mBio最新文献

{"title":"TNF signaling maintains local restriction of bacterial founder populations in intestinal and systemic sites during oral <i>Yersinia</i> infection.","authors":"Stefan T Peterson, Katherine G Dailey, Karthik Hullahalli, Daniel Sorobetea, Rina Matsuda, Jaydeen Sewell, Winslow Yost, Rosemary O'Neill, Suhas Bobba, Nicolai Apenes, Matthew E Sherman, George I Balazs, Charles-Antoine Assenmacher, Arin Cox, Matthew Lanza, Sunny Shin, Matthew K Waldor, Igor E Brodsky","doi":"10.1128/mbio.01779-25","DOIUrl":"10.1128/mbio.01779-25","url":null,"abstract":"<p><p>Enteroinvasive bacterial pathogens are responsible for an enormous worldwide disease burden that critically affects the young and immunocompromised. <i>Yersinia pseudotuberculosis</i> is a gram-negative enteric pathogen closely related to the plague agent <i>Y. pestis</i> that colonizes intestinal tissues, induces the formation of pyogranulomas along the intestinal tract, and disseminates to systemic organs following oral infection of experimental rodents. Prior studies proposed that systemic tissues were colonized by a pool of intestinal replicating bacteria distinct from populations within Peyer's patches and mesenteric lymph nodes. Whether bacteria within intestinal pyogranulomas serve as the source for systemic dissemination and the relationship between bacterial populations within different tissue sites is poorly defined. Moreover, the host factors that regulate <i>Yersinia</i> colonization and dissemination are not well understood. Here, we demonstrate using sequence tag-based analysis of microbial populations in R (STAMPR) that remarkably small founder populations independently colonize intestinal and systemic tissues. Notably, intestinal pyogranulomas contain clonal populations of bacteria that are restricted and do not spread to other tissues. However, <i>Yersinia</i> populations are shared among systemic organs and the blood, suggesting that systemic dissemination occurs via hematogenous spread. Finally, we demonstrate that TNF signaling is a key contributor to the bottlenecks limiting both initial colonization and subsequent dissemination of orally acquired bacterial populations. Altogether, this study reveals previously undescribed aspects of infection dynamics of enteric bacterial pathogens.IMPORTANCEDissemination of bacteria following intestinal infection can lead to severe disease, including sepsis, organ damage, and death. However, the intestinal bacterial population dynamics governing the colonization of mucosal and systemic tissues and the intestinal sites that seed systemic spread are not clear. <i>Yersinia pseudotuberculosis</i> is a rodent and human intestinal pathogen closely related to the plague agent and provides a natural rodent-adapted model to study systemic bacterial dissemination. Our findings define the infection dynamics of enteric <i>Yersinia</i> and the impact of the innate immune system on <i>Yersinia</i> colonization of the intestine and systemic organs.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0177925"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145023663","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":"Population-level bistability in <i>Pseudomonas aeruginosa</i> quorum sensing.","authors":"Bryce M Pettit Estell, Martin Schuster","doi":"10.1128/mbio.01713-25","DOIUrl":"10.1128/mbio.01713-25","url":null,"abstract":"<p><p>Quorum sensing (QS) is a widespread signaling mechanism in bacteria that coordinates collective behaviors according to population density. A foundational assumption in this field is that QS functions as a gene expression switch that synchronizes responses at the population level. While some studies indeed report homogeneous on/off transitions, others report heterogeneity at the cellular level, challenging the canonical view. To provide a formal context for these observations, we examined QS behavior at physiological steady state in the model bacterium <i>Pseudomonas aeruginosa</i>. We measured the expression of a central <i>las</i>-system component, the positively autoregulated signal synthase gene <i>lasI</i>, at the population