mBio最新文献

{"title":"Characterization and functional analysis of <i>Toxoplasma</i> Golgi-associated proteins identified by proximity labeling.","authors":"Rebecca R Pasquarelli, Justin J Quan, Emily S Cheng, Vivian Yang, Timmie A Britton, Jihui Sha, James A Wohlschlegel, Peter J Bradley","doi":"10.1128/mbio.02380-24","DOIUrl":"10.1128/mbio.02380-24","url":null,"abstract":"<p><p><i>Toxoplasma gondii</i> possesses a highly polarized secretory pathway that contains both broadly conserved eukaryotic organelles and unique apicomplexan organelles, which play essential roles in the parasite's lytic cycle. As in other eukaryotes, the <i>T. gondii</i> Golgi apparatus sorts and modifies proteins prior to their distribution to downstream organelles. Many of the typical trafficking factors found involved in these processes are missing from apicomplexan genomes, suggesting that these parasites have evolved unique proteins to fill these roles. Here, we identify a Golgi-localizing protein (ULP1), which is structurally similar to the eukaryotic trafficking factor p115/Uso1. We demonstrate that depletion of ULP1 leads to a dramatic reduction in parasite fitness that is the result of defects in microneme secretion, invasion, replication, and egress. Using ULP1 as bait for TurboID proximity labeling and immunoprecipitation, we identify 11 more Golgi-associated proteins and demonstrate that ULP1 interacts with the <i>T. gondii</i>-conserved oligomeric Golgi (COG) complex. These proteins include both conserved trafficking factors and parasite-specific proteins. Using a conditional knockdown approach, we assess the effect of each of these 11 proteins on parasite fitness. Together, this work reveals a diverse set of <i>T. gondii</i> Golgi-associated proteins that play distinct roles in the secretory pathway. As several of these proteins are absent outside of the Apicomplexa, they represent potential targets for the development of novel therapeutics against these parasites.</p><p><strong>Importance: </strong>Apicomplexan parasites such as <i>Toxoplasma gondii</i> infect a large percentage of the world's population and cause substantial human disease. These widespread pathogens use specialized secretory organelles to infect their host cells, modulate host cell functions, and cause disease. While the functions of the secretory organelles are now better understood, the Golgi apparatus of the parasite remains largely unexplored, particularly regarding parasite-specific innovations that may help direct traffic intracellularly. In this work, we characterize ULP1, a protein that is unique to parasites but shares structural similarity to the eukaryotic trafficking factor p115/Uso1. We show that ULP1 plays an important role in parasite fitness and demonstrate that it interacts with the conserved oligomeric Golgi (COG) complex. We then use ULP1 proximity labeling to identify 11 additional Golgi-associated proteins, which we functionally analyze via conditional knockdown. This work expands our knowledge of the <i>Toxoplasma</i> Golgi apparatus and identifies potential targets for therapeutic intervention.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0238024"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559087/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142349635","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":"Novel isolates expand the physiological diversity of <i>Prochlorococcus</i> and illuminate its macroevolution.","authors":"Jamie W Becker, Shaul Pollak, Jessie W Berta-Thompson, Kevin W Becker, Rogier Braakman, Keven D Dooley, Thomas Hackl, Allison Coe, Aldo Arellano, Kristen N LeGault, Paul M Berube, Steven J Biller, Andrés Cubillos-Ruiz, Benjamin A S Van Mooy, Sallie W Chisholm","doi":"10.1128/mbio.03497-23","DOIUrl":"10.1128/mbio.03497-23","url":null,"abstract":"&lt;p&gt;&lt;p&gt;&lt;i&gt;Prochlorococcus&lt;/i&gt; is a diverse picocyanobacterial genus and the most abundant phototroph on Earth. Its photosynthetic diversity divides it into high-light (HL)- or low-light (LL)-adapted groups representing broad phylogenetic grades-each composed of several monophyletic clades. Here, we physiologically characterize four new &lt;i&gt;Prochlorococcus&lt;/i&gt; strains isolated from below the deep chlorophyll maximum in the North Pacific Ocean. We combine these physiological properties with genomic analyses to explore the