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Humans consume alginate in the form of seaweed, food hydrocolloids, and encapsulations, making the digestion of this mannuronic acid (M) and guluronic acid (G) polymer of key interest for human health. To increase knowledge on alginate degradation in the gut, a gene catalog from human feces was mined for potential alginate lyases (ALs). The predicted ALs were present in nine species of the Bacteroidetes phylum, of which two required supplementation of an endo-acting AL, expected to mimic cross-feeding in the gut. However, only a new isolate grew on alginate. Wholegenome sequencing of this alginate-utilizing isolate suggested that it is a new Bacteroides ovatus strain harboring a polysaccharide utilization locus (PUL) containing three ALs of families: PL6, PL17, and PL38. The BoPL6 degraded polyG to oligosaccharides of DP 1-3, and BoPL17 released 4,5-unsaturated monouronate from polyM. BoPL38 degraded both alginates, polyM, polyG, and polyMG, in endo-mode; hence, it was assumed to deliver oligosaccharide substrates for BoPL6 and BoPL17, corresponding well with synergistic action on alginate. BoPL17 and BoPL38 crystal structures, determined at 1.61 and 2.11 Å, respectively, showed (a/a)6-barrel + anti-parallel ß-sheet and (a/a)7-barrel folds, distinctive for these PL families. BoPL17 had a more open active site than the two homologous structures. BoPL38 was very similar to the structure of an uncharacterized PL38, albeit with a different triad of residues possibly interacting with substrate in the presumed active site tunnel. Altogether, the study provides unique functional and structural insights into alginate-degrading lyases of a PUL in a human gut bacterium. [ABSTRACT FROM AUTHOR]

Attention-deficit/hyperactivity disorder (ADHD) is a highly heterogeneous psychiatric disorder that can have three phenotypical presentations: inattentive (I-ADHD), hyperactive-impulsive (HI-ADHD), and combined (C-ADHD). Environmental factors correlated with the gut microbiota community have been implicated in the development of ADHD. However, whether different ADHD symptomatic presentations are associated with distinct microbiota compositions and whether patients could benefit from the correction of aberrant bacterial colonization are still largely unclear. We carried out metagenomic shotgun analysis with 207 human fecal samples to characterize the gut microbial profiles of patients with ADHD grouped according to their phenotypical presentation. Then, we transplanted the candidate low-abundance bacteria identified in patient subgroups into ADHD rats and evaluated ADHD-associated behaviors and neuronal activation in these rats. Patients with C-ADHD had a different gut microbial composition from that of healthy controls (HCs) (p = .02), but not from that of I-ADHD patients. Eight species became progressively attenuated or enriched when comparing the compositions of HCs to those of I-ADHD and C-ADHD; in particular, the abundance of Bacteroides ovatus was depleted in patients with C-ADHD. In turn, Bacteroides ovatus supplementation ameliorated spatial working memory deficits and reversed θ electroencephalogram rhythm alterations in ADHD rats. In addition, Bacteroides ovatus induced enhanced neuronal activation in the hippocampal CA1 subregion. These findings indicate that gut microbial characteristics that are unique to patients with C-ADHD may be masked when considering a more heterogeneous group of patients. We link the gut microbiota to brain function in an ADHD animal model, suggesting the relevance of testing a potential bacteria-based intervention for some aspects of ADHD.

Acute lower gastrointestinal GVHD (aLGI-GVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation. Although the intestinal microbiota is associated with the incidence of aLGI-GVHD, how the intestinal microbiota impacts treatment responses in aLGI-GVHD has not been thoroughly studied. In a cohort of patients with aLGI-GVHD (n = 37), we found that non-response to standard therapy with corticosteroids was associated with prior treatment with carbapenem antibiotics and a disrupted fecal microbiome characterized by reduced abundances of Bacteroides ovatus. In a murine GVHD model aggravated by carbapenem antibiotics, introducing B. ovatus reduced GVHD severity and improved survival. These beneficial effects of Bacteroides ovatus were linked to its ability to metabolize dietary polysaccharides into monosaccharides, which suppressed the mucus-degrading capabilities of colonic mucus degraders such as Bacteroides thetaiotaomicron and Akkermansia muciniphila , thus reducing GVHD-related mortality. Collectively, these findings reveal the importance of microbiota in aLGI-GVHD and therapeutic potential of B. ovatus. [Display omitted] • Clinical steroid-refractory GVHD is associated with reduced Bacteroides ovatus • Introduction of B. ovatus after meropenem reduces experimental GVHD-related mortality • The beneficial effects of B. ovatus are linked to its ability to produce xylose • B. ovatus suppresses the mucus-degrading capabilities of colonic mucus degraders Hayase et al. discover that Bacteroides ovatus reduces the severity of graft-versus-host disease (GVHD), a complication of hematopoietic cell transplantation, by suppressing mucus-degrading gut microbes. These beneficial effects of B. ovatus are linked to the metabolism of dietary polysaccharides into monosaccharides and highlight the therapeutic potential of B. ovatus. [ABSTRACT FROM AUTHOR]