and single-cell level. In support of the canonical view and predictions from mathematical modeling, we show that the <i>las</i> system exhibits population-level bistability, with the entire unimodal population of cells switching synchronously between two stable states. We also show that bistable state switching exhibits hysteresis, indicative of memory within the system, with induced cells maintaining activation at considerably lower densities than previously uninduced cells. We confirm these behaviors in a subset of other <i>las</i>-QS controlled genes. Our study experimentally proves population-level bistability as a central, emergent property in a native QS system, with implications for physiology, pathogenesis, and synthetic biology.IMPORTANCEThis research investigates quorum sensing (QS), a common bacterial communication mechanism that controls processes like virulence, biofilm formation, and microbial warfare. Our study experimentally proves the long-standing notion that native QS can function as a true genetic switch that synchronizes all-or-none responses in a population of cells. We employ the well-understood LasI/LasR QS system of the opportunistic pathogen <i>Pseudomonas aeruginosa</i> as a model. We show that the switch is bistable, with stable on and off states, and that it is hysteretic, with a type of memory that makes state-switching dependent on the initial condition. These properties impart robustness and stability to environmental changes akin to cellular developmental pathways; they have general implications for infection and its control, as well as genetic circuit design.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0171325"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145030013","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":"Rethinking large-scale phylogenomics with EukPhylo v.1.0, a flexible toolkit to enable phylogeny-informed data curation and analyses of diverse eukaryotic lineages.","authors":"Laura A Katz, Marie Leleu, Godwin Ani, Rebecca Gawron, Auden Cote-L'Heureux","doi":"10.1128/mbio.01770-25","DOIUrl":"10.1128/mbio.01770-25","url":null,"abstract":"<p><p>Eukaryotic diversity is largely microbial, with macroscopic lineages (plants, animals, and fungi) nesting among a plethora of diverse protists. Our understanding of the evolutionary relationships among eukaryotes is rapidly advancing through 'omics analyses, but phylogenomic analyses are challenging for microeukaryotes, particularly uncultivable lineages, as single-cell sequencing approaches generate a mixture of sequences from hosts, associated microbiomes, and contaminants. Moreover, many analyses of eukaryotic gene families and phylogenies rely on boutique data sets and methods that are challenging for other research groups to replicate. To address these challenges, we present EukPhylo v.1.0, a modular, user-friendly pipeline that enables effective data curation through phylogeny-informed contamination removal, estimation of homologous gene families (GFs), and generation of both multisequence alignments and gene trees. For the GF assignment, we provide the \"Hook Database\" of ~15,000 ancient GFs, which users can easily replace with a set of gene families of interest. We demonstrate the power of EukPhylo, including a suite of stand-alone utilities, through phylogenomic analyses of 500 conserved GFs sampled from 1,000 diverse species of eukaryotes, bacteria, and archaea. We show improvements in estimates of the eukaryotic tree of life, recovering clades that are well established in the literature, through successive rounds of curation using the EukPhylo contamination loop. The final trees corroborate numerous hypotheses in the literature (e.g., Opisthokonta, Rhizaria, Amoebozoa) while challenging others (e.g., CRuMs, Obazoa, Diaphoretickes). The flexibility and transparency of EukPhylo set new standards for curation of 'omics data for future studies.IMPORTANCEIlluminating the diversity of microbial lineages is essential for estimating the tree of life and characterizing principles of genome evolution. However, analyses of microbial eukaryotes (e.g., flagellates, amoebae) are complicated by both the paucity of reference genomes and the prevalence of contamination (e.g., by symbionts, microbiomes). EukPhylo v.1.0 enables taxon-rich analyses \"on the fly\" as users can choose optimal gene families for their focal taxa and then use replicable approaches to curate data in estimating both gene and species trees. With multiple entry points and curated data sets from up to 15,000 gene families from 1,000 taxa ready for use, EukPhylo provides a powerful launching point for researchers interested in the evolution of eukaryotes.