RESUMEN
The understanding of how central metabolism and fermentation pathways regulate antimicrobial susceptibility in the anaerobic pathogen Bacteroides fragilis is still incomplete. Our study reveals that B. fragilis encodes two iron-dependent, redox-sensitive regulatory pirin protein genes, pir1 and pir2. The mRNA expression of these genes increases when exposed to oxygen and during growth in iron-limiting conditions. These proteins, Pir1 and Pir2, influence the production of short-chain fatty acids and modify the susceptibility to metronidazole and amixicile, a new inhibitor of pyruvate: ferredoxin oxidoreductase in anaerobes. We have demonstrated that Pir1 and Pir2 interact directly with this oxidoreductase, as confirmed by two-hybrid system assays. Furthermore, structural analysis using AlphaFold2 predicts that Pir1 and Pir2 interact stably with several central metabolism enzymes, including the 2-ketoglutarate:ferredoxin oxidoreductases Kor1AB and Kor2CDAEBG. We used a series of metabolic mutants and electron transport chain inhibitors to demonstrate the extensive impact of bacterial metabolism on metronidazole and amixicile susceptibility. We also show that amixicile is an effective antimicrobial against B. fragilis in an experimental model of intra-abdominal infection. Our investigation led to the discovery that the kor2AEBG genes are essential for growth and have dual functions, including the formation of 2-ketoglutarate via the reverse TCA cycle. However, the metabolic activity that bypasses the function of Kor2AEBG following the addition of phospholipids or fatty acids remains undefined. Overall, our study provides new insights into the central metabolism of B. fragilis and its regulation by pirin proteins, which could be exploited for the development of new narrow-spectrum antimicrobials in the future.
Asunto(s)
Antibacterianos , Bacteroides fragilis , Metronidazol , Bacteroides fragilis/genética , Bacteroides fragilis/efectos de los fármacos , Bacteroides fragilis/enzimología , Bacteroides fragilis/metabolismo , Metronidazol/farmacología , Metronidazol/metabolismo , Antibacterianos/farmacología , Antibacterianos/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Pruebas de Sensibilidad Microbiana , Regulación Bacteriana de la Expresión GénicaRESUMEN
Necrotizing enterocolitis (NEC) is a leading cause of morbidity and mortality in premature infants with no specific treatments available. We aimed to identify the molecular mechanisms underlying NEC and investigate the therapeutic effects of Bacteroides fragilis on NEC. Clinical samples of infant feces, bile acid-targeted metabolomics, pathological staining, bioinformatics analysis, NEC rat model, and co-immunoprecipitation were used to explore the pathogenesis of NEC. Taxonomic characterization of the bile salt hydrolase (bsh) gene, enzyme activity assays, 16S rRNA sequencing, and organoids were used to explore the therapeutic effects of B. fragilis on NEC-related intestinal damage. Clinical samples, NEC rat models, and in vitro experiments revealed that total bile acid increased in the blood but decreased in feces. Moreover, the levels of FXR and other bile acid metabolism-related genes were abnormal, resulting in disordered bile acid metabolism in NEC. Taurochenodeoxycholic acid accelerated NEC pathogenesis and taurodeoxycholate alleviated NEC. B. fragilis displayed bsh genes and enzyme activity and alleviated intestinal damage by restoring gut microbiota dysbiosis and bile acid metabolism abnormalities by inhibiting the FXR-NLRP3 signaling pathway. Our results provide valuable insights into the therapeutic role of B. fragilis in NEC. Administering B. fragilis may substantially alleviate intestinal damage in NEC.
