Bacteroides Dorei Research Articles

P785 Association of Bacteroidetes with endoscopic activity in patients with inflammatory bowel disease

Background: The role of gut microbiota on the etiopathogenesis of inflammatory bowel disease (IBD), both in Crohn's disease (CD) and ulcerative colitis (UC), is not well known. Most studies of human gut microbiota rely on the non-invasive collection of stool samples. However, the analysis of the fecal microbiota may not reflect the role of the mucosa-associated microbes. Mucosa-associated germs live in close proximity to the intestinal epithelium and are in contact with the cells of the innate immune system directly involved in the inflammatory response. The aim of this study was to investigate the genotypes of Bacteroidetes microbiota from colon biopsies of IBD patients and to determine their relationship with the endoscopic activity of the disease. Methods: A single-center, observational cross-sectional study was designed. Consecutive patients with Crohn's disease (CD) and ulcerative colitis (UC) who attended the Endoscopy Unit for colonoscopy were included. Colonic biopsies were taken to characterize microbiota. We did this by using a restriction fragment length polymorphism (RFLP) analysis on PCR products targeting the 16SrRNA genes of Bacteroidetes digested with HinfI, PciI, DpnII and AciI. Inactive UC was defined as a Mayo endoscopic score of 0. Inactive CD was defined as a SES-CD ≤2. The association of endoscopic activity with demographic (gender, age and smoking habits) and analytical (VSG, PCR and platelets) factors was also evaluated. The results were expressed as prevalence and analyzed using logistic regression. Results: 52 consecutive IBD patients (28 CD and 24 UC) were included. 33 patients showed endoscopic activity of the disease (20 CDa and 13 UCa). A total of eight genotypes of Bacteroidetes called N1, C1-C5, CB 10 and CB13 were detected. N1 is probably a strain of Bacteroides dorei, and C1 and C2 B.vulgaris strains. While the presence of N1 and C1 genotypes was consistent in patients with active and inactive IBD, the percentage of C4 genotypes in patients with UCa and CDa was very high (81.8%) compared to patients without activity (36.8%) (p=0.001). C3 genotype was observed in 4/19 inactive IBD patients and in 12/33 of active IBD patients (p=0.24). Other genotypes were found sporadically in IBD biopsies. No differences were observed between the genotype of patients with CD or UC. After multivariate analysis, C4 genotype in colon biopsies was associated with endoscopic activity of the disease (OR 8.58, 95% CI 2.16–34.08) (p=0.02). Conclusions: The presence of genotype C4 of Bacteroidetes is associated with the endoscopic activity of IBD, in both CD and UC. Future studies are needed to determinate their role as an activity biomarker.

Imbalance of bacteriome profiles within the Finnish Diabetes Prediction and Prevention study: Parallel use of 16S profiling and virome sequencing in stool samples from children with islet autoimmunity and matched controls.

We set out to explore associations between the stool bacteriome profiles and early-onset islet autoimmunity, taking into account the interactions with the virus component of the microbiome. Serial stool samples were longitudinally collected from 18 infants and toddlers with early-onset islet autoimmunity (median age 17.4 months) followed by type 1 diabetes, and 18 tightly matched controls from the Finnish Diabetes Prediction and Prevention (DIPP) cohort. Three stool samples were analyzed, taken 3, 6, and 9 months before the first detection of serum autoantibodies in the case child. The risk of islet autoimmunity was evaluated in relation to the composition of the bacteriome 16S rDNA profiles assessed by mass sequencing, and to the composition of DNA and RNA viromes. Four operational taxonomic units were significantly less abundant in children who later on developed islet autoimmunity as compared to controls-most markedly the species of Bacteroides vulgatus and Bifidobacterium bifidum. The alpha or beta diversity, or the taxonomic levels of bacterial phyla, classes or genera, showed no differences between cases and controls. A correlation analysis suggested a possible relation between CrAssphage signals and quantities of Bacteroides dorei. No apparent associations were seen between development of islet autoimmunity and sequences of yet unknown origin. The results confirm previous findings that an imbalance within the prevalent Bacteroides genus is associated with islet autoimmunity. The detected quantitative relation of the novel "orphan" bacteriophage CrAssphage with a prevalent species of the Bacteroides genus may exemplify possible modifiers of the bacteriome.