Rhamnogalacturonan lyase (RGL) cleaves backbone α-1,4 glycosidic bonds between L-rhamnose and D-galacturonic acid residues in type I rhamnogalacturonan (RG-I) by β-elimination to generate RG oligosaccharides with various degrees of polymerization. Here, we cloned, expressed, purified and biochemically characterized two RGLs (Bo3128 and Bo4416) in the PL11 family from Bacteroides ovatus ATCC 8483. Bo3128 and Bo4416 displayed maximal activity at pH 9.5 and pH 6.5, respectively. Whereas the activity of Bo3128 could be increased 1.5 fold in the presence of 5 mM Ca2+, Bo4416 required divalent metal ions to show any enzymatic activity. Both of RGLs showed a substrate preference for RG-I compared to other pectin domains. Bo4416 and Bo3128 primarily yielded unsaturated RG oligosaccharides, with Bo3128 also producing them with short side chains, with yields of 32.4 and 62.4%, respectively. Characterization of both RGLs contribute to the preparation of rhamnogalacturonan oligosaccharides, as well as for the analysis of the fine structure of RG-I pectins.

Rhamnogalacturonan lyase (RGL) cleaves backbone α-1,4 glycosidic bonds between L-rhamnose and D-galacturonic acid residues in type I rhamnogalacturonan (RG-I) by β-elimination to generate RG oligosaccharides with various degrees of polymerization. Here, we cloned, expressed, purified and biochemically characterized two RGLs (Bo3128 and Bo4416) in the PL11 family from Bacteroides ovatus ATCC 8483. Bo3128 and Bo4416 displayed maximal activity at pH 9.5 and pH 6.5, respectively. Whereas the activity of Bo3128 could be increased 1.5 fold in the presence of 5 mM Ca2+, Bo4416 required divalent metal ions to show any enzymatic activity. Both of RGLs showed a substrate preference for RG-I compared to other pectin domains. Bo4416 and Bo3128 primarily yielded unsaturated RG oligosaccharides, with Bo3128 also producing them with short side chains, with yields of 32.4 and 62.4%, respectively. Characterization of both RGLs contribute to the preparation of rhamnogalacturonan oligosaccharides, as well as for the analysis of the fine structure of RG-I pectins. [ABSTRACT FROM AUTHOR]

ABSTRACT A multigene polysaccharide utilization locus (PUL) encoding enzymes and surface carbohydrate (glycan)-binding proteins (SGBPs) was recently identified in prominent members of Bacteroidetes in the human gut and characterized in Bacteroides ovatus. This PUL-encoded system specifically targets mixed-linkage β1,3-1,4-glucans, a group of diet-derived carbohydrates that promote a healthy microbiota and have potential as prebiotics. The BoSGBPMLG-A protein encoded by the BACOVA_2743 gene is a SusD-like protein that plays a key role in the PUL’s specificity and functionality. Here, we perform a detailed analysis of the molecular determinants underlying carbohydrate binding by BoSGBPMLG-A, combining carbohydrate microarray technology with quantitative affinity studies and a high-resolution X-ray crystallography structure of the complex of BoSGBPMLG-A with a β1,3-1,4-nonasaccharide. We demonstrate its unique binding specificity toward β1,3-1,4-gluco-oligosaccharides, with increasing binding affinities up to the octasaccharide and dependency on the number and position of β1,3 linkages. The interaction is defined by a 41-Å-long extended binding site that accommodates the oligosaccharide in a mode distinct from that of previously described bacterial β1,3-1,4-glucan-binding proteins. In addition to the shape complementarity mediated by CH-π interactions, a complex hydrogen bonding network complemented by a high number of key ordered water molecules establishes additional specific interactions with the oligosaccharide. These support the twisted conformation of the β-glucan backbone imposed by the β1,3 linkages and explain the dependency on the oligosaccharide chain length. We propose that the specificity of the PUL conferred by BoSGBPMLG-A to import long β1,3-1,4-glucan oligosaccharides to the bacterial periplasm allows Bacteroidetes to outcompete bacteria that lack this PUL for utilization of β1,3-1,4-glucans. IMPORTANCE With the knowledge of bacterial gene systems encoding proteins that target dietary carbohydrates as a source of nutrients and their importance for human health, major efforts are being made to understand carbohydrate recognition by various commensal bacteria. Here, we describe an integrative strategy that combines carbohydrate microarray technology with structural studies to further elucidate the molecular determinants of carbohydrate recognition by BoSGBPMLG-A, a key protein expressed at the surface of Bacteroides ovatus for utilization of mixed-linkage β1,3-1,4-glucans. We have mapped at high resolution interactions that occur at the binding site of BoSGBPMLG-A and provide evidence for the role of key water-mediated interactions for fine specificity and affinity. Understanding at the molecular level how commensal bacteria, such as prominent members of Bacteroidetes, can differentially utilize dietary carbohydrates with potential prebiotic activities will shed light on possible ways to modulate the microbiome to promote human health.

