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MBio Jun 2020is one of the most abundant gut symbiont species, whose contribution to host health through its ability to degrade dietary polysaccharides and mature the immune system...
is one of the most abundant gut symbiont species, whose contribution to host health through its ability to degrade dietary polysaccharides and mature the immune system is under intense scrutiny. In contrast, adhesion and biofilm formation, which are potentially involved in gut colonization and microbiota structure and stability, have hardly been investigated in this intestinal bacterium. To uncover biofilm-related functions, we performed a transposon mutagenesis in the poorly biofilm-forming reference strain VPI-5482 and showed that capsule 4, one of the eight capsules, hinders biofilm formation. We then showed that the production of capsules 1, 2, 3, 5, and 6 also inhibits biofilm formation and that decreased capsulation of the population correlated with increased biofilm formation, suggesting that capsules could be masking adhesive surface structures. In contrast, we showed that capsule 8 displayed intrinsic adhesive properties. Finally, we demonstrated that , the homolog of the glycosylation locus, competes with capsule production and impacts its adhesion capacity. This study therefore establishes capsule regulation as a major determinant of biofilm formation, providing new insights into how modulation of different surface structures affects biofilm formation. The human gut harbors a complex bacterial community that plays important roles in host health and disease, including nutrient acquisition, maturation of the immune system, and resistance to infections. The capacity to adhere to surfaces and form communities called biofilms is believed to be important for niche colonization and maintenance of gut bacteria. However, little is known about the adhesion capacity of most gut bacteria. In this study, we investigated biofilm formation in , one of the most abundant bacteria of the normal mammalian intestine. We identified that capsules, a group of eight surface-exposed polysaccharidic layers mediating important interactions with the gut environment, are also major determinants of biofilm formation that mask or unmask adhesion factors. Studying how regulates its adhesion properties will allow us to better understand the physiology and specific properties of this important gut symbiont within anaerobic biofilms.
Topics: Animals; Bacterial Adhesion; Bacterial Capsules; Bacteroides thetaiotaomicron; Biofilms; Gene Expression Regulation, Bacterial; Male; Mice; Mice, Inbred C3H; Mutagenesis; Polysaccharides, Bacterial; Specific Pathogen-Free Organisms
PubMed: 32576670
DOI: 10.1128/mBio.00729-20 -
Microbiology (Reading, England) Jul 2021Capsular polysaccharides (CPSs) protect bacteria from host and environmental factors. Many bacteria can express different CPSs and these CPSs are phase variable. For...
Capsular polysaccharides (CPSs) protect bacteria from host and environmental factors. Many bacteria can express different CPSs and these CPSs are phase variable. For example, ) is a prominent member of the human gut microbiome and expresses eight different capsular polysaccharides. Bacteria, including , have been shown to change their CPSs to adapt to various niches such as immune, bacteriophage, and antibiotic perturbations. However, there are limited tools to study CPSs and fundamental questions regarding phase variance, including if gut bacteria can express more than one capsule at the same time, remain unanswered. To better understand the roles of different CPSs, we generated a CPS1-specific antibody and a flow cytometry assay to detect CPS expression in individual bacteria in the gut microbiota. Using these novel tools, we report for the first time that bacteria can simultaneously express multiple CPSs. We also observed that nutrients such as glucose and salts had no effect on CPS expression. The ability to express multiple CPSs at the same time may provide bacteria with an adaptive advantage to thrive amid changing host and environmental conditions, especially in the intestine.
Topics: Bacterial Capsules; Bacteroides thetaiotaomicron; Gastrointestinal Microbiome; Humans; Polysaccharides, Bacterial
PubMed: 34224345
DOI: 10.1099/mic.0.001066 -
Applied and Environmental Microbiology May 2019Acylated amino acids function as important components of the cellular membrane in some bacteria. Biosynthesis is initiated by the -acylation of the amino acid, and this...
