mBio最新文献

{"title":"The alphaherpesvirus gE/gI glycoprotein complex and proteases jointly orchestrate invasion across the host's upper respiratory epithelial barrier.","authors":"E Van Crombrugge, X Ren, S Glorieux, I Zarak, W Van den Broeck, C Bachert, N Zhang, T Van Zele, D Kim, G A Smith, K Laval, H Nauwynck","doi":"10.1128/mbio.01873-24","DOIUrl":"10.1128/mbio.01873-24","url":null,"abstract":"<p><p>Alphaherpesviruses, including herpes simplex virus type 1 (HSV-1), pseudorabies virus (PRV), and bovine herpesvirus type 1 (BoHV-1), are significant pathogens affecting humans and animals. These viruses penetrate the upper respiratory tract mucosa, yet the mechanisms facilitating this invasion are not fully understood. This study investigates the role of the gE/gI glycoprotein complex and proteases in mucosal invasion by these viruses. Using species-specific respiratory mucosal explants, we observed that the removal of extracellular calcium disrupts epithelial junction integrity, enhancing viral infection across all viruses and suggesting a common mechanism of targeting a basolaterally located receptor. PRV exhibited significantly faster replication and deeper invasion compared to HSV-1 and BoHV-1. The gE glycoprotein was consistently polarized at the basement membrane across all viruses, indicating a critical role in the process of viral entry and subsequent spread through the epithelium. In this context, \"infection\" refers to the virus's attachment to its cell-surface receptor, entry into the cell, and completion of the viral life cycle, culminating in the production of progeny virions. Notably, in gE/gI null mutants of PRV and HSV-1, while the infection was not abortive and the viral life cycle was completed, the infection was delayed, and the invasion into the deeper layers of the epithelium and underlying mucosa was significantly reduced. In BoHV-1 mutants, this effect was even more pronounced, with infection restricted to the apical cells, failing to progress to the basal cells. In addition, PRV and HSV-1 invasion involved serine protease activity, unlike BoHV-1, which correlates with its slower invasion pace. Notably, the protease facilitating PRV invasion was identified as a urokinase plasminogen activator (uPA), while the specific protease for HSV-1 remains unidentified. These findings highlight the critical roles of the gE/gI complex and proteases in alphaherpesvirus pathogenesis, offering potential targets for therapeutic intervention.</p><p><strong>Importance: </strong>Herpes simplex virus type 1 (HSV-1) infections are a worldwide issue. More than three billion people are infected with HSV-1 globally. Although most infections with HSV-1 occur subclinically, severe symptoms and complications are numerous and can be life-threatening. Complications include encephalitis and blindness. Recently, HSV-1 infections have been associated with the development of Alzheimer's Disease. To date, no effective vaccines against HSV-1 are on the market. Pseudorabies virus (PRV) and bovine herpesvirus type 1 (BoHV-1) are two alphaherpesviruses of major veterinary importance. Although efforts have been made to eradicate these viruses from livestock animals, clinical problems still occur, resulting in great economic losses for farmers. It is evident that new insights into the pathogenesis of alphaherpesviruses are needed, to develop effective treatme","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0187324"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11558996/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142391685","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 riboflavin biosynthetic pathway as a novel target for antifungal drugs against <i>Candida</i> species.","authors":"Jana Nysten, Arne Peetermans, Dries Vaneynde, Stef Jacobs, Liesbeth Demuyser, Patrick Van Dijck","doi":"10.1128/mbio.02502-24","DOIUrl":"10.1128/mbio.02502-24","url":null,"abstract":"<p><p>In recent decades, there has been an increase in the occurrence of fungal infections; yet, the arsenal of drugs available to fight invasive infections remains very limited. The development of new antifungal agents is hindered by the restricted number of molecular targets that can be exploited, given the shared eukaryotic nature of fungi and their hosts which often leads to host toxicity. In this paper, we examine the riboflavin biosynthetic pathway as a potential novel drug target. Riboflavin is an essential nutrient for all living organisms. Its biosynthetic pathway does not exist in humans, who obtain riboflavin through their diet. Our findings demonstrate that all enzymes in the pathway are essential for <i>Candida albicans</i>, <i>Candida glabrata,</i> and <i>Saccharomyces cerevisiae.