The incidence of anaerobic bacteremia has been increasing over the past several decades. Further, antibiotic resistance in Bacteroides is a pertinent issue. A 76-year-old man was brought to our hospital with complaints of fever, chills, and abdominal pain. Empiric antibiotics induced minimal relief. The blood culture was positive for multi-drug resistant Bacteroides ovatus. Our patient developed a periaortic abscess in the abdominal aorta and a thoracic aortic aneurysm with ulcerlike projection (ULP), which rapidly increased in size. He was transferred to the tertiary medical institution for surgical drainage. This case suggests that bacteremia can exacerbate aneurysms with ulcerative lesions. Anaerobic bacteremia is a possible differential diagnosis when periaortic abscess formation is present. Early surgical consultation and appropriate antibiotic selection are crucial in anaerobic bacteremia treatment. [ABSTRACT FROM AUTHOR]

A novel β-1,4-xylosidase was identified from the genome of Bacteroides ovatus strain ATCC 8483 and overexpressed in Escherichia coli BL21 (DE3) cells. The molecular weight of recombinant enzyme named BoXyl43A was calculated to be 37.1 kDa. Using p-nitrophenyl-β-D-xylopyranoside (pNPβXyl) as substrate, BoXyl43A was most active at pH 7.0 and 35 °C. The enzyme could be activated by Mg2+ and Mn2+. The Km and Vmax of BoXyl43A against pNPβXyl were 1.71 ± 0.21 mM, 7.41 ± 0.81 μmol/min/mg, respectively. BoXyl43A hydrolyzed xylooligosaccharide to produce D-xylose as main product, indicating that BoXyl43A acted as an exo-β-1,4-xylosidase. The mixture of BoXyl43A and PoAbf62A (α-L-arabinofuranosidase) exhibited significant synergistic effects on the degradation of arabinoxylan. Therefore, BoXyl43A would be a useful tool to degrade hemicellulose. [ABSTRACT FROM AUTHOR]

Inflammatory bowel disease (IBD) is driven by dysfunction between host genetics, the microbiota, and immune system. Knowledge gaps remain regarding how IBD genetic risk loci drive gut microbiota changes. The Crohn’s disease risk allele ATG16L1 T300A results in abnormal Paneth cells due to decreased selective autophagy, increased cytokine release, and decreased intracellular bacterial clearance. To unravel the effects of ATG16L1 T300A on the microbiota and immune system, we employed a gnotobiotic model using human fecal transfers into ATG16L1 T300A knock-in mice. We observed increases in Bacteroides ovatus and Th1 and Th17 cells in ATG16L1 T300A mice. Association of altered Schaedler flora mice with B. ovatus specifically increased Th17 cells selectively in ATG16L1 T300A knock-in mice. Changes occur before disease onset, suggesting that ATG16L1 T300A contributes to dysbiosis and immune infiltration prior to disease symptoms. Our work provides insight for future studies on IBD subtypes, IBD patient treatment and diagnostics.

Bacteroides ovatus ELH-B2 is considered as a potential next-generation probiotic due to its preventive effects on lipopolysaccharides-associated inflammation and intestinal microbiota disorders in mice. To study safety issues associated with B. ovatus ELH-B2, we conducted comprehensive and systematic experiments, including in vitro genetic assessments of potential virulence and antimicrobial resistance genes, and an in vivo acute toxicity study of both immunocompetent and immunosuppressed mice via cyclophosphamide treatment. The results indicated that this novel strain is non-toxigenic, fragilysin is not expressed, and most of potential virulence genes are correlated with cellular structures such as capsular polysaccharide and polysaccharide utilizations. The antibiotic resistance features are unlikely be transferred to other intestinal microorganisms as no plasmids nor related genomic islands were identified. Side effects were not observed in mice. B. ovatus ELH-B2 also alleviated the damages caused by cyclophosphamide injection.