Effect of dietary interventions on the intestinal microbiota of Mongolian hosts

The gut microbiota of Mongolian hosts has distinctive characteristics due to their meat- and dairy-oriented daily diets and unique genotype. The aim of the present study was to investigate the effect of switching from the typical high protein and fat Mongolian diets to carbohydrate-rich meals composed principally of wheat, rice and naked oats on the host gut microbiota within 3 weeks. Our study took the advantage of the long sequence reads produced by the PacBio single molecule real-time sequencing technology to enable the profiling of subjects’ gut microbiota communities along the diet intervention to the species precision. We found that the bacterial richness and diversity decreased apparently along the diet intervention. During the diet intervention, the gut microbiota composition displayed no significant difference at phylum level (with major phyla of Firmicutes, Bacteroidetes, Tenericutes and Proteobacteria). The relative abundances of some genera such as Bacteroidetes, Faecalibacterium, Roseburia, Alistipes, Streptococcus, and Oscillospira were significantly altered after the diet switching started. Notably, significant changes were also observed in the proportions of the species Bacteroides dorei, Bacteroides fragilis, Bacteroides thetaiotaomicron, Ruminococcus albus, Ruminococcus faecis, Roseburia faecis and Eubacterium ventriosum. These results have demonstrated that diet and host gut microbiota is closely linked.

Current Status of Marker Genes of Bacteroides and Related Taxa for Identifying Sewage Pollution in Environmental Waters

Microbial source tracking (MST) endeavors to determine sources of fecal pollution in environmental waters by capitalizing on the association of certain microorganisms with the gastrointestinal tract and feces of specific animal groups. Several decades of research have shown that bacteria belonging to the gut-associated order Bacteroidales, and particularly the genus Bacteroides, tend to co-evolve with the host, and are, therefore, particularly suitable candidates for MST applications. This review summarizes the current research on MST methods that employ genes belonging to Bacteroidales/Bacteroides as tracers or “markers” of sewage pollution, including known advantages and deficiencies of the many polymerase chain reaction (PCR)-based methods that have been published since 2000. Host specificity is a paramount criterion for confidence that detection of a marker is a true indicator of the target host. Host sensitivity, or the prevalence of the marker in feces/waste from the target host, is necessary for confidence that absence of the marker is indicative of the absence of the pollution source. Each of these parameters can vary widely depending on the type of waste assessed and the geographic location. Differential decay characteristics of bacterial targets and their associated DNA contribute to challenges in interpreting MST results in the context of human health risks. The HF183 marker, derived from the 16S rRNA gene of Bacteroides dorei and closely related taxa, has been used for almost two decades in MST studies, and is well characterized regarding host sensitivity and specificity, and in prevalence and concentration in sewage in many countries. Other markers such as HumM2 and HumM3 show promise, but require further performance testing to demonstrate their widespread utility. An important limitation of the one-marker-one-assay approach commonly used for MST is that given the complexities of microbial persistence in environmental waters, and the methodological challenges of quantitative PCR (qPCR) in such samples, the absence of a given marker does not ensure the absence of fecal pollution in the source water. Approaches under development, such as microarray and community analysis, have the potential to improve MST practices, thereby increasing our ability to protect human and ecosystem health.

Biochar, Bentonite and Zeolite Supplemented Feeding of Layer Chickens Alters Intestinal Microbiota and Reduces Campylobacter Load.

A range of feed supplements, including antibiotics, have been commonly used in poultry production to improve health and productivity. Alternative methods are needed to suppress pathogen loads and maintain productivity. As an alternative to antibiotics use, we investigated the ability of biochar, bentonite and zeolite as separate 4% feed additives, to selectively remove pathogens without reducing microbial richness and diversity in the gut. Neither biochar, bentonite nor zeolite made any significant alterations to the overall richness and diversity of intestinal bacterial community. However, reduction of some bacterial species, including some potential pathogens was detected. The microbiota of bentonite fed animals were lacking all members of the order Campylobacterales. Specifically, the following operational taxonomic units (OTUs) were absent: an OTU 100% identical to Campylobacter jejuni; an OTU 99% identical to Helicobacter pullorum; multiple Gallibacterium anatis (>97%) related OTUs; Bacteroides dorei (99%) and Clostridium aldenense (95%) related OTUs. Biochar and zeolite treatments had similar but milder effects compared to bentonite. Zeolite amended feed was also associated with significant reduction in the phylum Proteobacteria. All three additives showed potential for the control of major poultry zoonotic pathogens.