evolution of photosynthetic antennae and discuss potential macroevolutionary implications. The isolates belong to deeply branching low-light-adapted clades that have no other cultivated representatives and display some unusual characteristics. For example, despite its otherwise low-light-adapted physiological characteristics, strain MIT1223 has low chl &lt;i&gt;b&lt;sub&gt;2&lt;/sub&gt;&lt;/i&gt; content similar to high-light-adapted strains. Isolate genomes revealed that each strain contains a unique arsenal of pigment biosynthesis and binding alleles that have been horizontally acquired, contributing to the observed physiological diversity. Comparative genomic analysis of all picocyanobacteria reveals that Pcb, the major pigment carrying protein in &lt;i&gt;Prochlorococcus&lt;/i&gt;, greatly increased in copy number and diversity per genome along a branch that coincides with the loss of facultative particle attachment. Collectively, these observations support a recently developed macroevolutionary model, in which niche-constructing radiations allowed ancestral lineages of picocyanobacteria to transition from a particle-attached to planktonic lifestyle and broadly colonize the euphotic zone.&lt;b&gt;IMPORTANCE&lt;/b&gt;The marine cyanobacterium, &lt;i&gt;Prochlorococcus&lt;/i&gt;, is among the Earth's most abundant organisms, and much of its genetic and physiological diversity remains uncharacterized. Although field studies help reveal the scope of diversity, cultured isolates allow us to link genomic potential to physiological processes, illuminate eco-evolutionary feedbacks, and test theories arising from comparative genomics of wild cells. Here, we report the isolation and characterization of novel low-light (LL)-adapted &lt;i&gt;Prochlorococcus&lt;/i&gt; strains that fill in multiple evolutionary gaps. These new strains are the first cultivated representatives of the LLVII and LLVIII paraphyletic grades of &lt;i&gt;Prochlorococcus&lt;/i&gt;, which are broadly distributed in the lower regions of the ocean euphotic zone. Each of these grades is a unique, highly diverse section of the &lt;i&gt;Prochlorococcus&lt;/i&gt; tree that separates distinct ecological groups: the LLVII grade branches between monophyletic clades that have facultatively particle-associated and constitutively planktonic lifestyles, whereas the LLVIII grade lies along the branch that leads to all high-light (HL)-adapted clades. Characterizing strains and genomes from these grades yields insights into the large-scale evolution of &lt;i&gt;Prochlorococcus&lt;/i&gt;. Th","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0349723"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559063/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142469442","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 <i>Candida auris</i> Hog1 MAP kinase is essential for the colonization of murine skin and intradermal persistence.","authors":"Raju Shivarathri, Manju Chauhan, Abhishek Datta, Diprasom Das, Adela Karuli, Ariel Aptekmann, Sabrina Jenull, Karl Kuchler, Shankar Thangamani, Anuradha Chowdhary, Jigar V Desai, Neeraj Chauhan","doi":"10.1128/mbio.02748-24","DOIUrl":"10.1128/mbio.02748-24","url":null,"abstract":"<p><p><i>Candida auris</i>, a multidrug-resistant human fungal pathogen, was first identified in 2009 in Japan. Since then, systemic <i>C. auris</i> infections have now been reported in more than 50 countries, with mortality rates of 30%-60%. A major contributing factor to its high inter- and intrahospital clonal transmission is that <i>C. auris,</i> unlike most <i>Candida</i> species, displays unique skin tropism and can stay on human skin for a prolonged period. However, the molecular mechanisms responsible for <i>C. auris</i> skin colonization, intradermal persistence, and systemic virulence are poorly understood. Here, we report that <i>C. auris</i> Hog1 mitogen-activated protein kinase is essential for efficient skin colonization, intradermal persistence as well as systemic virulence. RNA-seq analysis of wild-type parental and <i>hog1</i>Δ mutant strains revealed marked downregulation of genes involved in processes such as cell adhesion, cell wall rearrangement, and pathogenesis in <i>hog1</i>Δ mutant compared to the wild-type parent. Consistent with these data, we found a prominent role for Hog1 in maintaining cell wall architecture, as the <i>hog1</i>Δ mutant demonstrated a significant increase in cell-surface β-glucan exposure and a concomitant reduction in chitin content. Additionally, we observed that Hog1 was required for biofilm formation <i>in vitro</i> and fungal survival when challenged with primary murine macrophages and neutrophils <i>ex vivo</i>. Collectively, these findings have important implications for understanding the <i>C. auris</i> skin adherence mechanisms and penetration of skin epithelial layers preceding bloodstream infections.