Bacteroides ovatus ELH-B2 is considered as a potential next-generation probiotic due to its preventive effects on lipopolysaccharides-associated inflammation and intestinal microbiota disorders in mice. To study safety issues associated with B. ovatus ELH-B2, we conducted comprehensive and systematic experiments, including in vitro genetic assessments of potential virulence and antimicrobial resistance genes, and an in vivo acute toxicity study of both immunocompetent and immunosuppressed mice via cyclophosphamide treatment. The results indicated that this novel strain is non-toxigenic, fragilysin is not expressed, and most of potential virulence genes are correlated with cellular structures such as capsular polysaccharide and polysaccharide utilizations. The antibiotic resistance features are unlikely be transferred to other intestinal microorganisms as no plasmids nor related genomic islands were identified. Side effects were not observed in mice. B. ovatus ELH-B2 also alleviated the damages caused by cyclophosphamide injection. [ABSTRACT FROM AUTHOR]

Clostridium difficile infection (CDI) is one of the most common nosocomial infections. Dysbiosis of the gut microbiota due to consumption of antibiotics is a major contributor to CDI. Recently, fecal microbiota transplantation (FMT) has been applied to treat CDI. However, FMT has important limitations including uncontrolled exposure to pathogens and standardization issues. Therefore, it is necessary to evaluate alternative treatment methods, such as bacteriotherapy, as well as the mechanism through which beneficial bacteria inhibit the growth of C. difficile. Here, we report bile acid-mediated inhibition of C. difficile by Bacteroides strains which can produce bile salt hydrolase (BSH). Bacteroides strains are not commonly used to treat CDI; however, as they comprise a large proportion of the intestinal microbiota, they can contribute to bile acid-mediated inhibition of C. difficile. The inhibitory effect on C. difficile growth increased with increasing bile acid concentration in the presence of Bacteroides ovatus SNUG 40239. Furthermore, this inhibitory effect on C. difficile growth was significantly attenuated when bile acid availability was reduced by cholestyramine, a bile acid sequestrant. The findings of this study are important due to the discovery of a new bacterial strain that in the presence of available bile acids inhibits growth of C. difficile. These results will facilitate development of novel bacteriotherapy strategies to control CDI. [ABSTRACT FROM AUTHOR]

Carrageenan, agarose, and alginate are algae-derived undigested polysaccharides that have been used as food additives for hundreds of years. Fermentation of dietary carbohydrates of our food in the lower gut of humans is a critical process for the function and integrity of both the bacterial community and host cells. However, little is known about the fermentation of these three kinds of seaweed carbohydrates by human gut microbiota. Here, the degradation characteristics of carrageenan, agarose, alginate, and their oligosaccharides, by Bacteroides xylanisolvens, Bacteroides ovatus, and Bacteroides uniforms, isolated from human gut microbiota, are studied. [ABSTRACT FROM AUTHOR]

The Bacova_02091 gene in the β-mannan utilization locus of Bacteroides ovatus encodes a family GH36 α-galactosidase (BoGal36A), transcriptionally upregulated during growth on galactomannan. Characterization of recombinant BoGal36A reveals unique properties compared to other GH36 α-galactosidases, which preferentially hydrolyse terminal α-galactose in raffinose family oligosaccharides. BoGal36A prefers hydrolysing internal galactose substitutions from intact and depolymerized galactomannan. BoGal36A efficiently releases (> 90%) galactose from guar and locust bean galactomannans, resulting in precipitation of the polysaccharides. As compared to other GH36 structures, the BoGal36A 3D model displays a loop deletion, resulting in a wider active site cleft which likely can accommodate a galactose-substituted polymannose backbone. [ABSTRACT FROM AUTHOR]

Alginate (Alg) has a long history as a food ingredient in East Asia. However, the human gut microbes responsible for the degradation of alginate and its derivatives have not been fully understood yet. Here, we report that alginate and the low molecular polymer derivatives of mannuronic acid oligosaccharides (MO) and guluronic acid oligosaccharides (GO) can be completely degraded and utilized at various rates by fecal microbiota obtained from six Chinese individuals. However, the derivative of propylene glycol alginate sodium sulfate (PSS) was not hydrolyzed. The bacteria having a pronounced ability to degrade Alg, MO and GO were isolated from human fecal samples and were identified as Bacteroides ovatus , Bacteroides xylanisolvens , and Bacteroides thetaiotaomicron . Alg, MO and GO can increase the production level of short chain fatty acids (SCFA), but GO generates the highest level of SCFA. Our data suggest that alginate and its derivatives could be degraded by specific bacteria in the human gut, providing the basis for the impacts of alginate and its derivates as special food additives on human health. [ABSTRACT FROM AUTHOR]