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0177025"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144959220","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":"PIM1 orchestrates sepsis-associated inflammatory imbalance in CD4⁺ T cell subsets via cholesterol metabolism.","authors":"Mei Liu, Jia-Qi Wang, Jia-Ning Wang, Yi-Ni Sun, Si-Yao Li, Ya-Jing Fu, Yong-Jun Jiang, Zi-Ning Zhang, Hong Shang","doi":"10.1128/mbio.01680-25","DOIUrl":"10.1128/mbio.01680-25","url":null,"abstract":"<p><p>Sepsis, caused by an unbalanced host response to infection, remains a global health burden. The dysregulation between pro-inflammatory and anti-inflammatory responses is a primary driver of immune imbalance. As a central player in adaptive immunity, CD4⁺ T cells are crucial for maintaining this balance during sepsis by differentiating into various effector T cell subsets. Thus, elucidating the underlying mechanisms within the inflammatory and anti-inflammatory imbalance in CD4⁺ T cell subsets during sepsis is of great value. We first identified the proviral integration site for Moloney murine leukemia virus 1 (PIM1) as a significantly upregulated gene in CD4⁺ T cells from sepsis patients by conducting a comprehensive transcriptome meta-analysis. The expression of PIM1 was significantly elevated on CD4⁺ T cells from sepsis patients and was correlated with both SOFA and APACHE II scores. Moreover, we found that PIM1 promoted the differentiation of CD4⁺IFN-γ⁺ Th1 and CD4⁺IL-17A⁺ Th17 subsets while inhibiting the differentiation of CD25⁺FoxP3⁺ Tregs. Additionally, upon inhibiting PIM1 kinase activity in CD4⁺ T cells, RNA sequencing analysis revealed that the cholesterol metabolism gene, ATP-binding cassette transporter G1 (ABCG1), exhibited significant upregulation. More importantly, we found that the intracellular cholesterol content was decreased in CD4⁺ T cells after inhibiting the PIM1 kinase activity or knocking down PIM1. The portion of CD4⁺IFN-γ⁺ Th1 and CD4⁺IL-17A⁺ Th17 cells was recovered, and the CD4⁺CD25⁺FoxP3⁺ Tregs decreased after cholesterol supplementation to CD4⁺ T cells. These findings indicated that PIM1 may regulate the balance of Th1, Th17, and Treg subsets in a cholesterol-dependent manner in sepsis.IMPORTANCEThis study aims to elucidate the mechanism of the inflammatory and anti-inflammatory imbalance of CD4⁺ T cell subsets during sepsis. Our study provides evidence that PIM1 serves as a crucial regulator of sepsis-induced inflammation and elucidates that PIM1 participates in regulating the imbalance of Th1, Th17, and Treg subsets, further promoting inflammatory and anti-inflammatory imbalance in sepsis. Additionally, the cholesterol metabolism, potentially mediated by ABCG1, is implicated in PIM1's regulatory effect on the Th1, Th17, and Treg imbalance. Our study provides novel insights into the inflammatory imbalance during sepsis, which could facilitate the development of therapeutic strategies aimed at modulating the immune-inflammatory cascade in this condition.