Acylated amino acids function as important components of the cellular membrane in some bacteria. Biosynthesis is initiated by the -acylation of the amino acid, and this is followed by subsequent -acylation of the acylated molecule, resulting in the production of the mature diacylated amino acid lipid. In this study, we use both genetics and liquid chromatography-mass spectrometry (LC-MS) to characterize the biosynthesis and function of a diacylated glycine lipid (GL) species produced in We, and others, have previously reported the identification of a gene, named in this study, that encodes an -acyltransferase activity responsible for the production of a monoacylated glycine called -acyl-3-hydroxy-palmitoyl glycine (or commendamide). In all of the genomes sequenced so far, the gene is located immediately downstream from a gene, named , that is also predicted to encode a protein with acyltransferase activity. We use LC-MS to show that the coexpression of and results in the production of GL in We constructed a deletion mutant of the gene in , and we confirm that is required for the production of GL in Moreover, we show that is important for the ability of to adapt to stress and colonize the mammalian gut. Therefore, this report describes the genetic requirements for the biosynthesis of GL, a diacylated amino acid species that contributes to fitness in the human gut bacterium The gut microbiome has an important role in both health and disease of the host. The mammalian gut microbiome is often dominated by bacteria from the , an order that includes and In this study, we have identified an acylated amino acid, called glycine lipid, produced by , a beneficial bacterium originally isolated from the human gut. In addition to identifying the genes required for the production of glycine lipids, we show that glycine lipids have an important role during the adaptation of to a number of environmental stresses, including exposure to either bile or air. We also show that glycine lipids are important for the normal colonization of the murine gut by This work identifies glycine lipids as an important fitness determinant in and therefore increases our understanding of the molecular mechanisms underpinning colonization of the mammalian gut by beneficial bacteria.
Topics: Animals; Bacteroides thetaiotaomicron; Female; Genetic Fitness; Germ-Free Life; Glycine; Lipid Metabolism; Lipids; Mice; Mice, Inbred C57BL
PubMed: 30367006
DOI: 10.1128/AEM.02157-18 -
Nature Jun 2023Bacteroidetes are abundant members of the human microbiota, utilizing a myriad of diet- and host-derived glycans in the distal gut. Glycan uptake across the bacterial...
Bacteroidetes are abundant members of the human microbiota, utilizing a myriad of diet- and host-derived glycans in the distal gut. Glycan uptake across the bacterial outer membrane of these bacteria is mediated by SusCD protein complexes, comprising a membrane-embedded barrel and a lipoprotein lid, which is thought to open and close to facilitate substrate binding and transport. However, surface-exposed glycan-binding proteins and glycoside hydrolases also play critical roles in the capture, processing and transport of large glycan chains. The interactions between these components in the outer membrane are poorly understood, despite being crucial for nutrient acquisition by our colonic microbiota. Here we show that for both the levan and dextran utilization systems of Bacteroides thetaiotaomicron, the additional outer membrane components assemble on the core SusCD transporter, forming stable glycan-utilizing machines that we term utilisomes. Single-particle cryogenic electron microscopy structures in the absence and presence of substrate reveal concerted conformational changes that demonstrate the mechanism of substrate capture, and rationalize the role of each component in the utilisome.
Topics: Humans; Bacterial Outer Membrane; Bacterial Outer Membrane Proteins; Bacteroides thetaiotaomicron; Gastrointestinal Tract; Glycoside Hydrolases; Polysaccharides
PubMed: 37286596
DOI: 10.1038/s41586-023-06146-w -
Molecular Microbiology Mar 2021The human gut microbiota endows the host with a wealth of metabolic functions central to health, one of which is the degradation and fermentation of complex... (Review)
Review
The human gut microbiota endows the host with a wealth of metabolic functions central to health, one of which is the degradation and fermentation of complex carbohydrates. The Bacteroidetes are one of the dominant bacterial phyla of this community and possess an expanded capacity for glycan utilization. This is mediated via the coordinated expression of discrete polysaccharide utilization loci (PUL) that invariantly encode a TonB-dependent transporter (SusC) that works with a glycan-capturing lipoprotein (SusD). More broadly within Gram-negative bacteria, TonB-dependent transporters (TBDTs) are deployed for the uptake of not only sugars, but also more often for essential nutrients such as iron and vitamins. Here, we provide a comprehensive look at the repertoire of TBDTs found in the model gut symbiont Bacteroides thetaiotaomicron and the range of predicted functional domains associated with these transporters and SusD proteins for the uptake of both glycans and other nutrients. This atlas of the B. thetaiotaomicron TBDTs reveals that there are at least three distinct subtypes of these transporters encoded within its genome that are presumably regulated in different ways to tune nutrient uptake.
Topics: Bacterial Proteins; Bacteroides thetaiotaomicron; Gastrointestinal Microbiome; Humans; Iron; Lipoproteins; Membrane Proteins; Membrane Transport Proteins; Protein Conformation; Protein Domains; Sugars; Vitamins
PubMed: 33448497
DOI: 10.1111/mmi.14683 -
Microorganisms Oct 2020The development of infant gut microbiota is strongly influenced by nutrition. Human milk oligosaccharides (HMOSs) in breast milk selectively promote the growth of...