Acute gastrointestinal intestinal GVHD (aGI-GVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation, and the intestinal microbiota is known to impact on its severity. However, an association between treatment response of aGI-GVHD and the intestinal microbiota has not been well-studied. In a cohort of patients with aGI-GVHD (n=37), we found that non-response to standard therapy with corticosteroids was associated with prior treatment with carbapenem antibiotics and loss of Bacteroides ovatus from the microbiome. In a mouse model of carbapenem-aggravated GVHD, introducing Bacteroides ovatus reduced severity of GVHD and improved survival. Bacteroides ovatus reduced degradation of colonic mucus by another intestinal commensal, Bacteroides thetaiotaomicron , via its ability to metabolize dietary polysaccharides into monosaccharides, which then inhibit mucus degradation by Bacteroides thetaiotaomicron and reduce GVHD-related mortality., Competing Interests: Declaration of interests R.R.J. has served as a consultant or advisory board member for Merck, Microbiome DX, Karius, MaaT Pharma, LISCure, Seres, Kaleido, and Prolacta and has received patent license fee or stock options from Seres and Kaleido. E.J.S. has served as a consultant or advisory board member for Adaptimmune, Axio, Navan, Fibroblasts and FibroBiologics, NY Blood Center, and Celaid Therapeutics and has received patent license fee from Takeda and Affimed. E.H., M.A.J., J.L.K., and R.R.J. are inventors on a patent application by The University of Texas MD Anderson Cancer Center supported by results of the current study entitled, “Methods and Compositions for Treating Cancer therapy-induced Neutropenic Fever and/or GVHD.”

Aging is associated with low bone and lean mass as well as alterations in the gut microbiota (GM). In this study, we determined whether the reduced bone mass and relative lean mass observed in old mice could be transferred to healthy young mice by GM transplantation (GMT). GM from old (21-month-old) and young adult (5-month-old) donors was used to colonize germ-free (GF) mice in three separate studies involving still growing 5- or 11-week-old recipients and 17-week-old recipients with minimal bone growth. The GM of the recipient mice was similar to that of the donors, demonstrating successful GMT. GM from old mice did not have statistically significant effects on bone mass or bone strength, but significantly reduced the lean mass percentage of still growing recipient mice when compared with recipients of GM from young adult mice. The levels of propionate in the cecum of mice receiving old donor GM were significantly lower than those in mice receiving young adult donor GM. Bacteroides ovatus was enriched in the microbiota of recipient mice harboring GM from young adult donors. The presence of B. ovatus was not only significantly associated with high lean mass percentage in mice, but also with lean mass adjusted for fat mass in the large human HUNT cohort. In conclusion, GM from old mice reduces lean mass percentage but not bone mass in young, healthy, still growing recipient mice. Future studies are warranted to determine whether GM from young mice improves the musculoskeletal phenotype of frail elderly recipient mice.

Background: Bacteroides ovatus, a member of the genus Bacteroides, is considered for use in molecular-based methods as a general fecal indicator. However, knowledge on its fate and persistence after a fecal contamination event remains limited. In this study, the persistence of B. ovatus was evaluated under simulated sunlight exposure and in conditions similar to freshwater and seawater. By combining propidium monoazide (PMA) treatment and quantitative polymerase chain reaction (qPCR) detection, the decay rates of B. ovatus were determined in the presence and absence of exogenous photosensitizers and in salinity up to 39.5 parts per thousand at 27°C. Results: UVB was found to be important for B. ovatus decay, averaging a 4 log10 of decay over 6 h of exposure without the presence of extracellular photosensitizers. The addition of NaNO2, an exogenous sensitizer producing hydroxyl radicals, did not significantly change the decay rate of B. ovatus in both low and high salinity water, while the exogenous sensitizer algae organic matter (AOM) slowed down the decay of B. ovatus in low salinity water. At seawater salinity, the decay rate of B. ovatus was slower than that in low salinity water, except when both NaNO2 and AOM were present. Conclusion: The results of laboratory experiments suggest that if B. ovatus is released into either freshwater or seawater environment in the evening, 50% of it may be intact by the next morning; if it is released at noon, only 50% may be intact after a mere 5 min of full spectrum irradiation on a clear day. This study provides a mechanistic understanding to some of the important environmental relevant factors that influenced the inactivation kinetics of B. ovatus in the presence of sunlight irradiation, and would facilitate the use of B. ovatus to indicate the occurrence of fecal contamination. [ABSTRACT FROM AUTHOR]