Asunto(s)
Amidohidrolasas , Bacteroides fragilis , Ácidos y Sales Biliares , Enterocolitis Necrotizante , Microbioma Gastrointestinal , Proteína con Dominio Pirina 3 de la Familia NLR , Receptores Citoplasmáticos y Nucleares , Transducción de Señal , Enterocolitis Necrotizante/metabolismo , Enterocolitis Necrotizante/microbiología , Enterocolitis Necrotizante/tratamiento farmacológico , Animales , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Proteína con Dominio Pirina 3 de la Familia NLR/genética , Bacteroides fragilis/metabolismo , Bacteroides fragilis/genética , Transducción de Señal/efectos de los fármacos , Ácidos y Sales Biliares/metabolismo , Ratas , Receptores Citoplasmáticos y Nucleares/metabolismo , Receptores Citoplasmáticos y Nucleares/genética , Microbioma Gastrointestinal/efectos de los fármacos , Amidohidrolasas/metabolismo , Amidohidrolasas/genética , Humanos , Ratas Sprague-Dawley , Recién Nacido , Modelos Animales de Enfermedad , Masculino , Femenino , Probióticos/administración & dosificación , Probióticos/farmacología , Recien Nacido Prematuro , Disbiosis/microbiologíaRESUMEN
The human intestinal mucus layer protects against pathogenic microorganisms and harmful substances, whereas it also provides an important colonization niche for mutualistic microbes. The main functional components of mucus are heavily glycosylated proteins, called mucins. Mucins can be cleaved and utilized by intestinal microbes. The mechanisms between intestinal microbes and the regulation of mucin glycosylation are still poorly understood. In this study, in vitro mucus was produced by HT29-MTX-E12 cells under Semi-Wet interface with Mechanical Stimulation. Cells were exposed to pasteurized nonpathogenic bacteria Akkermansia muciniphila, Ruminococcus gnavus, and Bacteroides fragilis to evaluate influence on glycosylation patterns. Following an optimized protocol, O- and N-glycans were efficiently and reproducibly released, identified, and semiquantified using MALDI-TOF-MS and PGC-LC-MS/MS. Exposure of cells to bacteria demonstrated increased diversity of sialylated O-glycans and increased abundance of high mannose N-glycans in in vitro produced mucus. Furthermore, changes in glycan ratios were observed. It is speculated that bacterial components interact with the enzymatic processes in glycan production and that pasteurized bacteria influence glycosyltransferases or genes involved. These results highlight the influence of pasteurized bacteria on glycosylation patterns, stress the intrinsic relationship between glycosylation and microbiota, and show the potential of using in vitro produced mucus to study glycosylation behavior.
Asunto(s)
Microbioma Gastrointestinal , Moco , Polisacáridos , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Espectrometría de Masas en Tándem , Glicosilación , Humanos , Espectrometría de Masas en Tándem/métodos , Moco/microbiología , Moco/metabolismo , Moco/química , Polisacáridos/metabolismo , Polisacáridos/química , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos , Mucinas/metabolismo , Mucosa Intestinal/metabolismo , Mucosa Intestinal/microbiología , Bacterias/metabolismo , Bacterias/clasificación , Bacterias/genética , Células HT29 , Cromatografía Liquida/métodos , Bacteroides fragilis/metabolismo , Bacteroides fragilis/química , Bacteroides fragilis/fisiología , Pasteurización , Akkermansia/metabolismo , Cromatografía Líquida con Espectrometría de MasasRESUMEN
The gut microbiota and microglia play critical roles in Alzheimer's disease (AD), and elevated Bacteroides is correlated with cerebrospinal fluid amyloid-ß (Aß) and tau levels in AD. We hypothesize that Bacteroides contributes to AD by modulating microglia. Here we show that administering Bacteroides fragilis to APP/PS1-21 mice increases Aß plaques in females, modulates cortical amyloid processing gene expression, and down regulates phagocytosis and protein degradation microglial gene expression. We further show that administering Bacteroides fragilis to aged wild-type male and female mice suppresses microglial uptake of Aß1-42 injected into the hippocampus. Depleting murine Bacteroidota with metronidazole decreases amyloid load in aged 5xFAD mice, and activates microglial pathways related to phagocytosis, cytokine signaling, and lysosomal degradation. Taken together, our study demonstrates that members of the Bacteroidota phylum contribute to AD pathogenesis by suppressing microglia phagocytic function, which leads to impaired Aß clearance and accumulation of amyloid plaques.
Asunto(s)
Enfermedad de Alzheimer , Péptidos beta-Amiloides , Modelos Animales de Enfermedad , Ratones Transgénicos , Microglía , Fagocitosis , Placa Amiloide , Animales , Microglía/metabolismo , Microglía/efectos de los fármacos , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/microbiología , Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides/metabolismo , Placa Amiloide/metabolismo , Femenino , Ratones , Masculino , Bacteroides fragilis/metabolismo , Microbioma Gastrointestinal , Humanos , Ratones Endogámicos C57BL , Hipocampo/metabolismo , Hipocampo/patologíaRESUMEN
A role for vitamin D in immune modulation and in cancer has been suggested. In this work, we report that mice with increased availability of vitamin D display greater immune-dependent resistance to transplantable cancers and augmented responses to checkpoint blockade immunotherapies. Similarly, in humans, vitamin D-induced genes correlate with improved responses to immune checkpoint inhibitor treatment as well as with immunity to cancer and increased overall survival. In mice, resistance is attributable to the activity of vitamin D on intestinal epithelial cells, which alters microbiome composition in favor of Bacteroides fragilis, which positively regulates cancer immunity. Our findings indicate a previously unappreciated connection between vitamin D, microbial commensal communities, and immune responses to cancer. Collectively, they highlight vitamin D levels as a potential determinant of cancer immunity and immunotherapy success.