</p><p><strong>Importance: </strong><i>Candida auris</i> is a World Health Organization fungal priority pathogen and an urgent public health threat recognized by the Centers for Disease Control and Prevention. <i>C. auris</i> has a unique ability to colonize human skin. It also persists on abiotic surfaces in healthcare environments for an extended period of time. These attributes facilitate the inter- and intrahospital clonal transmission of <i>C. auris</i>. Therefore, understanding <i>C. auris</i> skin colonization mechanisms is critical for infection control, especially in hospitals and nursing homes. However, despite its profound clinical relevance, the molecular and genetic basis of <i>C. auris</i> skin colonization mechanisms are poorly understood. Herein, we present data on the identification of the Hog1 MAP kinase as a key regulator of <i>C. auris</i> skin colonization. These findings lay the foundation for further characterization of unique mechanisms that promote fungal persistence on human skin.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0274824"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11558994/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142469445","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 ribosome-associated quality control pathway supports survival in the absence of non-stop ribosome rescue factors.","authors":"Katrina Callan, Cassidy R Prince, Heather A Feaga","doi":"10.1128/mbio.02322-24","DOIUrl":"10.1128/mbio.02322-24","url":null,"abstract":"<p><p>In bacteria, if a ribosome translates an mRNA lacking a stop codon it becomes stalled at the 3' end of the message. These ribosomes must be rescued by <i>trans</i>-translation or the alternative rescue factors (ArfA or ArfB). However, mounting evidence suggests that the ribosome quality control (RQC) pathway may also rescue non-stop ribosomes. Here, we surveyed the conservation of ribosome rescue pathways in >15,000 bacterial genomes. We found that <i>trans</i>-translation is conserved in >97% of bacterial genomes, while the other rescue pathways are restricted to particular phyla. We did not detect the gene encoding RqcH, the major mediator of RQC, in Proteobacteria (Pseudomonadota). In all Proteobacteria investigated to date, <i>trans</i>-translation is essential in the absence of the Arf proteins. Therefore, we tested whether expression of RQC components from <i>Bacillus subtilis</i> could rescue viability in the absence of <i>trans</i>-translation and ArfA in <i>Escherichia coli</i>. We found that the RQC pathway indeed functions in <i>E. coli</i> and rescues the well-documented synthetic lethal phenotype of ∆<i>ssrA</i>∆<i>arfA</i>. Moreover, we show that the RQC pathway in <i>B. subtilis</i> is essential in the absence of <i>trans</i>-translation and ArfA, further supporting a role for the RQC pathway in the rescue of non-stop ribosomes. Finally, we report a strong co-occurrence between RqcH and the ribosome splitting factor MutS2, but present experimental evidence that there are likely additional ribosome splitting factors beyond MutS2 in <i>B. subtilis</i>. Altogether, our work supports a role for RQC in non-stop ribosome rescue and provides a broad survey of ribosome rescue pathways in diverse bacteria.</p><p><strong>Importance: </strong>In bacteria, it is estimated that 2%-4% of all translation reactions terminate with the ribosome stalled on a damaged mRNA lacking a stop codon. Mechanisms that rescue these ribosomes are essential for viability. We determined the functional overlap between the ribosome quality control pathway and the classical non-stop rescue systems [alternative rescue factor (ArfA) and <i>trans</i>-translation] in a representative Firmicute and Proteobacterium, phyla that are evolutionarily distinct. Furthermore, we used a bioinformatics approach to examine the conservation and overlap of various ribosome rescue systems in >15,000 species throughout the bacterial domain. These results provide key insights into ribosome rescue in diverse phyla.