</i> Auxotrophic strains, which mimic a drug targeting the biosynthesis pathway, experience rapid mortality in the absence of supplemented riboflavin. Furthermore, <i>RIB1</i> is essential for virulence in both <i>C. albicans</i> and <i>C. glabrata</i> in a systemic mouse model. The fungal burden of a <i>RIB1</i> deletion strain is significantly reduced in the kidneys and brain of infected mice, and this reduction becomes more pronounced over time. Nevertheless, auxotrophic cells can still take up external riboflavin when supplemented. We identified Orf19.4337 as the riboflavin importer in <i>C. albicans</i> and named it Rut1. We found that Rut1 only facilitates growth at external riboflavin concentrations that exceed the physiological concentrations in the human body. This suggests that riboflavin uptake is unlikely to serve as a resistance mechanism against drugs targeting the biosynthesis pathway. Interestingly, the uptake system in <i>S. cerevisiae</i> is more effective than in <i>C. albicans</i> and <i>C. glabrata,</i> enabling an auxotrophic <i>S. cerevisiae</i> strain to outcompete an auxotrophic <i>C. albicans</i> strain in lower riboflavin concentrations.</p><p><strong>Importance: </strong><i>Candida</i> species are a common cause of invasive fungal infections. <i>Candida albicans</i>, in particular, poses a significant threat to immunocompromised individuals. This opportunistic pathogen typically lives as a commensal on mucosal surfaces of healthy individuals but it can also cause invasive infections associated with high morbidity and mortality. Currently, there are only three major classes of antifungal drugs available to treat these infections. In addition, the efficacy of these antifungal agents is restricted by host toxicity, suboptimal pharmacokinetics, a narrow spectrum of activity, intrinsic resistance of fungal species, such as <i>Candida glabrata</i>, to certain drugs, and the acquisition of resistance over time. Therefore, it is crucial to identify new antifungal drug targets with novel modes of action to add to the limited armamentarium.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0250224"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559065/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142469446","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":"Role of VapBC4 toxin-antitoxin system of <i>Sulfolobus acidocaldarius</i> in heat stress adaptation.","authors":"Arghya Bhowmick, Alejandra Recalde, Chandrima Bhattacharyya, Ankita Banerjee, Jagriti Das, Ulises E Rodriguez-Cruz, Sonja-Verena Albers, Abhrajyoti Ghosh","doi":"10.1128/mbio.02753-24","DOIUrl":"https://doi.org/10.1128/mbio.02753-24","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Toxin-antitoxin (TA) systems are important for stress adaptation in prokaryotes, including persistence, antibiotic resistance, pathogenicity, and biofilm formation. Toxins can cause cell death, reversible growth stasis, and direct inhibition of crucial cellular processes through various mechanisms, while antitoxins neutralize the effects of toxins. In bacteria, these systems have been studied in detail, whereas their function in archaea remains elusive. During heat stress, the thermoacidophilic archaeon &lt;i&gt;Sulfolobus acidocaldarius&lt;/i&gt; exhibited an increase in the expression of several bicistronic type II &lt;i&gt;vapBC&lt;/i&gt; TA systems, with the highest expression observed in the &lt;i&gt;vapBC4&lt;/i&gt; system. In the current study, we performed a comprehensive biochemical characterization of the VapBC4 TA system, establishing it as a bonafide type II toxin-antitoxin system. The VapC4 toxin is shown to have high-temperature catalyzed RNase activity specific for mRNA and rRNA, while the VapB4 antitoxin inhibits the toxic activity of VapC4 by interacting with it. VapC4 toxin expression led to heat-induced persister-like cell formation, allowing the cell to cope with the stress. Furthermore, this study explored the impact of &lt;i&gt;vapBC4&lt;/i&gt; deletion on biofilm formation, whereby deletion of &lt;i&gt;vapC4&lt;/i&gt; led to increased biofilm formation, suggesting its role in regulating biofilm formation. Thus, during heat stress, the liberated VapC4 toxin in cells could potentially signal a preference for persister cell formation over biofilm growth. Thus, our findings shed light on the diverse roles of the VapC4 toxin in inhibiting translation, inducing persister cell formation, and regulating biofilm formation in &lt;i&gt;S. acidocaldarius&lt;/i&gt;, enhancing our understanding of TA systems in archaea.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Importance: &lt;/strong&gt;This research enhances our knowledge of toxin-antitoxin (TA) systems in archaea, specifically in the thermoacidophilic archaeon &lt;i&gt;Sulfolobus acidocaldarius&lt;/i&gt;. TA systems are widespread in both bacterial and archaeal genomes, indicating their evolutionary importance. However, their exact functions in archaeal cellular physiology are still not well understood. This study sheds light on the complex roles of TA systems and their critical involvement in archaeal stress adaptation, including persistence and biofilm formation. By focusing on &lt;i&gt;S. acidocaldarius&lt;/i&gt;, which lives in habitats with fluctuating temperatures that can reach up to 90°C, the study reveals the unique challenges and survival mechanisms of this organism. The detailed biochemical analysis of the VapBC4 TA system, and its crucial role during heat stress, provides insights into how extremophiles can survive in harsh conditions. The findings of this study show the various functions of the VapC4 toxin, including inhibiting translation, inducing persister-like