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0168025"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144959807","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":"PRRSV promotes bacterial infection by remodeling actin cytoskeleton and cell membrane proteins.","authors":"Xiao Liu, Fang Lv, Yanan Zhu, Yinan Meng, Bo Peng, Zifang Zheng, Yang Li, Lele Xu, Yingtong Feng, Jianwu Zhang, Shuqi Xiao","doi":"10.1128/mbio.01945-25","DOIUrl":"10.1128/mbio.01945-25","url":null,"abstract":"<p><p>Secondary infection is a worldwide problem in the prevention and control of viral infection. Secondary bacterial infection induced by porcine reproductive and respiratory syndrome virus (PRRSV) infection causes enormous economic losses, but the relevant mechanism remains unclear. We found that the infection of <i>Klebsiella pneumoniae</i> or <i>Streptococcus suis type 2</i> in the lungs of PRRSV-challenged piglets was significantly higher than the controls, and the infection of PRRSV, influenza A virus H1N1 (H1N1), and porcine circovirus type 2 (PCV2) also significantly increased the infection of the bacteria <i>in vitro</i>. Transcriptomic analysis revealed that PRRSV infection significantly altered the expression of cytoskeleton-related proteins, among which the expression of actin-binding protein filamin A (FLNA) was significantly increased, and knockdown of FLNA could significantly reduce bacterial invasion. Mechanistic studies found that FLNA drives actin cytoskeleton rearrangement by promoting F-actin generation, thereby facilitating bacterial invasion. Further studies found that PRRSV promoted bacterial adhesion by upregulating the expression of integrin α5 (ITGα5). ITGα5 could induce actin cytoskeleton rearrangement by promoting FLNA expression, thus aggravating bacterial invasion. Furthermore, we found that lentiviral shRNA-mediated knockdown of FLNA or ITGα5 significantly reduced bacterial infection in the lungs of mice and protected mice from death. These results suggest that the regulation of actin cytoskeleton and cell membrane proteins may be a conserved mechanism of virus-induced secondary bacterial infection.</p><p><strong>Importance: </strong>An important reason why porcine reproductive and respiratory syndrome virus (PRRSV) is difficult to control effectively is that it often causes severe secondary bacterial infections, which are usually attributed to the immunosuppression caused by PRRSV. However, the mechanism by which PRRSV infection leads to increased susceptibility of cells to bacterial infection has been largely overlooked. We revealed that PRRSV induced actin cytoskeleton rearrangement by upregulating FLNA expression, thereby aggravating bacterial invasion. PRRSV increased bacterial adhesion by promoting the ITGα5 expression, and the upregulation of ITGα5 could induce FLNA-mediated actin cytoskeleton rearrangement. Furthermore, we found that H1N1 and porcine circovirus type 2 infection also significantly promoted the expression of FLNA and ITGα5 and increased the infection of multiple bacteria. These results suggest that FLNA and ITGα5 play important roles in virus-induced secondary bacterial infection.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0194525"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145040547","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":"The <i>Staphylococcus aureus</i> esterase FmtA is essential for wall teichoic acid D-alanylation.","authors":"Kirsten A Berry, Mackenzie T A Verhoef, Zhiyong Zheng, Ronald S Flannagan, Telmo O Paiva, Stephanie E Gilbert, M Sameer Al-Abdul-Wahid, David E Heinrichs, Yves F Dufrêne, Georgina Cox","doi":"10.1128/mbio.02337-25","DOIUrl":"10.1128/mbio.02337-25","url":null,"abstract":"<p><p><i>Staphylococcus aureus</i> teichoic acids are anionic glycopolymers covalently attached to peptidoglycan (wall teichoic acids, WTAs) or anchored to the phospholipid membrane (lipoteichoic acids, LTAs). The post-synthetic addition of D-alanine (D-Ala) residues to these polymers modulates surface charge and contributes to pathogen survival in the host environment. Despite this importance, the underlying mechanisms controlling WTA D-alanylation remain a significant area for further investigation. Here, we demonstrate that the teichoic acid D-Ala esterase, FmtA, is essential for WTA D-alanylation. The inactivation of <i>fmtA</i> results in a more negative net surface charge, impacting host adhesion, biofilm formation, and cell aggregation. We found that LTA from <i>fmtA</i>-deficient strains retains normal D-alanylation levels, while WTA is almost devoid of D-Ala. These data support the notion that LTA provides the D-Ala for WTA