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0232224"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142622365","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 changing roles of scientific journals.","authors":"Arturo Casadevall, Lorraine F Clark, Ferric C Fang","doi":"10.1128/mbio.02515-24","DOIUrl":"10.1128/mbio.02515-24","url":null,"abstract":"<p><p>After centuries of relative stability, the scientific publishing world has undergone tremendous disruption and change during the first decades of the 21st century. The causes for disruption can be traced to the information revolution, which brought such benefits as rapid publication, greater connectivity, and ready access to large databases, along with less desirable practices including image manipulation, plagiarism, and other ethical transgressions. The information revolution has driven the proliferation of journals, expansion of for-profit academic publishing, and empowerment of the open-access movement, each of which has exerted new financial pressures on traditional publishing models. As journals became the focal point for ethical concerns in science, they have adapted by increasing the scope of their duties, which now include archiving of data, enforcement of good practices, establishment of standards for rigor, and training the next generation of reviewers and editors. Here, we consider the seismic changes occurring in scientific publishing and place them into the context of a rapidly changing landscape of scientific and publishing norms.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0251524"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559086/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142372196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"<i>Plasmodium falciparum</i> protein phosphatase PP7 is required for early ring-stage development.","authors":"Avnish Patel, Aline Fréville, Joshua A Rey, Helen R Flynn, Konstantinos Koussis, Mark J Skehel, Michael J Blackman, David A Baker","doi":"10.1128/mbio.02539-24","DOIUrl":"10.1128/mbio.02539-24","url":null,"abstract":"<p><p>We previously reported that the <i>Plasmodium falciparum</i> putative serine/threonine protein phosphatase 7 (PP7) is a high-confidence substrate of the cAMP-dependent protein kinase (PKA). Here we explore the function of PP7 in asexual <i>P. falciparum</i> blood stage parasites. We show that conditional disruption of PP7 leads to a severe growth arrest. We show that PP7 is a calcium-dependent phosphatase that interacts with calmodulin and calcium-dependent protein kinase 1 (CDPK1), consistent with a role in calcium signaling. Notably, PP7 was found to be dispensable for erythrocyte invasion, but was crucial for ring-stage development, with PP7-null parasites arresting shortly following invasion and showing no transition to ameboid forms. Phosphoproteomic analysis revealed that PP7 may regulate certain PKAc substrates. Its interaction with calmodulin and CDPK1 further emphasizes a role in calcium signaling, while its impact on early ring development and PKAc substrate phosphorylation underscores its importance in parasite development.</p><p><strong>Importance: </strong><i>Plasmodium falciparum</i> causes malaria and is responsible for more than 600,000 deaths each year. Although effective drugs are available to treat disease, the spread of drug-resistant parasites endangers their future efficacy. It is hoped that a better understanding of the biology of malaria parasites will help us to discover new drugs to tackle the resistance problem. Our work is focused on the cell signaling mechanisms that control the development of the parasite throughout its complex life cycle. All signal transduction pathways are ultimately regulated by reversible protein phosphorylation by protein kinase and protein phosphatase enzymes. In this study, we investigate the function of calcium-dependent protein phosphatase PP7 and show that it is essential for the development of ring-stage parasites following the invasion of human erythrocytes. Our results contribute to the understanding of the erythrocytic stages of the parasite life cycle that cause malaria pathology.