cell formation, and regulating biofilm formation. This knowledge improves our understanding of TA systems in thermoacidophiles and ","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0275324"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142622348","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":"Phosphorylation of Ser711 residue in the hypervariable region of zoonotic genotype 3 hepatitis E virus is important for virus replication.","authors":"Bo Wang, Sakthivel Subramaniam, Debin Tian, Hassan M Mahsoub, C Lynn Heffron, Xiang-Jin Meng","doi":"10.1128/mbio.02635-24","DOIUrl":"10.1128/mbio.02635-24","url":null,"abstract":"<p><p>Hepatitis E virus (HEV) is distinct from other hepatotropic viruses because it is zoonotic. HEV-1 and HEV-2 exclusively infect humans, whereas HEV-3 and HEV-4 are zoonotic. However, the viral and/or host factors responsible for cross-species HEV transmission remain elusive. The hypervariable region (HVR) in HEV is extremely heterogenetic and is implicated in HEV adaptation. Here, we investigated the potential role of Serine phosphorylation in the HVR in HEV replication. We first analyzed HVR sequences across different HEV genotypes and identified a unique region at the N-terminus of the HVR, which is variable in the human-exclusive HEV genotypes but relatively conserved in zoonotic HEV genotypes. Using predictive tools, we identified four potential phosphorylation sites that are highly conserved in zoonotic HEV-3 and HEV-4 genomes but absent in human-exclusive HEV-1 strains. To explore the functional significance of these putative phosphorylation sites, we introduced mutations into the HEV-3 infectious clone and indicator replicon, replacing each Serine residue individually with alanine or aspartic acid, and assessed the impact of these substitutions on HEV-3 replication. We found that the phospho-blatant S711A mutant significantly reduced virus replication, whereas the phospho-mimetic S711D mutant modestly reduced virus replication. Conversely, mutations in the other three Serine residues did not significantly affect HEV-3 replication. Furthermore, we demonstrated that Ser711 phosphorylation did not alter host cell tropism of zoonotic HEV-3. In conclusion, our results showed that potential phosphorylation of the Ser711 residue significantly affects HEV-3 replication <i>in vitro</i>, providing new insights into the potential mechanisms of zoonotic HEV transmission.IMPORTANCEHEV is an important zoonotic pathogen, causing both acute and chronic hepatitis E and extrahepatic manifestation of diseases, such as neurological sequelae. The zoonotic HEV-3 is linked to chronic infection and neurological diseases. The specific viral and/or host factors facilitating cross-species HEV infection are unknown. The intrinsically disordered HVR in ORF1 is crucial for viral fitness and adaptation, both <i>in vitro</i> and <i>in vivo</i>. We hypothesized that phosphorylation of Serine residues in the HVR of zoonotic HEV by unknown host cellular kinases is associated with cross-species HEV transmission. In this study, we identified a conserved region within the HVR of zoonotic HEV strains but absent in the human-exclusive HEV-1 and HEV-2. We elucidated the important role of phosphorylation at the Ser711 residue in zoonotic HEV-3 replication, without altering the host cell tropism. These findings contribute to our understanding the mechanisms of cross-species HEV transmission.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0263524"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559016/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142391684","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>Cryptococcus neoformans</i> infections: aspartyl protease potential to improve outcome in susceptible hosts.","authors":"Frédérique Vernel-Pauillac, Christine Laurent-Winter, Laurence Fiette, Guilhem Janbon, Vishukumar Aimanianda, Françoise Dromer","doi":"10.1128/mbio.02733-24","DOIUrl":"10.1128/mbio.02733-24","url":null,"abstract":"<p><p>Though a confined or a broad population is exposed respectively to endemic or pandemic infections, in the same environment, some individuals resist the development of infections. The attributed reason is the inheritance of a set of immune system genes that can efficiently deal with the pathogens. In this study, we show how outbred mice differentially respond to <i>Cryptococcus neoformans,</i> a fungal pathogen, and the mechanism through which the surviving mice mount a protective immune defense. We identified that those mice developing antibodies specifically against Pep1p, an aspartic protease secreted by <i>C. neoformans</i>, had significantly improved survival. Vaccination (either prophylactic or therapeutic) with a recombinant Pep1p significantly increased the survival of the mice by decreasing the fungal load and stimulating a protective immune response. Passive immunization of <i>C. neoformans-</i>infected mice with monoclonal antibodies developed against Pep1p also improves the survival of the mice by increasing phagocytosis of <i>C. neoformans</i> and decreasing the multiplication of this fungus. Together, these data demonstrate the prophylactic and therapeutic potentials of the <i>C. neoformans</i> antigenic protein Pep1p or Pep1p-specific antibodies against this fungal infection. Also, this study suggests that the immunological interaction and thereby the responses developed against a pathogen guide the hosts to behave differentially against microbial pathogenicity.