A Necrotizing Enterocolitis-Associated Gut Microbiota Is Present in the Meconium: Results of a Prospective Study.

Anomalous intestinal microbiota development is supposedly associated with development of necrotizing enterocolitis (NEC). Our aim in this study was to identify the intestinal microbiota of patients at risk for NEC. In a prospective trial that investigated prognostic factors for development of NEC in high-risk neonates (NTR4153), 11 NEC cases were gestational age/birthweight matched with controls (ratio of 1:2). Feces were collected twice a week. We used the first feces sample of each patient (meconium), as well as the last 2 feces samples prior to development of NEC. DNA was extracted, and the bacterial 16S rRNA genes were analyzed on a MiSeq sequencer. The presence and abundance of Clostridium perfringens (8.4%) and Bacteroides dorei (0.9%) in meconium were increased in neonates who developed NEC compared with controls (0.1% and 0.2%; both species, P < .001). In post-meconium samples, the abundance of staphylococci became negatively associated with NEC development (P = .1 and P = .01 for consecutive samples); Clostridium perfringens continued to be more prevalent in NEC cases. Early enteral feeding and, in particular, breast milk were correlated with an increase in lactate-producing bacilli in post-meconium samples (ρ = -0.45; P = .004). A NEC-associated gut microbiota can be identified in meconium samples; C. perfringens continues to be associated with NEC from the first meconium till just before NEC onset. In contrast, in post-meconium, increased numbers of staphylococci were negatively associated with NEC. These findings suggest causality but this causality should be verified in trials of induced infection in animals, targeted antibiotics, and/or probiotics. CALIFORNIA trial, registered under trial number NTR4153 in the Dutch Trial Registry.

Bacterial metabolites directly modulate farnesoid X receptor activity.

BackgroundThe farnesoid X receptor (FXR), a ligand-activated transcription factor belonging to the adopted orphan receptor, plays an important role in maintaining health of the liver and intestine. In this study, we identified individual bacterial strains that directly modulated the activation of intestinal FXR.MethodsThe FXR stimulatory potential of 38 bacterial strains was determined using a stable FXR reporter system derived from intestinal epithelial cells (IEC). The induction of FXR target genes by screened FXR stimulatory bacteria was determined by real-time PCR. In addition, a high fat diet (HFD)-induced obese mouse model was used to evaluate in vivo FXR stimulatory potential of bacterial metabolites screened in this study.ResultsA luciferase assay with the FXR reporter cell line demonstrated that the FXR-stimulatory activity of most bacterial cell samples was less than 2-fold. The culture supernatants of Bacteroides dorei and Eubacterium limosum induced FXR activity and selectively regulated FXR target expression in the FXR reporter system. Treatment with B. dorei-derived metabolites strongly induced ileal bile acid binding protein (IBABP) (8.4-fold) and organic solute transporter (OST) α (3.1-fold) compared with E. limosum-derived metabolites. Furthermore, administration of B. dorei derived metabolites showed significant reduction in body weight gain, and both two bacterial metabolites reduced liver weight in obese mice compared to PBS-treated controls. Administration of each bacterial metabolites improved in serum levels of obesity-related metabolic biochemical markers such as ALT, AST, total cholesterol, and triglyceride. Furthermore, two bacterial metabolites enhanced the Fxr gene expression in the intestine and liver, and ileal Shp gene expression tended to be increased by treatment with the metabolites derived from B. dorei.ConclusionsB. dorei and E. limosum secreted the bioactive substances that directly stimulate FXR in the intestinal epithelial cells. Administration of these bacterial FXR-stimulatory metabolites improves the obesity phenotype including body weight gain, liver damage, lipid metabolism in DIO mice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-015-0045-y) contains supplementary material, which is available to authorized users.