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0253924"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559042/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142469434","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":"EF-hand calcium sensor, EfhP, controls transcriptional regulation of iron uptake by calcium in <i>Pseudomonas aeruginosa</i>.","authors":"Jacob Burch-Konda, Biraj B Kayastha, Myriam Achour, Aya Kubo, Mackenzie Hull, Reygan Braga, Lorelei Winton, Rendi R Rogers, Erika I Lutter, Marianna A Patrauchan","doi":"10.1128/mbio.02447-24","DOIUrl":"10.1128/mbio.02447-24","url":null,"abstract":"&lt;p&gt;&lt;p&gt;The human pathogen &lt;i&gt;Pseudomonas aeruginosa&lt;/i&gt; (&lt;i&gt;Pa&lt;/i&gt;) poses a major risk for a range of severe infections, particularly lung infections in patients suffering from cystic fibrosis (CF). As previously reported, the virulent behavior of this pathogen is enhanced by elevated levels of Ca&lt;sup&gt;2+&lt;/sup&gt; that are commonly present in CF nasal and lung fluids. In addition, a Ca&lt;sup&gt;2+&lt;/sup&gt;-binding EF-hand protein, EfhP (PA4107), was partially characterized and shown to be critical for the Ca&lt;sup&gt;2+&lt;/sup&gt;-regulated virulence in &lt;i&gt;P. aeruginosa&lt;/i&gt;. Here, we describe the rapid (10 min, 60 min), and adaptive (12 h) transcriptional responses of PAO1 to elevated Ca&lt;sup&gt;2+&lt;/sup&gt; detected by genome-wide RNA sequencing and show that &lt;i&gt;efhP&lt;/i&gt; deletion significantly hindered both rapid and adaptive Ca&lt;sup&gt;2+&lt;/sup&gt; regulation. The most differentially regulated genes included multiple Fe sequestering mechanisms, a large number of extracytoplasmic function sigma factors (ECFσ), and several virulence factors, such as the production of pyocins. The Ca&lt;sup&gt;2+&lt;/sup&gt; regulation of Fe uptake was also observed in CF clinical isolates and appeared to involve the global regulator Fur. In addition, we showed that the &lt;i&gt;efhP&lt;/i&gt; transcription is controlled by Ca&lt;sup&gt;2+&lt;/sup&gt; and Fe, and this regulation required a Ca&lt;sup&gt;2+&lt;/sup&gt;-dependent two-component regulatory system CarSR. Furthermore, the &lt;i&gt;efhP&lt;/i&gt; expression is significantly increased in CF clinical isolates and upon pathogen internalization into epithelial cells. Overall, the results established for the first time that Ca&lt;sup&gt;2+&lt;/sup&gt; controls Fe sequestering mechanisms in &lt;i&gt;P. aeruginosa&lt;/i&gt; and that EfhP plays a key role in the regulatory interconnectedness between Ca&lt;sup&gt;2+&lt;/sup&gt; and Fe signaling pathways, the two distinct and important signaling pathways that guide the pathogen's adaptation to the host.IMPORTANCE&lt;i&gt;Pseudomonas aeruginosa&lt;/i&gt; (&lt;i&gt;Pa&lt;/i&gt;) poses a major risk for severe infections, particularly in patients suffering from cystic fibrosis (CF). For the first time, kinetic RNA sequencing analysis identified &lt;i&gt;Pa&lt;/i&gt; rapid and adaptive transcriptional responses to Ca&lt;sup&gt;2+&lt;/sup&gt; levels consistent with those present in CF respiratory fluids. The most highly upregulated processes include iron sequestering, iron starvation sigma factors, and self-lysis factors pyocins. An EF-hand Ca&lt;sup&gt;2+&lt;/sup&gt; sensor, EfhP, is required for at least 1/3 of the Ca&lt;sup&gt;2+&lt;/sup&gt; response, including the majority of the iron uptake mechanisms and the production of pyocins. Transcription of &lt;i&gt;efhP&lt;/i&gt; itself is regulated by Ca&lt;sup&gt;2+&lt;/sup&gt; and Fe, and increases during interactions with host epithelial cells, suggesting the protein's important role in &lt;i&gt;Pa&lt;/i&gt; infections. The findings establish the regulatory interconnectedness between Ca&lt;sup&gt;2+&lt;/sup&gt; and iron signaling pathways that shape &lt;i&gt;Pa&lt;/i&gt; transcriptional responses. Therefore, understanding Pa's transcriptional response to Ca&lt;sup&gt;2+&lt;/sup&gt; and associa","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0244724"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559002/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142469437","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":"Gladiolin produced by pathogenic <i>Burkholderia</i> synergizes with amphotericin B through membrane lipid rearrangements.","authors":"Claudia Simm, Tzong-Hsien Lee, Harshini Weerasinghe, Dean Walsh, Ioanna T