Asunto(s)
Bacteroides fragilis , Microbioma Gastrointestinal , Inhibidores de Puntos de Control Inmunológico , Neoplasias , Vitamina D , Animales , Femenino , Humanos , Masculino , Ratones , Bacteroides fragilis/metabolismo , Microbioma Gastrointestinal/efectos de los fármacos , Inhibidores de Puntos de Control Inmunológico/uso terapéutico , Inhibidores de Puntos de Control Inmunológico/farmacología , Inmunoterapia , Mucosa Intestinal/inmunología , Mucosa Intestinal/microbiología , Mucosa Intestinal/metabolismo , Ratones Endogámicos C57BL , Neoplasias/inmunología , Neoplasias/microbiología , Neoplasias/terapia , Vitamina D/administración & dosificación , Vitamina D/metabolismo , Dieta , Línea Celular Tumoral , Calcifediol/administración & dosificación , Calcifediol/metabolismo , Proteína de Unión a Vitamina D/genética , Proteína de Unión a Vitamina D/metabolismoRESUMEN
Vitamin D modulates intestinal epithelial cell function to enhance antitumor microbes.
Asunto(s)
Bacteroides fragilis , Microbioma Gastrointestinal , Inhibidores de Puntos de Control Inmunológico , Inmunoterapia , Neoplasias , Vitamina D , Animales , Humanos , Ratones , Mucosa Intestinal/inmunología , Mucosa Intestinal/metabolismo , Mucosa Intestinal/microbiología , Neoplasias/inmunología , Neoplasias/microbiología , Neoplasias/terapia , Vitamina D/administración & dosificación , Vitamina D/metabolismo , Inhibidores de Puntos de Control Inmunológico/uso terapéutico , Bacteroides fragilis/metabolismoRESUMEN
Tumor-resident microbiota in breast cancer promotes cancer initiation and malignant progression. However, targeting microbiota to improve the effects of breast cancer therapy has not been investigated in detail. Here, we evaluated the microbiota composition of breast tumors and found that enterotoxigenic Bacteroides fragilis (ETBF) was highly enriched in the tumors of patients who did not respond to taxane-based neoadjuvant chemotherapy. ETBF, albeit at low biomass, secreted the toxic protein BFT-1 to promote breast cancer cell stemness and chemoresistance. Mechanistic studies showed that BFT-1 directly bound to NOD1 and stabilized NOD1 protein. NOD1 was highly expressed on ALDH+ breast cancer stem cells (BCSCs) and cooperated with GAK to phosphorylate NUMB and promote its lysosomal degradation, thereby activating the NOTCH1-HEY1 signaling pathway to increase BCSCs. NOD1 inhibition and ETBF clearance increase the chemosensitivity of breast cancer by impairing BCSCs.
Asunto(s)
Bacteroides fragilis , Neoplasias de la Mama , Resistencia a Antineoplásicos , Células Madre Neoplásicas , Proteína Adaptadora de Señalización NOD1 , Humanos , Proteína Adaptadora de Señalización NOD1/metabolismo , Proteína Adaptadora de Señalización NOD1/genética , Neoplasias de la Mama/patología , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/microbiología , Neoplasias de la Mama/genética , Femenino , Bacteroides fragilis/metabolismo , Bacteroides fragilis/genética , Células Madre Neoplásicas/metabolismo , Células Madre Neoplásicas/patología , Toxinas Bacterianas/metabolismo , Toxinas Bacterianas/genética , Animales , Ratones , Línea Celular Tumoral , MetaloendopeptidasasRESUMEN
Bacteria in the gastrointestinal tract produce amino acid bile acid amidates that can affect host-mediated metabolic processes1-6; however, the bacterial gene(s) responsible for their production remain unknown. Herein, we report that bile salt hydrolase (BSH) possesses dual functions in bile acid metabolism. Specifically, we identified a previously unknown role for BSH as an amine N-acyltransferase that conjugates amines to bile acids, thus forming bacterial bile acid amidates (BBAAs). To characterize this amine N-acyltransferase BSH activity, we used pharmacological inhibition of BSH, heterologous expression of bsh and mutants in Escherichia coli and bsh knockout and complementation in Bacteroides fragilis to demonstrate that BSH generates BBAAs. We further show in a human infant cohort that BBAA production is positively correlated with the colonization of bsh-expressing bacteria. Lastly, we report that in cell culture models, BBAAs activate host ligand-activated transcription factors including the pregnane X receptor and the aryl hydrocarbon receptor. These findings enhance our understanding of how gut bacteria, through the promiscuous actions of BSH, have a significant role in regulating the bile acid metabolic network.