Effects of Lactobacillus salivarius Ren on cancer prevention and intestinal microbiota in 1, 2-dimethylhydrazine-induced rat model

Probiotics have been suggested as a prophylactic measure in colon cancer. The aim of this study was to investigate the impact of Lactobacillus salivarius Ren (Ren) in modulating colonic microbiota structure and colon cancer incidence in a rat model after injection with 1,2-dimethyl hydrazine (DMH). The results indicated that oral administration of Ren could effectively suppress DMH-induced colonic carcinogenesis. A significant decrease in cancer incidence (87.5% to 25%) was detected in rats fed with a dose of 5 × 10(10) CFU/kg bodyweight per day. Using denaturing gradient gel electrophoresis and Real-time PCR combined with multivariate statistical methods, we demonstrated that injection with DMH significantly altered the rat gut microbiota, while Ren counteracted these DMH-induced adverse effects and promoted reversion of the gut microbiota close to the healthy state. Tvalue biplots followed by band sequencing identified 21 bacterial strains as critical variables affected by DMH and Ren. Injection of DMH significantly increased the amount of Ruminococcus species (sp.) and Clostridiales bacteria, as well as decreasing the Prevotella sp. Administration of Ren reduced the amount of Ruminococcus sp., Clostridiales bacteria, and Bacteroides dorei, and increased the amount of Prevotella. Real-time PCR results were consistent with the results derived by t-value biplots. These findings suggested that Ren is a potential agent for colon cancer prevention. In conclusion, the results in the present study suggest a potential therapeutic approach based on the modulation of intestinal microflora by probiotics may be beneficial in the prevention of colorectal carcinogenesis.

A model for the role of gut bacteria in the development of autoimmunity for type 1 diabetes.

Several lines of evidence suggest a role for the gut microbiome in type 1 diabetes. Treating diabetes-prone rodents with probiotics or antibiotics prevents the development of the disorder. Diabetes-prone rodents also have a distinctly different gut microbiome compared with healthy rodents. Recent studies in children with a high genetic risk for type 1 diabetes demonstrate significant differences in the gut microbiome between children who develop autoimmunity for the disease and those who remain healthy. However, the differences in microbiome composition between autoimmune and healthy children are not consistent across all studies because of the strong environmental influences on microbiome composition, particularly diet and geography. Controlling confounding factors of microbiome composition uncovers bacterial associations with disease. For example, in a human cohort from a single Finnish city where geography is confined, a strong association between one dominant bacterial species, Bacteroides dorei, and type 1 diabetes was discovered (Davis-Richardson et al. Front Microbiol2014;5:678). Beyond this, recent DNA methylation analyses suggest that a thorough epigenetic analysis of the gut microbiome may be warranted. These studies suggest a testable model whereby a diet high in fat and gluten and low in resistant starch may be the primary driver of gut dysbiosis. This dysbiosis may cause a lack of butyrate production by gut bacteria, which, in turn, leads to the development of a permeable gut followed by autoimmunity. The bacterial community responsible for these changes in butyrate production may vary around the world, but bacteria of the genus Bacteroides are thought to play a key role.

Mo1811 Clinical Remission Induced by Exclusive Enteral Nutrition (EEN) in Pediatric Crohn's Disease Is Associated With Microbiome Metabolic Changes Toward Increased Xenobiotic Biodegradation and Metabolism