Nakou, Madhu Shankar, Wai Chung Tse, Yu Zhang, Rebecca Inman, Roger J Mulder, Freya Harrison, Marie-Isabel Aguilar, Gregory L Challis, Ana Traven","doi":"10.1128/mbio.02611-24","DOIUrl":"10.1128/mbio.02611-24","url":null,"abstract":"<p><p>Amphotericin B (AmpB) is an effective but toxic antifungal drug. Thus, improving its activity/toxicity relationship is of interest. AmpB disrupts fungal membranes by two proposed mechanisms: ergosterol sequestration from the membrane and pore formation. Whether these two mechanisms operate in conjunction and how they could be potentiated remains to be fully understood. Here, we report that gladiolin, a polyketide antibiotic produced by <i>Burkholderia gladioli</i>, is a strong potentiator of AmpB and acts synergistically against <i>Cryptococcus</i> and <i>Candida</i> species, including drug-resistant <i>C. auris</i>. Gladiolin also synergizes with AmpB against drug-resistant fungal biofilms, while exerting no mammalian cytotoxicity. To explain the mechanism of synergy, we show that gladiolin interacts with membranes via a previously unreported binding mode for polyketides. Moreover, gladiolin modulates lipid binding by AmpB and, in combination, causes faster and more pronounced lipid rearrangements relative to AmpB alone which include membrane thinning consistent with ergosterol extraction, areas of thickening, pore formation, and increased membrane destruction. These biophysical data provide evidence of a functional interaction between gladiolin and AmpB at the membrane interface. The data further indicate that the two proposed AmpB mechanisms (ergosterol sequestration and pore formation) act in conjunction to disrupt membranes, and that gladiolin synergizes by enhancing both mechanisms. Collectively, our findings shed light on AmpB's mechanism of action and characterize gladiolin as an AmpB potentiator, showing an antifungal mechanism distinct from its proposed antibiotic activity. We shed light on the synergistic mechanism at the membrane, and provide insights into potentiation strategies to improve AmpB's activity/toxicity relationship.</p><p><strong>Importance: </strong>Amphotericin B (AmpB) is one of the oldest antifungal drugs in clinical use. It is an effective therapeutic, but it comes with toxicity issues due to the similarities between its fungal target (the membrane lipid ergosterol) and its mammalian counterpart (cholesterol). One strategy to improve its activity/toxicity relationship is by combinatorial therapy with potentiators, which would enable a lower therapeutic dose of AmpB. Here, we report on the discovery of the antibiotic gladiolin as a potentiator of AmpB against several priority human fungal pathogens and fungal biofilms, with no increased toxicity against mammalian cells. We show that gladiolin potentiates AmpB by increasing and accelerating membrane damage. Our findings also provide insights into the on-going debate about the mechanism of action of AmpB by indicating that both proposed mechanisms, extraction of ergosterol from membranes and pore formation, are potentiated by gladiolin.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0261124"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559049/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142469439","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":"Short-range C-signaling restricts cheating behavior during <i>Myxococcus xanthus</i> development.","authors":"Y Hoang, Joshua Franklin, Yann S Dufour, Lee Kroos","doi":"10.1128/mbio.02440-24","DOIUrl":"10.1128/mbio.02440-24","url":null,"abstract":"<p><p><i>Myxococcus xanthus</i> uses short-range C-signaling to coordinate multicellular mound formation with sporulation during fruiting body development. A <i>csgA</i> mutant deficient in C-signaling can cheat on wild type (WT) in mixtures and form spores disproportionately, but our understanding of cheating behavior is incomplete. We subjected mixtures of WT and <i>csgA</i> cells at different ratios to co-development and used confocal microscopy and image analysis to quantify the arrangement and morphology of cells. At a ratio of one WT to four <i>csgA</i> cells (1:4), mounds failed to form. At 1:2, only a few mounds and spores formed. At 1:1, mounds formed with a similar number and arrangement of WT and <i>csgA</i> rods early in development, but later the number of <i>csgA</i> spores near the