</p><p><strong>Importance: </strong>Vaccination and immunotherapies against fungal pathogens still remain a challenge. Here, we show using an <i>in vivo</i> model based on outbred mice that development of antibodies against Pep1p, an antigenic protein of the fungal pathogen <i>Cryptococcus neoformans</i>, confers resistance to this fungal infection. In support of this observation, prophylactic or therapeutic immunization of the mice with recombinant Pep1p could improve their survival when infected with a lethal dose of <i>C. neoformans</i>. Moreover, passive therapy with monoclonal anti-Pep1p antibodies also enhanced survival of the mice from <i>C. neoformans</i> infection. The associated antifungal mechanisms were mounting of a protective immune response and the development of fungal specific antibodies that decrease the fungal burden due to an increase in their phagocytosis and/or inhibit the fungal multiplication. Together, our study demonstrates (a) the mode of host-fungal interaction and the immune response developed thereby play a crucial role in developing resistance against <i>C. neoformans</i>; (b) Pep1p, an aspartic protease as well as an antigenic protein secreted by <i>C. neoformans</i>, can be exploited for vaccination (both prophylactic and therapeutic) or immunotherapy to improve the host defense during this fungal infection.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0273324"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11559057/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142503520","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":"Metal availability shapes early life microbial ecology and community succession.","authors":"Joshua Soto Ocaña, Elliot S Friedman, Orlaith Keenan, Nile U Bayard, Eileen Ford, Ceylan Tanes, Matthew J Munneke, William N Beavers, Eric P Skaar, Kyle Bittinger, Babette S Zemel, Gary D Wu, Joseph P Zackular","doi":"10.1128/mbio.01534-24","DOIUrl":"10.1128/mbio.01534-24","url":null,"abstract":"<p><p>The gut microbiota plays a critical role in human health and disease. Microbial community assembly and succession early in life are influenced by numerous factors. In turn, assembly of this microbial community is known to influence the host, including immune system development, and has been linked to outcomes later in life. To date, the role of host-mediated nutritional immunity and metal availability in shaping microbial community assembly and succession early in life has not been explored in depth. Using a human infant cohort, we show that the metal-chelating protein calprotectin is highly abundant in infants. Taxa previously shown to be successful early colonizers of the infant gut, such as <i>Enterococcus</i>, <i>Enterobacteriaceae,</i> and <i>Bacteroides,</i> are highly resistant to experimental metal starvation in culture. <i>Lactobacillus</i>, meanwhile, is highly susceptible to metal restriction, pointing to a possible mechanism by which host-mediated metal limitation shapes the fitness of early colonizing taxa in the infant gut. We further demonstrate that formula-fed infants harbor markedly higher levels of metals in their gastrointestinal tract compared to breastfed infants. Formula-fed infants with high levels of metals harbor distinct microbial communities compared to breastfed infants, with higher levels of <i>Enterococcus</i>, <i>Enterobacter,</i> and <i>Klebsiella</i>, taxa which show increased resistance to the toxic effects of high metal concentrations. These data highlight a new paradigm in microbial community assembly and suggest an unappreciated role for nutritional immunity and dietary metals in shaping the earliest colonization events of the microbiota.IMPORTANCEEarly life represents a critical window for microbial colonization of the human gastrointestinal tract. Surprisingly, we still know little about the rules that govern the successful colonization of infants and the factors that shape the success of early life microbial colonizers. In this study, we report that metal availability is an important factor in the assembly and succession of the early life microbiota. We show that the host-derived metal-chelating protein, calprotectin, is highly abundant in infants and successful early life colonizers can overcome metal restriction. We further demonstrate that feeding modality (breastmilk vs formula) markedly impacts metal levels in the gut, potentially influencing microbial community succession. Our work suggests that metals, a previously unexplored aspect of early life ecology, may play a critical role in shaping the early events of microbiota assembly in infants.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0153424"},"PeriodicalIF":5.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11558993/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142503526","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":"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}