The tumor-specific Thomsen-Friedenreich antigen (TFα, CD176) is an attractive target for a cancer vaccine, especially as TF-directed antibodies play an important role in cancer immunosurveillance. However, synthetic TF vaccines have not overcome the low intrinsic immunogenicity of TF. Since natural TF-directed antibodies present in human sera are generated in response to microbes found in the gastrointestinal tract, microbial TF structures are obviously more immunogenic than synthetic TF. We recently isolated a new strain (D-6) of the human gut bacterium Bacteroides ovatus, which carries the true TFα antigen. Here, we present experimental data on the immunogenicity of this strain. Mice immunized with B. ovatus D-6 in the absence of adjuvants developed specific anti-TFα IgM and IgG antibodies which also bound to human cancer cells carrying TFα. Our data suggest that B. ovatus D-6 presents a unique TFα-specific immunogenicity based on a combination of several inherent properties including: expression of the true TFα antigen, clustering and accessible presentation of TFα as repetitive side chains on a capsular polysaccharide, and intrinsic adjuvant properties. Therefore, B. ovatus strain D-6 is an almost perfect candidate for the development of the first adjuvant-free TFα-specific anti-tumor vaccine. [ABSTRACT FROM AUTHOR]

The Thomsen–Friedenreich antigen (TF; CD176, Galβ1-3GalNAcα-) is a tumor-specific carbohydrate antigen and a promising therapeutic target. Antibodies that react with this antigen are frequently found in the sera of healthy adults and are assumed to play a role in cancer immunosurveillance. In this study, we examined the occurrence of α-anomeric TF (TFα) on a large variety of gastrointestinal bacteria using a novel panel of well-characterized monoclonal antibodies. Reactivity with at least one anti-TF antibody was found in 13% (16 of 122) of strains analyzed. A more in-depth analysis, using monoclonal antibodies specific for α- and β-anomeric TF in combination with periodate oxidation, revealed that only two novel Bacteroides ovatus strains (D-6 and F–1), isolated from the faeces of healthy persons by TF-immunoaffinity enrichment, possessed structures that are immunochemically identical to the true TFα antigen. The TF-positive capsular polysaccharide structure of strain D-6 was characterized by mass spectrometry, monosaccharide composition analysis, glycosidase treatments and immunoblot staining with TFα- and TFβ-specific antibodies. The active antigen was identified as Galβ1-3GalNAc-, which was α-anomerically linked as a branching structure within a heptasaccharide repeating unit. We conclude that structures immunochemically identical to TFα are extremely rare on the surface of human intestinal bacteria and may only be identifiable by binding of both antibodies, NM-TF1 and NM-TF2, which recognize a complete immunomolecular imprint of the TFα structure. The two novel B. ovatus strains isolated in this study may provide a basis for the development of TF-based anti-tumor vaccines. [ABSTRACT FROM AUTHOR]

This study was aimed to evaluate the role of commensal Gramnegative bacterium Bacteroides ovatus in murine model of chronic intestinal inflammation. The attempt to induce chronic colitis was done in Bacteroides ovatus-monoassociated, germfree and conventional mice either in immunocompetent (BALB/c) mice or in mice with severe combined immunodeficiency (SCID), using 2.5 % dextran-sodium sulfate (DSS) in drinking water (7 days DSS, 7 days water, 7 days DSS). Conventional mice developed chronic colitis. Some of germ-free BALB/c and the majority of germ-free SCID mice did not survive the long-term treatment with DSS due to massive bleeding into the intestinal lumen. However, monocolonization of germ-free mice of both strains with Bacteroides ovatus prior to long-term treatment with DSS protected mice from bleeding, development of intestinal inflammation and precocious death. We observed that though DSS-treated Bacteroides ovatus-colonized SCID mice showed minor morphological changes in colon tissue, jejunal brushborder enzyme activities such as ?-glutamyltranspeptidase, lactase and alkaline phosphatase were significantly reduced in comparison with DSS-untreated Bacteroides ovatus-colonized mice. This modulation of the enterocyte ?-glutamyltranspeptidase localized to the brush border membrane has been described for the first time. This enzyme is known to reflect an imbalance between pro-oxidant and anti-oxidant mechanisms, which could be involved in protective effects of colonization of germ-free mice with Bacteroides ovatus against DSS injury. [ABSTRACT FROM AUTHOR]