Asunto(s)
Aciltransferasas , Amidohidrolasas , Aminas , Ácidos y Sales Biliares , Biocatálisis , Microbioma Gastrointestinal , Humanos , Aciltransferasas/metabolismo , Amidohidrolasas/metabolismo , Aminas/química , Aminas/metabolismo , Bacteroides fragilis/enzimología , Bacteroides fragilis/genética , Bacteroides fragilis/metabolismo , Ácidos y Sales Biliares/química , Ácidos y Sales Biliares/metabolismo , Estudios de Cohortes , Escherichia coli/enzimología , Escherichia coli/genética , Escherichia coli/metabolismo , Microbioma Gastrointestinal/fisiología , Ligandos , Receptor X de Pregnano/metabolismo , Receptores de Hidrocarburo de Aril/metabolismo , Factores de Transcripción/metabolismo , Lactante , Técnicas de Cultivo de CélulaRESUMEN
BACKGROUND: Deficient DNA mismatch repair (MMR) can cause microsatellite instability (MSI) and is more common in colorectal cancer (CRC) patients. Understanding the carcinogenic mechanism of bacteria and their impact on cancer cells is crucial. Bacteroides fragilis (B. fragilis) has been identified as a potential promoter of tumorigenesis through the alteration of signaling pathways. This study aims to assess the expression levels of msh2, msh6, mlh1, and the relative frequency of B. fragilis in biopsy samples from CRC patients. MATERIALS AND METHODS: Based on the sequence of mlh1, msh2, and msh6 genes, B. fragilis specific 16srRNA and bacterial universal 16srRNA specific primers were selected, and the expression levels of the target genes were analyzed using the Real-Time PCR method. RESULTS: Significant increases in the expression levels of mlh1, msh2, and msh6 genes were observed in the cancer group. Additionally, the expression of these MMR genes showed a significant elevation in samples positive for B. fragilis presence. The relative frequency of B. fragilis in the cancer group demonstrated a significant rise compared to the control group. CONCLUSION: The findings suggest a potential correlation between the abundance of B. fragilis and alterations in the expression of MMR genes. Since these genes can play a role in modifying colon cancer, investigating microbial characteristics and gene expression changes in CRC could offer a viable solution for CRC diagnosis.
Asunto(s)
Neoplasias Colorrectales Hereditarias sin Poliposis , Neoplasias Colorrectales , Humanos , Reparación de la Incompatibilidad de ADN/genética , Neoplasias Colorrectales/patología , Neoplasias Colorrectales Hereditarias sin Poliposis/diagnóstico , Neoplasias Colorrectales Hereditarias sin Poliposis/genética , Neoplasias Colorrectales Hereditarias sin Poliposis/patología , Bacteroides fragilis/genética , Bacteroides fragilis/metabolismo , Irán , Proteína 2 Homóloga a MutS/genética , Proteína 2 Homóloga a MutS/metabolismo , Inestabilidad de Microsatélites , Proteínas de Unión al ADN/genética , Homólogo 1 de la Proteína MutL/genética , Homólogo 1 de la Proteína MutL/metabolismo , BiopsiaRESUMEN
Our previous findings confirmed the high enrichment of Bacteroides fragilis (BF) in fecal samples from patients with colorectal cancer (CRC). The intestinal mucosal barrier is the first defense of the organism against commensal flora and intestinal pathogens and is closely associated with the occurrence and development of CRC. Therefore, this study aimed to investigate the molecular mechanisms through which BF mediates intestinal barrier injury and CRC progression. SW480 cells and a Caco2 intestinal barrier model were treated with entero-toxigenic BF (ETBF), its enterotoxin (B. fragilis toxin, BFT), and non-toxigenic BF (NTBF). Cell counting kit-8, flow cytometry, wound healing and transwell assays were performed to analyze the proliferation, apoptosis, migration, and invasion of SW480 cells. Transmission electron microscopy, FITC-dextran, and transepithelial electrical resistance (TEER) were used to analyze damage in the Caco2 intestinal barrier model. The Azoxymethane/Dextran Sulfate Sodium (AOM/DSS) animal model was established to evaluate the effect of ETBF on intestinal barrier injury and CRC progression in vivo. ETBF and BFT enhanced the viability, wound healing ratio, invasion, and EMT of SW480 cells. In addition, ETBF and BFT disrupted the tight junctions and villus structure in the intestinal barrier model, resulting in increased permeability and reduced TEER. Similarly, the expression of intestinal barrier-related proteins (MUC2, Occludin and Zo-1) was restricted by ETBF and BFT. Interestingly, the STAT3/ZEB2 axis was activated by ETBF and BFT, and treatment with Brevilin A (a STAT3 inhibitor) or knockdown of ZEB2 limited the promotional effect of ETBF and BFT on the SW480 malignant phenotype. In vivo experiments also confirmed that ETBF colonization accelerated tumor load, carcinogenesis, and intestinal mucosal barrier damage in the colorectum of the AOM/DSS animal model, and that treatment with Brevilin A alleviated these processes. ETBF-secreted BFT accelerated intestinal barrier damage and CRC by activating the STAT3/ZEB2 axis. Our findings provide new insights and perspectives for the application of ETBF in CRC treatment.