modification, a process dependent on FmtA.IMPORTANCEThe D-alanine (D-Ala) modification of <i>Staphylococcus aureus</i> teichoic acids influences bacterial interactions and survival under stress. While this modification is important for host survival, the mechanisms underlying wall teichoic acid (WTA) D-alanylation remain unclear. A deeper understanding of this process could lead to the development of targeted therapies to combat <i>S. aureus</i> infections. We have identified FmtA as essential for this process, supporting the idea that lipoteichoic acid (LTA) provides the D-Ala used to modify WTAs. Our findings highlight a critical gap in understanding this mechanism: an acyltransferase must incorporate the D-Ala released from LTAs by FmtA into WTAs.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0233725"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145040550","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":"The transcription factor RttA contributes to sterol regulation and azole resistance in <i>Aspergillus fumigatus</i>.","authors":"Lukas Birštonas, Peter Hortschansky, Ingo Bauer, Ervin M Alcanzo, Alexander Kühbacher, Birte Mertens, Christoph Müller, Axel A Brakhage, Fabio Gsaller","doi":"10.1128/mbio.01854-25","DOIUrl":"10.1128/mbio.01854-25","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Major mechanisms of azole resistance in &lt;i&gt;Aspergillus fumigatus&lt;/i&gt; involve overexpression of the azole target protein encoded by &lt;i&gt;cyp51A&lt;/i&gt;. The elevated expression originates from the duplication of an enhancer element in its promoter, serving as a binding platform for AtrR and SrbA, two central transcription factors that orchestrate the activation of ergosterol biosynthesis genes and azole resistance. Alongside AtrR and SrbA, several other transcription factors were shown to be crucial to mediate azole tolerance. Here, we unveil RttA as a further protein involved in the regulation of ergosterol biosynthesis and azole resistance in &lt;i&gt;A. fumigatus&lt;/i&gt;. Because the gene was wrongly annotated, its encoded protein remained a protein with unclear function. Based on mapped RNA-seq reads, the coding sequence was corrected, yielding a DNA-binding protein comprising a Zn&lt;sub&gt;2&lt;/sub&gt;Cys&lt;sub&gt;6&lt;/sub&gt; binuclear zinc cluster. Domain analysis and structural comparisons implied similarity between RttA and &lt;i&gt;Neurospora crassa&lt;/i&gt; NcSR and yeast Upc2, both involved in sterol regulation and azole resistance. Through deletion and overexpression of &lt;i&gt;rttA&lt;/i&gt;, we confirm its role in azole resistance. Transcriptional profiling of &lt;i&gt;atrR&lt;/i&gt;, &lt;i&gt;srbA&lt;/i&gt;, and &lt;i&gt;rttA&lt;/i&gt; deletion mutants revealed that &lt;i&gt;rttA&lt;/i&gt; expression depends on both AtrR and SrbA. In addition, our analyses uncovered a positive regulatory role for RttA in the expression of efflux pump-encoding genes and sterol homeostasis through activation of &lt;i&gt;erg6&lt;/i&gt; expression. In agreement, the lack of &lt;i&gt;rttA&lt;/i&gt; led to a substantial accumulation of the Erg6 substrate lanosterol. Collectively, this work elucidates RttA as a transcription factor in the clinically important fungal pathogen &lt;i&gt;A. fumigatus&lt;/i&gt; involved in the regulation of ergosterol biosynthesis and azole tolerance.IMPORTANCEAzole antifungals are frontline treatments against &lt;i&gt;Aspergillus fumigatus&lt;/i&gt;, a major cause of life-threatening fungal infections. Resistance to azoles is a growing concern, often linked to increased expression of &lt;i&gt;cyp51A&lt;/i&gt;, which encodes the azole target enzyme. This upregulation depends on the transcription factors AtrR and SrbA, key activators of ergosterol biosynthesis genes. Here, we identify and characterize a previously misannotated gene, &lt;i&gt;rttA&lt;/i&gt;, encoding a Zn₂Cys₆ transcription factor structurally related to Upc2 and NcSR, sterol regulators in yeast and &lt;i&gt;Neurospora crassa&lt;/i&gt;. Functional analyses, including gene deletion, overexpression, and transcriptomics, show that RttA promotes azole resistance