m.d. farrar, t.r. whitehead, j. lan, p. dilger, r. thorpe, k.t. holland and s.r. carding. 2005.The aim of this work was to engineer a gut commensal bacterium,Bacteroidesovatus, to produce and secrete a biologically active cytokine in a regulated manner as a basis for novel immunotherapies for chronic gut disorders.Bacteroides ovatuswas engineered to produce murine interleukin-2 (MuIL2) intracellularly in response to xylan in culture media by inserting the MuIL2 gene into the xylanase operon of the organism. A second strain was engineered to secrete MuIL2 by addingBacteroides fragilisenterotoxin secretion signal sequence to the protein. The recombinant strains produced MuIL2 only in the presence of xylan as determined by ELISA of cell lysates and culture supernatants. The IL2-dependent cell line CTLL-2 was used to demonstrate that MuIL2 produced by bothB. ovatusstrains was biologically active. This activity could be blocked by an anti-IL2 neutralizing antibody. The xylan-inducible nature of this system was demonstrated by RT-PCR.Bacteroides ovatuswas successfully engineered to produce and secrete biologically active MuIL2 in a xylan-inducible manner.The production and secretion of a biologically active mammalian protein by a member of the gut microflora could lead to the development of new long-term immunotherapies for inflammatory gut diseases. [ABSTRACT FROM AUTHOR]

Hyaluronan (HA) has been widely used as a dietary supplement which can be degraded by gut microbiota. However, the interactions between HA and gut microbiota have not been fully characterized. Here, using an in vitro system, we found that HA is readily fermented by human gut microbiota but with differing fermentative activities among individuals. HA-fermentation boosted Bacteroides spp., Bifidobacterium spp., Dialister spp., Faecalibacterium spp. and produced a significant amount of acetate, propionate and butyrate. Fermentation products profiling indicated that HA could be degraded into unsaturated even-numbered and saturated odd-numbered oligosaccharides. Further, polysaccharide lyases (PLs) and glycoside hydrolases (GHs) including GH88, PL8, PL29, PL35 and PL33 were identified from B. ovatus E3, which can help to explain the structure of the fermentation products. Collectively, our study sheds new light into the metabolism of HA and forms the basis for understanding the bioavailability of HA from a gut microbiota perspective. [Display omitted] • HA is fermented by gut microbiota with differing fermentative activities. • HA fermentation can modulate the gut microbiota and produced SCFAs. • HA was degraded into unsaturated even-numbered and saturated odd-numbered oligosaccharides. • Bacteroides spp. play critical roles in the HA degradation. • GH88, PL8, PL29, PL35 and PL33 were identified as HA-active enzymes. [ABSTRACT FROM AUTHOR]

Heparin and its derivative are commonly used as injectable anticoagulants in clinical procedures, but possess poor oral bioavailability. To explore the role of gut microbiota in the poor oral effect of heparin, the degradation profiles of heparin on six human gut microbiota were investigated. The heparin-degradation ability varied significantly among individuals. Furthermore, two strains of heparin-degrading bacteria, Bacteroides ovatus A2 and Bacteroides cellulosilyticus B19, were isolated from the gut microbiota of different individuals and the degradation products of the isolates were profiled. The ΔUA2S-GlcNS6S was the major end product with almost no desulfation. 3- O -sulfo group-containing tetrasaccharides were detected, which indicated that the antithrombin binding site was broken and this explained the lost anticoagulant activity of heparin. Collectively, the present study assessed the degradation profiles of heparin by human gut microbiota and provided references for the development of oral administration of heparin from a gut microbiota perspective. • The heparin-degradation ability varied significantly among individuals. • B. ovatus and B. cellulosilyticus isolated from human fecal could degrade heparin. • The ΔUA2S-GlcNS6S was the major end degradation product in all isolates. • The products of 3- O -sulfo group-containing tetrasacchardes were detected. • Several breakdown products explained the destroyed anticoagulant activity of heparin. [ABSTRACT FROM AUTHOR]

B. ovatus is a member of the human gut microbiota with a broad capability to degrade complex glycans. Here we show that B. ovatus degrades plant polysaccharides in a preferential order, and that glycan structural complexity plays a role in determining the prioritisation of polysaccharide usage. • Bacteroides ovatus has a broad capability to degrade complex glycans. • B. ovatus degrades plant glycans in a preferential order. • Glycan structural complexity plays a role in determining prioritisation of glycan usage. [ABSTRACT FROM AUTHOR]

Yeast mannan (YM) is an indigestible water-soluble polysaccharide of the yeast cell wall. In vitro fecal fermentation studies showed that YM could exhibit a notable prebiotic effect. The aim of this randomized, double-blind, placebo-controlled study was to assess the efficacy of YM intake on the intestinal environment and skin condition. One hundred and ten healthy female subjects aged 30–49 years were supplemented with YM or placebo for eight weeks. Skin dryness was set as the primary endpoint. No side effects were observed during the study. Microbiota analyses revealed that YM intake selectively increased the relative abundance of Bacteroides thetaiotaomicron and Bacteroides ovatus compared to that by placebo. Feces and urine analyses showed that YM intake lowered the concentration of fecal p-cresol, indole, and skatole, and elevated urinal equol levels compared to those in placebo. Furthermore, YM supplementation ameliorated subjective skin dryness. This study suggests that YM intake could promote beneficial Bacteroides and improve the intestinal environment and skin condition. [ABSTRACT FROM AUTHOR]