Asunto(s)
Toxinas Bacterianas , Bacteroides fragilis , Neoplasias Colorrectales , Factor de Transcripción STAT3 , Caja Homeótica 2 de Unión a E-Box con Dedos de Zinc , Animales , Humanos , Toxinas Bacterianas/genética , Toxinas Bacterianas/metabolismo , Bacteroides fragilis/genética , Bacteroides fragilis/metabolismo , Infecciones por Bacteroides/patología , Células CACO-2 , Neoplasias Colorrectales/patología , Crotonatos , Sesquiterpenos , Factor de Transcripción STAT3/metabolismo , Caja Homeótica 2 de Unión a E-Box con Dedos de Zinc/metabolismoRESUMEN
IMPORTANCE: The Gram-negative bacterium Bacteroides fragilis is a common member of the human gut microbiota that colonizes multiple host niches and can influence human physiology through a variety of mechanisms. Identification of genes that enable B. fragilis to grow across a range of host environments has been impeded in part by the relatively limited genetic tractability of this species. We have developed a high-throughput genetic resource for a B. fragilis strain isolated from a UC pouchitis patient. Bile acids limit microbial growth and are altered in abundance in UC pouches, where B. fragilis often blooms. Using this resource, we uncovered pathways and processes that impact B. fragilis fitness in bile and that may contribute to population expansions during bouts of gut inflammation.
Asunto(s)
Bacteroides fragilis , Reservoritis , Humanos , Bacteroides fragilis/metabolismo , Ácidos y Sales Biliares/metabolismo , Inflamación , BilisRESUMEN
Bacteroides fragilis is a universal member of the dominant commensal gut phylum Bacteroidetes. Its fermentation products and abundance have been linked to obesity, inflammatory bowel disease, and other disorders through its effects on host metabolic regulation and the immune system. As of yet, there has been no curated systems-level characterization of B. fragilis' metabolism that provides a comprehensive analysis of the link between human diet and B. fragilis' metabolic products. To address this, we developed a genome-scale metabolic model of B. fragilis strain 638R. The model iMN674 contains 1,634 reactions, 1,362 metabolites, three compartments, and reflects the strain's ability to utilize 142 metabolites. Predictions made with this model include its growth rate and efficiency on these substrates, the amounts of each fermentation product it produces under different conditions, and gene essentiality for each biomass component. The model highlights and resolves gaps in knowledge of B. fragilis' carbohydrate metabolism and its corresponding transport proteins. This high quality model provides the basis for rational prediction of B. fragilis' metabolic interactions with its environment and its host.
Asunto(s)
Bacteroides fragilis , Proteínas Portadoras , Humanos , Bacteroides fragilis/genética , Bacteroides fragilis/metabolismo , Proteínas Portadoras/metabolismoRESUMEN
Oral and gut microbiomes are important for the maintenance of homeostasis in the human body. Altered or disturbed mutualism between their members results in dysbiosis with local injury and subsequent systemic diseases. The high bacterial density causes intense competition among microbiome residents to acquire nutrients, including iron and heme, the latter of high importance for heme auxotrophic members of the Bacteroidetes phylum. Our main hypothesis is that the heme acquisition mechanism, with the leading role played by a novel HmuY family of hemophore-like proteins, can be used to fulfill nutritional requirements and increase virulence. We characterized HmuY homologs expressed by Bacteroides fragilis and compared their properties with the first representative of this family, the HmuY protein of Porphyromonas gingivalis. In contrast to other Bacteroidetes members, B. fragilis produces three HmuY homologs (Bfr proteins). All bfr transcripts were produced at higher levels in bacteria starved of iron and heme (fold change increase ~60, ~90, and ~70 for bfrA, bfrB, and bfrC, respectively). X-ray protein crystallography showed that B. fragilis Bfr proteins are structurally similar to P. gingivalis HmuY and to other homologs, except for differences in the potential heme-binding pockets. BfrA binds heme, mesoheme, and deuteroheme, but preferentially under reducing conditions, using Met175 and Met146 to coordinate heme iron. BfrB binds iron-free protoporphyrin IX and coproporphyrin III, whereas BfrC does not bind porphyrins. HmuY is capable of heme sequestration from BfrA, which might increase the ability of P. gingivalis to cause dysbiosis also in the gut microbiome.