and regulates sterol homeostasis by activating &lt;i&gt;erg6&lt;/i&gt;, encoding sterol C24-methyltransferase. Loss of &lt;i&gt;rttA&lt;/i&gt; leads to lanosterol accumulation, indicating disrupted ergosterol biosynthesis. Moreover, &lt;i&gt;rttA&lt;/i&gt; expression depends on both AtrR and SrbA, placing RttA within their regulatory network. Our findings offer new insight into sterol regulation and antifungal resistance in","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0185425"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145040601","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":"AuxB interacts directly with GpsB and PknB to coordinate cell envelope processes that contribute to intrinsic antibiotic resistance in <i>Staphylococcus aureus</i>.","authors":"Tyler A Sisley, Youngseon Park, Ace George Santiago, Wanassa Beroual, Isabella A Sobolewski, Wonsik Lee, Joao A Paulo, Suzanne Walker","doi":"10.1128/mbio.01858-25","DOIUrl":"10.1128/mbio.01858-25","url":null,"abstract":"<p><p><i>Staphylococcus aureus</i>, a leading cause of serious infections, produces various factors important for intrinsic resistance to antibiotics. Understanding what intrinsic resistance factors do may enable strategies to potentiate existing antibiotics. The membrane protein AuxB is an intrinsic resistance factor that helps <i>S. aureus</i> withstand diverse compounds that target the cell envelope, but its cellular functions are unknown. We show here that AuxB is a four-pass transmembrane protein with an intracellular C-terminus that interacts directly with the cytosolic cell cycle regulator GpsB. We also show AuxB's membrane domain forms a homodimer that exists in equilibrium with a heterodimer of AuxB and PknB, a eukaryotic-like serine/threonine kinase that has been implicated in cell envelope processes. Shifting the equilibrium to favor AuxB-bound PknB impairs growth on tunicamycin, a condition where PknB is essential, which suggests that AuxB binding antagonizes a PknB function. To link PknB's domains to compound susceptibility phenotypes, we assessed the fitness of PknB variants under several conditions. We find that PknB's extracellular and kinase domains are not functionally interdependent but instead play distinct roles in withstanding cell envelope stress. AuxB evidently antagonizes functions of PknB's extracellular PASTA (<u>p</u>enicillin-binding protein <u>a</u>nd <u>S</u>er/<u>T</u>hr kinase-<u>a</u>ssociated) domain, the presence of which is beneficial under tunicamycin treatment regardless of whether the kinase domain is active. On compounds where the PASTA domain is deleterious, increasing the amount of AuxB-bound PknB can also ameliorate sensitivity. Collectively, our data suggest that AuxB, as a homodimer and through its interactions with GpsB and PknB, modulates cell envelope processes during cell growth and division.</p><p><strong>Importance: </strong><i>Staphylococcus aureus</i> is a leading cause of fatal infections worldwide. It encodes diverse genes that contribute to the organism's high intrinsic resistance to antibiotics. Understanding the biological roles of these genes and how their features contribute to intrinsic resistance may enable better antibiotic therapies. Here, we investigate AuxB, an intrinsic resistance factor to compounds that target the cell envelope. We find that AuxB interacts directly with the cell cycle regulator GpsB and the eukaryotic-like serine/threonine kinase PknB, another intrinsic resistance factor that is proposed to sense and respond to cell wall status. Based on our findings, we propose that AuxB impacts cell physiology through three mechanisms: (i) by antagonizing PknB's <u>p</u>enicillin-binding protein <u>a</u>nd <u>S</u>er/<u>T</u>hr kinase-<u>a</u>ssociated domain function; (ii) by coordinating the phosphorylation of cell division proteins; and (iii) by forming a homodimer that interacts with GpsB hexamers to enable the formation of extended GpsB interaction networks.