bottom of these nascent fruiting bodies (NFBs) exceeded that of WT. This cheating after mound formation involved <i>csgA</i> forming spores at a greater rate, while WT disappeared at a greater rate, either lysing or exiting NFBs. At 2:1 and 4:1, <i>csgA</i> rods were more abundant than expected throughout the biofilm both before and during mound formation, and cheating continued after mound formation. We conclude that C-signaling restricts cheating behavior by requiring sufficient WT cells in mixtures. Excess cheaters may interfere with positive feedback loops that depend on the cellular arrangement to enhance C-signaling during mound building. Since long-range signaling could not likewise communicate the cellular arrangement, we propose that C-signaling was favored evolutionarily and that other short-range signaling mechanisms provided selective advantages in bacterial biofilm and multicellular animal development.</p><p><strong>Importance: </strong>Bacteria communicate using both long- and short-range signals. Signaling affects community composition, structure, and function. Adherent communities called biofilms impact medicine, agriculture, industry, and the environment. To facilitate the manipulation of biofilms for societal benefits, a better understanding of short-range signaling is necessary. We investigated the susceptibility of short-range C-signaling to cheating during <i>Myxococcus xanthus</i> biofilm development. A mutant deficient in C-signaling fails to form mounds containing spores (i.e., fruiting bodies) but cheats on C-signaling by wild type in starved cell mixtures and forms spores disproportionately. We found that cheating requires sufficient wild-type cells in the initial mix and can occur both before mound formation and later during the sporulation stage of development. By restricting cheating behavior, short-range C-signaling may have been favored evolutionarily rather than long-range diffusible signaling. Cheating restrictions imposed by short-range signaling may have likewise driven the evolution of multicellularity broadly.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0244024"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559036/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142469444","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":"What are the essential determinants of human papillomavirus carcinogenesis?","authors":"Karl Munger, Elizabeth A White","doi":"10.1128/mbio.00462-24","DOIUrl":"10.1128/mbio.00462-24","url":null,"abstract":"<p><p>Human papillomavirus (HPV) infection is the leading viral cause of cancer. Over the past several decades, research on HPVs has provided remarkable insight into human cell biology and into the pathology of viral and non-viral cancers. The HPV E6 and E7 proteins engage host cellular proteins to establish an environment in infected cells that is conducive to virus replication. They rewire host cell signaling pathways to promote proliferation, inhibit differentiation, and limit cell death. The activity of the \"high-risk\" HPV E6 and E7 proteins is so potent that their dysregulated expression is sufficient to drive the initiation and maintenance of HPV-associated cancers. Consequently, intensive research efforts have aimed to identify the host cell targets of E6 and E7, in part with the idea that some or all of the virus-host interactions would be essential cancer drivers. These efforts have identified a large number of potential binding partners of each oncoprotein. However, over the same time period, parallel research has revealed that a relatively small number of genetic mutations drive carcinogenesis in most non-viral cancers. We therefore propose that a high-priority goal is to identify which of the many targets of E6 and E7 are critical drivers of HPV carcinogenesis. By identifying the cancer-driving targets of E6 and E7, it should be possible to better understand the distinct roles of other targets, perhaps in the viral life cycle, and to focus efforts to develop anti-cancer therapies on the subset of virus-host interactions for which therapeutic intervention would have the greatest impact.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0046224"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11558995/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142372197","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}