Asunto(s)
Microbioma Gastrointestinal , Porphyromonas gingivalis , Humanos , Bacteroides fragilis/genética , Bacteroides fragilis/metabolismo , Disbiosis , Hemo/metabolismo , Proteínas Bacterianas/metabolismoRESUMEN
Bacteroides species can use fumarate and oxygen as terminal electron acceptors during cellular respiration. In the human gut, oxygen diffuses from intestinal epithelial cells supplying "nanaerobic" oxygen levels. Many components of the anaerobic respiratory pathway have been determined, but such analyses have not been performed for nanaerobic respiration. Here, we present genetic, biochemical, enzymatic, and mass spectrometry analyses to elucidate the nanaerobic respiratory pathway in Bacteroides fragilis. Under anaerobic conditions, the transfer of electrons from NADH to the quinone pool has been shown to be contributed by two enzymes, NQR and NDH2. We find that the activity contributed by each under nanaerobic conditions is 77 and 23%, respectively, similar to the activity levels under anaerobic conditions. Using mass spectrometry, we show that the quinone pool also does not differ under these two conditions and consists of a mixture of menaquinone-8 to menaquinone-11, with menaquinone-10 predominant under both conditions. Analysis of fumarate reductase showed that it is synthesized and active under anaerobic and nanaerobic conditions. Previous RNA sequencing data and new transcription reporter assays show that expression of the cytochrome bd oxidase gene does not change under these conditions. Under nanaerobic conditions, we find both increased CydA protein and increased cytochrome bd activity. Reduced-minus-oxidized spectra of membranes showed the presence of heme d when the bacteria were grown in the presence of protoporphyrin IX and iron under both anaerobic and nanaerobic conditions, suggesting that the active oxidase can be assembled with or without oxygen. IMPORTANCE By performing a comprehensive analysis of nanaerobic respiration in Bacteroides fragilis, we show that this organism maintains capabilities for anaerobic respiration on fumarate and nanaerobic respiration on oxygen simultaneously. The contribution of the two NADH:quinone oxidoreductases and the composition of the quinone pool are the same under both conditions. Fumarate reductase and cytochrome bd are both present, and which of these terminal enzymes is active in electron transfer depends on the availability of the final electron acceptor: fumarate or oxygen. The synthesis of cytochrome bd and fumarate reductase under both conditions serves as an adaptation to an environment with low oxygen concentrations so that the bacteria can maximize energy conservation during fluctuating environmental conditions or occupation of different spatial niches.
Asunto(s)
Bacteroides fragilis , Succinato Deshidrogenasa , Humanos , Bacteroides fragilis/genética , Bacteroides fragilis/metabolismo , Anaerobiosis , Succinato Deshidrogenasa/metabolismo , Vitamina K 2 , NAD/metabolismo , Transporte de Electrón , Citocromos/metabolismo , Quinonas/metabolismo , Respiración , Oxígeno/metabolismo , Fumaratos/metabolismoRESUMEN
Glycolipids are complex molecules involved in important cellular processes. Among them, the glycosphingolipid α-galactosylceramide has proven to be of interest in biomedicine for its immunostimulatory capabilities. Given its structural requirements, the use of ceramide glycosyltransferase enzymes capable of synthesizing this molecule under in vivo or in vitro conditions is a potential production strategy. Several GT4 enzymes from Bacteroides fragilis were considered as potential candidates in addition to the known BF9343_3149, but only this one showed glycolipid synthase activity. The enzyme was expressed as a SUMO fusion protein to produce soluble protein. It is a non-processive glycosyltransferase that prefers UDP-Gal over UDP-Glc as a donor substrate, and maximum activity was found at pH 7.3 and around 30-35 °C. It does not require metal cations for activity as other GT4 enzymes, but Zn2+ inactivates the enzyme. The reaction occurs when the ceramide lipid acceptor is solubilized with BSA (100% conversion) but not when it is presented in mixed micelles, and anionic lipids do not increase activity, as in other membrane-associated glycolipid synthases. Further protein engineering to increase stability and activity can make feasible the enzymatic synthesis of α-GalCer for biomedical applications.
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Infecciones Bacterianas , Glucolípidos , Humanos , Glucolípidos/química , Bacteroides fragilis/metabolismo , Glicosiltransferasas/metabolismo , Óxido Nítrico Sintasa , Ceramidas , Uridina DifosfatoRESUMEN
Bacteroides fragilis is an abundant commensal component of the healthy human colon. However, under dysbiotic conditions, enterotoxigenic B. fragilis (ETBF) may arise and elicit diarrhea, anaerobic bacteremia, inflammatory bowel disease, and colorectal cancer. Most worrisome, ETBF is resistant to many disparate antibiotics. ETBF's only recognized specific virulence factor is a zinc-dependent metallopeptidase (MP) called B. fragilis toxin (BFT) or fragilysin, which damages the intestinal mucosa and triggers disease-related signaling mechanisms. Thus, therapeutic targeting of BFT is expected to limit ETBF pathogenicity and improve the prognosis for patients. We focused on one of the naturally occurring BFT isoforms, BFT-3, and managed to repurpose several approved drugs as BFT-3 inhibitors through a combination of biophysical, biochemical, structural, and cellular techniques. In contrast to canonical MP inhibitors, which target the active site of mature enzymes, these effectors bind to a distal allosteric site in the proBFT-3 zymogen structure, which stabilizes a partially unstructured, zinc-free enzyme conformation by shifting a zinc-dependent disorder-to-order equilibrium. This yields proBTF-3 incompetent for autoactivation, thus ablating hydrolytic activity of the mature toxin. Additionally, a similar destabilizing effect is observed for the activated protease according to biophysical and biochemical data. Our strategy paves a novel way for the development of highly specific inhibitors of ETBF-mediated enteropathogenic conditions.