Fecal IgA production depends on colonization by a gut microbiota. However, the bacterial strains that drive gut IgA production remain largely unknown. Here, we assessed the IgA-inducing capacity of a diverse set of human gut microbial strains by monocolonizing mice with each strain. We identified Bacteroides ovatus as the species that best induced gut IgA production. However, this induction varied bimodally across different B. ovatus strains. The high IgA-inducing B. ovatus strains preferentially elicited more IgA production in the large intestine through the T cell-dependent B cell-activation pathway. Remarkably, a low-IgA phenotype in mice could be robustly and consistently converted into a high-IgA phenotype by transplanting a multiplex cocktail of high IgA-inducing B. ovatus strains but not individual ones. Our results highlight the critical importance of microbial strains in driving phenotype variation in the mucosal immune system and provide a strategy to robustly modify a gut immune phenotype, including IgA production. • Bacteroides ovatus strain variation drives either high or low fecal IgA • CD4+ T cells are critical in B. ovatus -mediated gut IgA production • Cocktails of IgAhigh B. ovatus strains convert mice from low- to high-IgA producers Yang et al. identify that different Bacteroides ovatus strains induce either high or low baseline fecal IgA in mice. Cocktails of IgAhigh B. ovatus strains convert mice from low-IgA to high-IgA producers. This demonstrates a role of microbial strains in immune variation and a microbiota-based immune modulation strategy. [ABSTRACT FROM AUTHOR]

The response to treatment with biologic drugs, in patients with Crohn's disease, could be associated with changes in gut microbiota composition. The aim of our study was to analyse the modification of microbiota during adalimumab therapy in patients with Crohn's disease. We performed a prospective study in patients with Crohn's disease analysing gut microbiota before start of adalimumab therapy (T0) and after six months of therapy (T1). Among the 20 included patients, the phylum Proteobacteria fell from 15.7 ± 3.5% at T0 to 10.3 ± 3.4% at T1 (p = 0.038). Furthermore, the trend in relation to therapeutic success was analysed. Regarding bacterial phyla, Proteobacteria decreased in patients in whom therapeutic success was obtained, passing from a value of 15.8% (± 4.6%) to 6.8 ± 3.1% (p = 0.049), while in non-responder patients, percentages did not change (T0 = 15.6 ± 5.7%, T1 = 16.8 ± 7.6%, p = 0.890). Regarding the Lachnospiraceae family, in patients with normalization of C reactive protein six 6 months of adalimumab therapy, it increased from 16.6 ± 3.1% at T0 to 23.9 ± 2.6% at T1 (p = 0.049). In conclusion, in patients who respond to Adalimumab therapy by decreasing inflammation, there is a trend of intestinal eubiosis being restored. [ABSTRACT FROM AUTHOR]

The galactomannan utilization locus ( Bo ManPUL) of the human gut bacterium Bacteroides ovatus encodes Bo Man26B, a cell-surface-exposed endomannanase whose functional and structural features have been unclear. Our study now places Bo Man26B in context with related enzymes and reveals the structural basis for its specificity. Bo Man26B prefers longer substrates and is less restricted by galactose side-groups than the mannanase Bo Man26A of the same locus. Using galactomannan, Bo Man26B generated a mixture of (galactosyl) manno-oligosaccharides shorter than mannohexaose. Three defined manno-oligosaccharides had affinity for the SusD-like surface-exposed glycan-binding protein, predicted to be implicated in saccharide transport. Co-incubation of Bo Man26B and the periplasmic α-galactosidase Bo Gal36A increased the rate of galactose release by about 10-fold compared with the rate without Bo Man26B. The results suggested that Bo Man26B performs the initial attack on galactomannan, generating oligosaccharides that after transport to the periplasm are processed by Bo Gal36A. A crystal structure of Bo Man26B with galactosyl-mannotetraose bound in subsites -5 to -2 revealed an open and long active-site cleft with Trp-112 in subsite -5 concluded to be involved in mannosyl interaction. Moreover, Lys-149 in the -4 subsite interacted with the galactosyl side-group of the ligand. A phylogenetic tree consisting of GH26 enzymes revealed four strictly conserved GH26 residues and disclosed that Bo Man26A and Bo Man26B reside on two distinct phylogenetic branches (A and B). The three other branches contain lichenases, xylanases, or enzymes with unknown activities. Lys-149 is conserved in a narrow part of branch B, and Trp-112 is conserved in a wider group within branch B., (© 2019 Bågenholm et al.)