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0185825"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144959686","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":"CCL20/CCR6 signaling modulates disease severity during the establishment of <i>Staphylococcus aureus</i> osteomyelitis.","authors":"Himanshu Meghwani, Javier Rangel-Moreno, Kyra M Sandercock, Motoo Saito, Katya A McDonald, Chloe M Kraft, Robert Constantine, Sophia Lenigk, Adryiana Rodriguez, Stephen L Kates, Jennifer H Jonason, Edward M Schwarz, Gowrishankar Muthukrishnan","doi":"10.1128/mbio.01413-25","DOIUrl":"10.1128/mbio.01413-25","url":null,"abstract":"<p><p>Chemokines are essential mediators of immune responses, and the CCL20/CCR6 chemokine signaling axis is known to be involved in inflammation, infectious diseases, and cancer progression. However, the role of the CCL20/CCR6 axis in host defense against <i>Staphylococcus aureus</i> osteomyelitis remains unknown. We hypothesized that the CCL20/CCR6 axis is critical for the recruitment and activation of immune cells against <i>S. aureus</i>, and the lack of CCL20 or its monogamous receptor CCR6 leads to exacerbation of <i>S. aureus</i> osteomyelitis. <i>In vitro</i> studies confirmed that osteoblasts and macrophages (M0 and M2 subtypes) secrete CCL20 following <i>S. aureus</i> exposure. Implant-associated osteomyelitis in C57BL/6, CCL20^-/-, and CCR6^-/- mice revealed an early increase in planktonic bacterial growth on day 1 and increased bacterial loads in soft tissue and bone on day 14 post-infection in both CCL20^-/- and CCR6^-/- mice. Immunohistochemistry and flow cytometry revealed that CCL20^-/- and CCR6^-/- mice have impaired recruitment of T cells, especially CCR6⁺ T cells, to the site of infection. Interestingly, CCR6^-/- mice exhibited increases in osteoclast numbers, reactive bone formation, and reduced bone mineral density. In a clinical pilot study, we observed a fivefold increase in serum CCL20 levels (<i>P</i> < 0.05) in <i>S. aureus</i> osteomyelitis patients (<i>n</i> = 23) vs uninfected controls (<i>n</i> = 10). Remarkably, serum CCL20 levels immediately following septic death were 100-fold higher vs uninfected patients (<i>P</i> < 0.05). Collectively, these results highlight the critical role of CCL20/CCR6-mediated host immunity during the establishment of <i>S. aureus</i> osteomyelitis and the potential of CCL20 as a biomarker of osteomyelitis-induced sepsis.</p><p><strong>Importance: </strong><i>Staphylococcus aureus</i> is the most common pathogen in orthopedic infections, and hard-to-treat strains (methicillin-resistant <i>S. aureus</i>) cause >50% of these infections. Thus, there is an urgent need to develop immunotherapies to treat these life-threatening infections. The role of the CCL20/CCR6 chemokine signaling axis on <i>S. aureus</i> osteomyelitis is unknown. In our efforts to uncover its role, we reveal that osteoblasts and macrophages secrete CCL20 in response to infection, and mice lacking CCL20 or its monogamous receptor CCR6 are more susceptible to <i>S. aureus</i> osteomyelitis. Mechanistically, we observed that increased infection severity in the knockout mice is associated with decreased T cell recruitment and increased osteoclastogenesis at the bone infection site. Importantly, in a clinical pilot study, we observed that CCL20 can be a useful biomarker of osteomyelitis-induced septic death. Overall, our study highlights the crucial immunomodulatory role that the CCL20/CCR6 axis plays during osteomyelitis.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0141325"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144959727","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":"Erratum for Tang et al., \"Gut microbe-derived betulinic acid alleviates sepsis-induced acute liver injury by inhibiting macrophage NLRP3 inflammasome in mice\".","authors":"Xuheng Tang, Tairan Zeng, Wenyan Deng, Wanning Zhao, Yanan Liu, Qiaobing Huang, Yiyu Deng, Weidang Xie, Wei Huang","doi":"10.1128/mbio.02792-25","DOIUrl":"10.1128/mbio.02792-25","url":null,"abstract":"","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0279225"},"PeriodicalIF":4.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145081185","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}