Asunto(s)
Infecciones Bacterianas , Toxinas Bacterianas , Antibacterianos/metabolismo , Toxinas Bacterianas/metabolismo , Bacteroides fragilis/metabolismo , Precursores Enzimáticos/metabolismo , Humanos , Metaloendopeptidasas/metabolismo , Factores de Virulencia/metabolismoRESUMEN
Enteric glial cells (EGCs) are involved in intestinal inflammation. In this study, we will investigate how Bifidobacterium bifidum (B.b.) and Bacteroides fragilis (B.f.) influence EGC regulation. After pretreatment with lipopolysaccharide (LPS) and interferon-γ (IFN-γ), the expressions of major histocompatibility complex class II (MHC-II), CD80, CD86, glial cell line-derived neurotrophic factor (GDNF), toll-like receptor 2 (TLR-2), and tumor necrosis factor-α (TNF-α) in EGCs were detected using polymerase chain reaction and western blot after co-culture with the supernatants of B.b. or B.f. (multiplicity of infection, 40:1 or 80:1). Finally, EGCs were co-cultured with naive CD4+ T cells, and the expressions of interleukin (IL)-2, IL-4, IL-10, and IL-17 in supernatant were measured using enzyme-linked immunosorbent assay (ELISA). The mRNA expressions of MHC-II and CD86 in EGCs were increased after combined stimulation with LPS and IFN-γ. The expressions of MHC-II, GDNF, TLR-2, and TNF-α were all significantly upregulated in stimulated EGCs. The B.b. supernatant downregulated the expressions of MHC-II, GDNF, TLR-2, and TNF-α in stimulated EGCs, whereas the B.f. supernatant upregulated TLR-2 expression and downregulated MHC-II expression. The expressions of IL-4, IL-2, and IL-17 after co-culture of naive CD4+ T cells and stimulated EGCs were significantly increased. The supernatant of B.b. or B.f. downregulated the expressions of these cytokines. The low-concentration B.b. supernatant upregulated IL-10 expression. Conclusions B.b. and B.f. may influence intestinal inflammation by regulating MHC-II, GDNF, TLR-2, and TNF-α expression in EGCs and IL-4, IL-2, IL-17, and IL-10 secretion.
Asunto(s)
Bacteroides fragilis , Bifidobacterium bifidum , Neuroglía , Humanos , Bacteroides fragilis/metabolismo , Bifidobacterium bifidum/metabolismo , Células Cultivadas , Factor Neurotrófico Derivado de la Línea Celular Glial/metabolismo , Inflamación/metabolismo , Interferón gamma/metabolismo , Interleucina-10/metabolismo , Interleucina-17/metabolismo , Interleucina-2 , Interleucina-4/metabolismo , Lipopolisacáridos , Neuroglía/metabolismo , Neuroglía/microbiología , Receptor Toll-Like 2/metabolismo , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
Enterotoxigenic Bacteroides fragilis (ETBF) is consistently found at higher frequency in individuals with sporadic and hereditary colorectal cancer (CRC) and induces tumorigenesis in several mouse models of CRC. However, whether specific mutations induced by ETBF lead to colon tumor formation has not been investigated. To determine if ETBF-induced mutations impact the Apc gene, and other tumor suppressors or proto-oncogenes, we performed whole-exome sequencing and whole-genome sequencing on tumors isolated after ETBF and sham colonization of Apcmin/+ and Apcmin/+Msh2fl/flVC mice, as well as whole-genome sequencing of organoids cocultured with ETBF. Our results indicate that ETBF-induced tumor formation results from loss of heterozygosity (LOH) of Apc, unless the mismatch repair system is disrupted, in which case, tumor formation results from new acquisition of protein-truncating mutations in Apc. In contrast to polyketide synthase-positive Escherichia coli (pks+ E. coli), ETBF does not produce a unique mutational signature; instead, ETBF-induced tumors arise from errors in DNA mismatch repair and homologous recombination DNA damage repair, established pathways of tumor formation in the colon, and the same genetic mechanism accounting for sham tumors in these mouse models. Our analysis informs how this procarcinogenic bacterium may promote tumor formation in individuals with inherited predispositions to CRC, such as Lynch syndrome or familial adenomatous polyposis (FAP). IMPORTANCE Many studies have shown that microbiome composition in both the mucosa and the stool differs in individuals with sporadic and hereditary colorectal cancer (CRC). Both human and mouse models have established a strong association between particular microbes and colon tumor induction. However, the genetic mechanisms underlying putative microbe-induced colon tumor formation are not well established. In this paper, we applied whole-exome sequencing and whole-genome sequencing to investigate the impact of ETBF-induced genetic changes on tumor formation. Additionally, we performed whole-genome sequencing of human colon organoids exposed to ETBF to validate the mutational patterns seen in our mouse models and begin to understand their relevance in human colon epithelial cells. The results of this study highlight the importance of ETBF colonization in the development of sporadic CRC and in individuals with hereditary tumor conditions, such as Lynch syndrome and familial adenomatous polyposis (FAP).
