, with over 80% of samples containing at least one associated AMR gene, including families linked to rifamycins, multidrug resistance, and sulfonamides. This study lays a foundation for understanding the urban microbiome in India, emphasizing distinct regional characteristics and underscoring the need for sustained monitoring to mitigate disease transmission risks in high-density transit settings.</p><p><strong>Importance: </strong>Densely populated urban transit systems are critical hubs for microbial exchange, yet the mass transit microbiomes of Indian cities remain largely uncharacterized, representing a significant gap in global surveillance. Our study provides the first comprehensive metagenomic analysis of the Chennai Metro, a high-traffic transit network serving millions. Our findings highlight the unique environmental drivers shaping urban microbiota in India. Chennai, with over 12 million residents and a metro system serving over 105 million passengers annually, is an ideal yet uncharacterized environment for studying microbial dynamics, surface-microbe interactions, and environmental antimicrobial resistance reservoirs.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0043326"},"PeriodicalIF":4.0,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149137733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rate of osmotic pressure change in drying saliva microdroplets drives inactivation of model respiratory bacteria.","authors":"Taylor Medina, Beiping Luo, Thomas Peter, Htet Kyi Wynn, Tamar Kohn","doi":"10.1128/msphere.00594-26","DOIUrl":"https://doi.org/10.1128/msphere.00594-26","url":null,"abstract":"<p><p>Transmission of respiratory pathogens depends on their ability to remain viable in drying respiratory droplets, yet the physicochemical drivers of bacterial inactivation during droplet evaporation remain poorly quantified. This study combines controlled droplet experiments with physicochemical modeling to investigate how osmotic pressure dynamics influence bacterial survival. Using <i>Escherichia coli</i> and <i>Staphylococcus epidermidis</i> as gram-negative and gram-positive surrogates, respectively, we measured viability loss in artificial saliva droplets dried at multiple relative humidities, and reconstructed the time-resolved osmotic pressure using the respiratory aerosol model. Both organisms remained stable while droplets were liquid and osmotic pressure was low but lost viability as decreasing water activity during drying produced rapid increases in osmotic pressure. For droplets that effloresced, these changes were most pronounced around efflorescence. The extent of inactivation scaled log-linearly with the rate of osmotic pressure change: <i>E. coli</i> decayed faster than <i>S. epidermidis</i>, and relationships derived in artificial saliva predicted survival in independent phosphate-buffered saline experiments. A lower relative humidity produced a more rapid increase in osmotic pressure and greater inactivation. These results identify the rate of osmotic pressure change during respiratory droplet drying as a quantitative predictor of bacterial survival across different solution matrices and drying conditions.IMPORTANCEThe risk of infection by respiratory pathogens depends on how long microorganisms remain viable in respiratory particles after exhalation, yet the physical mechanisms controlling bacterial survival during droplet drying are not well defined. Evaporation of respiratory droplets concentrates salts and can impose sudden and extreme osmotic stress on microbes, but this process has been difficult to quantify because osmotic pressure cannot be measured directly inside microscopic droplets. Integration of droplet experiments with a physicochemical aerosol model shows that bacterial inactivation is governed primarily by the rate of osmotic pressure increase during droplet drying rather than by static values of humidity or solute concentration alone. This mechanism explains why rapid drying produces strong inactivation.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0059426"},"PeriodicalIF":4.0,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149128120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"mSphere of Influence: Is asymptomatic colonization really silent?","authors":"Brady L Spencer","doi":"10.1128/msphere.00250-26","DOIUrl":"https://doi.org/10.1128/msphere.00250-26","url":null,"abstract":"<p><p>Brady Spencer is a bacteriologist studying host-pathogen-microbiota interactions. In this mSphere of Influence article, she reflects on how two studies from Scott Hultgren's laboratory on mucosal imprinting following <i>Escherichia coli</i> bladder infection (V. P. O'Brien, T. J. Hannan, L. Yu, J. Livny, et al., Nat Microbiol 2:16196, 2016, http://dx.doi.org/10.1038/nmicrobiol.2016.196; S. K. Russell, J. K. Harrison, B. S. Olson, H. J. Lee, et al., Nat Microbiol 8:875-888, 2023, http://dx.doi.org/10.1038/s41564-023-01346-6) and work by J. C. Whitney, S. B. Peterson, J. Kim, M. Pazos, et al., eLife 6:e26938, 2017, https://doi.org/10.7554/eLife.26938) on T7SSb-mediated interbacterial antagonism shaped her approach to studying group B <i>Streptococcus</i> colonization and its potential long-term consequences at mucosal surfaces.</p>","PeriodicalId":19052,"journal":{"name":"mSphere","volume":" ","pages":"e0025026"},"PeriodicalIF":4.0,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149128051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}