The development of infant gut microbiota is strongly influenced by nutrition. Human milk oligosaccharides (HMOSs) in breast milk selectively promote the growth of glycan-degrading microbes, which lays the basis of the microbial network. In this study, we investigated the trophic interaction between and the butyrate-producing in the presence of early-life carbohydrates. Anaerobic bioreactors were set up to study the monocultures of and the co-cultures of with in minimal media supplemented with lactose or a total human milk carbohydrate fraction. Bacterial growth (qPCR), metabolites (HPLC), and HMOS utilization (LC-ESI-MS) were monitored. displayed potent glycan catabolic capability with differential preference in degrading specific low molecular weight HMOSs, including the neutral trioses (2'-FL and 3-FL), neutral tetraoses (DFL, LNT, LNnT), neutral pentaoses (LNFP I, II, III, V), and acidic trioses (3'-SL and 6'-SL). In contrast, was not able to utilize lactose and HMOSs. However, the signature metabolite of , butyrate, was detected in co-culture with . As such, cross-fed on -derived monosaccharides, acetate, and d-lactate for growth and concomitant butyrate production. This study provides a proof of concept that could drive the butyrogenic metabolic network in the infant gut.
PubMed: 33019531
DOI: 10.3390/microorganisms8101513 -
Microbiology Spectrum Mar 2023Members of the phylum are abundant in healthy gastrointestinal (GI) tract flora. Bacteroides thetaiotaomicron is a commensal heme auxotroph and representative of this...
Members of the phylum are abundant in healthy gastrointestinal (GI) tract flora. Bacteroides thetaiotaomicron is a commensal heme auxotroph and representative of this group. are sensitive to host dietary iron restriction but proliferate in heme-rich environments that are also associated with colon cancer. We hypothesized that B. thetaiotaomicron may act as a host reservoir for iron and/or heme. In this study, we defined growth-promoting quantities of iron for B. thetaiotaomicron. B. thetaiotaomicron preferentially consumed and hyperaccumulated iron in the form of heme when presented both heme and nonheme iron sources in excess of its growth needs, leading to an estimated 3.6 to 8.4 mg iron in a model GI tract microbiome consisting solely of B. thetaiotaomicron. Protoporphyrin IX was identified as an organic coproduct of heme metabolism, consistent with anaerobic removal of iron from the heme leaving the intact tetrapyrrole as the observed product. Notably, no predicted or discernible pathway for protoporphyrin IX generation exists in B. thetaiotaomicron. Heme metabolism in congeners of B. thetaiotaomicron has previously been associated with the 6-gene operon, based on genetic studies. A bioinformatics survey demonstrated that the intact operon is widespread in but confined to members of the phylum and ubiquitous in healthy human GI tract flora. Anaerobic heme metabolism by commensal via is likely a major contributor to human host metabolism of the heme from dietary red meat and a driver for the selective growth of these species in the GI tract consortium. Research on bacterial iron metabolism has historically focused on the host-pathogen relationship, where the host suppresses pathogen growth by cutting off access to iron. Less is known about how host iron is shared with bacterial species that live commensally in the anaerobic human GI tract, typified by members of phylum . While many facultative pathogens avidly produce and consume heme iron, most GI tract anaerobes are heme auxotrophs whose metabolic preferences we aimed to describe. Understanding iron metabolism by model microbiome species like Bacteroides thetaiotaomicron is essential for modeling the ecology of the GI tract, which serves the long-term biomedical goals of manipulating the microbiome to facilitate host metabolism of iron and remediate dysbiosis and associated pathologies (e.g., inflammation and cancer).
PubMed: 36862015
DOI: 10.1128/spectrum.04815-22 -
Frontiers in Microbiology 2020Gram-negative bacteria ubiquitously produce and release nano-size, non-replicative outer membrane vesicles (OMVs). In the gastrointestinal (GI-) tract, OMVs generated by...