Asunto(s)
Poliposis Adenomatosa del Colon , Infecciones Bacterianas , Neoplasias del Colon , Neoplasias Colorrectales Hereditarias sin Poliposis , Neoplasias Colorrectales , Poliposis Adenomatosa del Colon/genética , Poliposis Adenomatosa del Colon/patología , Animales , Infecciones Bacterianas/patología , Bacteroides fragilis/genética , Bacteroides fragilis/metabolismo , Colon/microbiología , Neoplasias del Colon/genética , Neoplasias del Colon/microbiología , Neoplasias del Colon/patología , Neoplasias Colorrectales/microbiología , Neoplasias Colorrectales Hereditarias sin Poliposis/genética , Neoplasias Colorrectales Hereditarias sin Poliposis/patología , Modelos Animales de Enfermedad , Escherichia coli/genética , Genes APC , Ratones , MutaciónRESUMEN
Enterotoxigenic Bacteroides fragilis (ETBF) has received significant attention for a possible association with, or causal role in, colorectal cancer (CRC). The goal of this review was to assess the status of the published evidence supporting (i) the association between ETBF and CRC and (ii) the causal role of ETBF in CRC. PubMed and Scopus searches were performed in August 2021 to identify human, animal, and cell studies pertaining to the role of ETBF in CRC. Inclusion criteria included the use of cell lines, mice, exposure to BFT or ETBF, and detection of bft. Review studies were excluded, and studies were limited to the English language. Quality of study design and risk of bias analysis was performed on the cell, animal, and human studies using ToxRTools, SYRCLE, and NOS, respectively. Ninety-five eligible studies were identified, this included 22 human studies, 24 animal studies, 43 cell studies, and 6 studies that included both cells and mice studies. We found that a large majority of studies supported an association or causal role of ETBF in CRC, as well as high levels of study bias was detected in the in vitro and in vivo studies. The high-level heterogeneity in study design and reporting made it difficult to synthesize these findings into a unified conclusion, suggesting that the need for future studies that include improved mechanistic models, longitudinal in vitro and in vivo evidence, and appropriate control of confounding factors will be required to confirm whether ETBF has a direct role in CRC etiopathogenesis.
Asunto(s)
Toxinas Bacterianas , Infecciones por Bacteroides , Neoplasias Colorrectales , Animales , Humanos , Ratones , Toxinas Bacterianas/metabolismo , Toxinas Bacterianas/toxicidad , Bacteroides fragilis/metabolismo , Infecciones por Bacteroides/complicaciones , Infecciones por Bacteroides/diagnóstico , Infecciones por Bacteroides/patología , Neoplasias Colorrectales/patologíaRESUMEN
Bacteroides fragilis is an obligately anaerobic Gram-negative bacterium and a major colonizer of the human large colon where Bacteroides is a predominant genus. During the growth of an individual clonal population, an astonishing number of reversible DNA inversion events occur, driving within-strain diversity. Additionally, the B. fragilis pan-genome contains a large pool of diverse polysaccharide biosynthesis loci, DNA restriction/modification systems and polysaccharide utilization loci, which generates remarkable between-strain diversity. Diversity clearly contributes to the success of B. fragilis within its normal habitat of the gastrointestinal (GI) tract and during infection in the extra-intestinal host environment. Within the GI tract, B. fragilis is usually symbiotic, for example providing localized nutrients for the gut epithelium, but B. fragilis within the GI tract may not always be benign. Metalloprotease toxin production is strongly associated with colorectal cancer. B. fragilis is unique amongst bacteria; some strains export a protein >99â% structurally similar to human ubiquitin and antigenically cross-reactive, which suggests a link to autoimmune diseases. B. fragilis is not a primary invasive enteric pathogen; however, if colonic contents contaminate the extra-intestinal host environment, it successfully adapts to this new habitat and causes infection; classically peritoneal infection arising from rupture of an inflamed appendix or GI surgery, which if untreated, can progress to bacteraemia and death. In this review selected aspects of B. fragilis adaptation to the different habitats of the GI tract and the extra-intestinal host environment are considered, along with the considerable challenges faced when studying this highly variable bacterium.