Gram-negative bacteria ubiquitously produce and release nano-size, non-replicative outer membrane vesicles (OMVs). In the gastrointestinal (GI-) tract, OMVs generated by members of the intestinal microbiota are believed to contribute to maintaining the intestinal microbial ecosystem and mediating bacteria-host interactions, including the delivery of bacterial effector molecules to host cells to modulate their physiology. Bacterial OMVs have also been found in the bloodstream although their origin and fate are unclear. Here we have investigated the interactions between OMVs produced by the major human gut commensal bacterium, (Bt), with cells of the GI-tract. Using a combination of culture systems including intestinal epithelial organoids and imaging we show that intestinal epithelial cells principally acquire Bt OMVs via dynamin-dependent endocytosis followed by intracellular trafficking to LAMP-1 expressing endo-lysosomal vesicles and co-localization with the perinuclear membrane. We observed that Bt OMVs can also transmigrate through epithelial cells via a paracellular route with imaging demonstrating that within hours of oral administration Bt OMVs can be detected in systemic tissues and in particular, the liver. Our findings raise the intriguing possibility that OMVs may act as a long-distance microbiota-host communication system.
PubMed: 32117106
DOI: 10.3389/fmicb.2020.00057 -
Applied and Environmental Microbiology Aug 2022Bacterial extracellular vesicles (BEVs) released from both Gram-negative and Gram-positive bacteria provide an effective means of communication and trafficking of cell...
Bacterial extracellular vesicles (BEVs) released from both Gram-negative and Gram-positive bacteria provide an effective means of communication and trafficking of cell signaling molecules. In the gastrointestinal tract (GIT) BEVs produced by members of the intestinal microbiota can impact host health by mediating microbe-host cell interactions. A major unresolved question, however, is what factors influence the composition of BEV proteins and whether the host influences protein packaging into BEVs and secretion into the GIT. To address this, we have analyzed the proteome of BEVs produced by the major human gut symbiont Bacteroides thetaiotaomicron both and in the murine GIT in order to identify proteins specifically enriched in BEVs produced . We identified 113 proteins enriched in BEVs produced the majority (62/113) of which accumulated in BEVs in the absence of any changes in their expression by the parental cells. Among these selectively enriched proteins, we identified dipeptidyl peptidases and an asparaginase and confirmed their increased activity in BEVs produced . We also showed that intact BEVs are capable of degrading bile acids via a bile salt hydrolase. Collectively these findings provide additional evidence for the dynamic interplay of host-microbe interactions in the GIT and the existence of an active mechanism to drive and enrich a selected group of proteins for secretion into BEVs in the GIT. The gastrointestinal tract (GIT) harbors a complex community of microbes termed the microbiota that plays a role in maintaining the host's health and wellbeing. How this comes about and the nature of microbe-host cell interactions in the GIT is still unclear. Recently, nanosized vesicles naturally produced by bacterial constituents of the microbiota have been shown to influence responses of different host cells although the molecular basis and identity of vesicle-born bacterial proteins that mediate these interactions is unclear. We show here that bacterial extracellular vesicles (BEVs) produced by the human symbiont Bacteroides thetaiotaomicron in the GIT are enriched in a set of proteins and enzymes, including dipeptidyl peptidases, an asparaginase and a bile salt hydrolase that can influence host cell biosynthetic pathways. Our results provide new insights into the molecular basis of microbiota-host interactions that are central to maintaining GIT homeostasis and health.
Topics: Animals; Asparaginase; Bacteria; Bacteroides thetaiotaomicron; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; Extracellular Vesicles; Gastrointestinal Microbiome; Humans; Mice; Proteome
PubMed: 35916501
DOI: 10.1128/aem.00533-22 -
IScience Sep 2023Biglycan (BGN) is a proteoglycan with branch chains and highly expressed in enteric neurons in the tumor tissue of colorectal cancer (CRC), which is negatively...
Biglycan (BGN) is a proteoglycan with branch chains and highly expressed in enteric neurons in the tumor tissue of colorectal cancer (CRC), which is negatively associated with survival rates in patients with CRC. However, how the proteoglycan promotes the progress of CRC through interacting with bacteria and regulating the immune response of enteric neurons remains largely unknown. In the present study, we found that biglycan deficiency changed tumor distribution in a colitis-associated colon cancer model. Furthermore, we revealed that BGN deficiency inhibits tumor growth in an allograft tumor model and the migration of cancer cell by upregulating interleukin-10 expression in enteric neurons. Significantly, we demonstrated that biglycan deficiency enriched the abundance of through competing with it for chondroitin sulfate to inhibit CRC progress. Our work provided new insights into the interaction between host proteoglycan and gut microbiota as well as the role of enteric neurons in the tumor microenvironment.
PubMed: 37664615
DOI: 10.1016/j.isci.2023.107515