esis of IBD, both Crohn's disease (CD) and ulcerative colitis (UC), is not well known. Most studies of human gut microbiota rely on the non-invasive collection of stool samples. However, the analysis of the fecal microbiota may not reflect the role of the mucosa-associated microbes which live in close proximity to the intestinal epithelium and that are in contact with the cells of the innate immune system directly involved in the inflammatory response. The aim of this study was to investigate the genotypes of Bacteroidetes microbiota from colon biopsies of IBD patients and to determine their relationship with the endoscopic activity of the disease. Methods: A prospective case-control study was designed. Colon biopsies from consecutive IBD patients and healthy controls (HC) (healthy subjects undergoing colonoscopy for colon cancer screening and having a healthy colon mucosa) were included. Inactive UC was defined as a Mayo endoscopic subscore of 0. Inactive CD was defined as a SES-CD score ≤ 2. Microbiota was characterized by using a restriction fragment length polymorphism (RFLP) analysis on PCR products targeting the 16SrRNA genes of Bacteroidetes digested with HinfI, PciI, DpnII and AciI. Results are shown as percentages. Results: 29 consecutive IBD patients (22 UC and 7 CD) and 15 HC were included. 8 patients presented with inactive UC (iUC) and 14 with active UC (aUC). All 7 CD patients presented with endoscopic activity (aCD). A total of 7 genotypes of Bacteroidetes called N1 and C1-C6 (of which N1 genotype is probably a strain of Bacteroides dorei and C1, and maybe C2, strains of B. vulgatus) were detected in all the biopsy samples analyzed. The number of genotypes present in biopsies from IBD patients was higher than that in HC, in whom only the N1 (66%) and C1 (34%) genotypes appear. While the presence of N1 genotypes was relatively constant in patients with active and inactive IBD, the percentage of C1 genotype in patients with aUC and aCD were very low (<5%) compared to controls. The C4 genotype never appeared in control samples and it was present in only 2% of iUC biopsies, whereas it was present in 15% and 16% of patients with aUC and aCD respectively. The C2, C5 y C6 genotypes appeared sporadically in biopsies of IBD with percentages of 1% in iUC (C2), 3% in aUC and 1% in aCD (C5), and 1% in iUC and aCD (C6), but never in HC. Conclusions: Bacteroidetes genotypes in colon biopsies differ between IBD patients and HC. These genotypes, and especially the C4 genotype, are highly specific for active IBD and further studies on their role on IBD pathogenesis are required.

Bacteroides dorei dominates gut microbiome prior to autoimmunity in Finnish children at high risk for type 1 diabetes.

The incidence of the autoimmune disease, type 1 diabetes (T1D), has increased dramatically over the last half century in many developed countries and is particularly high in Finland and other Nordic countries. Along with genetic predisposition, environmental factors are thought to play a critical role in this increase. As with other autoimmune diseases, the gut microbiome is thought to play a potential role in controlling progression to T1D in children with high genetic risk, but we know little about how the gut microbiome develops in children with high genetic risk for T1D. In this study, the early development of the gut microbiomes of 76 children at high genetic risk for T1D was determined using high-throughput 16S rRNA gene sequencing. Stool samples from children born in the same hospital in Turku, Finland were collected at monthly intervals beginning at 4–6 months after birth until 2.2 years of age. Of those 76 children, 29 seroconverted to T1D-related autoimmunity (cases) including 22 who later developed T1D, the remaining 47 subjects remained healthy (controls). While several significant compositional differences in low abundant species prior to seroconversion were found, one highly abundant group composed of two closely related species, Bacteroides dorei and Bacteroides vulgatus, was significantly higher in cases compared to controls prior to seroconversion. Metagenomic sequencing of samples high in the abundance of the B. dorei/vulgatus group before seroconversion, as well as longer 16S rRNA sequencing identified this group as Bacteroides dorei. The abundance of B. dorei peaked at 7.6 months in cases, over 8 months prior to the appearance of the first islet autoantibody, suggesting that early changes in the microbiome may be useful for predicting T1D autoimmunity in genetically susceptible infants. The cause of increased B. dorei abundance in cases is not known but its timing appears to coincide with the introduction of solid food.

The methylome of the gut microbiome: disparate Dam methylation patterns in intestinal Bacteroides dorei.

Despite the large interest in the human microbiome in recent years, there are no reports of bacterial DNA methylation in the microbiome. Here metagenomic sequencing using the Pacific Biosciences platform allowed for rapid identification of bacterial GATC methylation status of a bacterial species in human stool samples. For this work, two stool samples were chosen that were dominated by a single species, Bacteroides dorei. Based on 16S rRNA analysis, this species represented over 45% of the bacteria present in these two samples. The B. dorei genome sequence from these samples was determined and the GATC methylation sites mapped. The Bacteroides dorei genome from one subject lacked any GATC methylation and lacked the DNA adenine methyltransferase genes. In contrast, B. dorei from another subject contained 20,551 methylated GATC sites. Of the 4970 open reading frames identified in the GATC methylated B. dorei genome, 3184 genes were methylated as well as 1735 GATC methylations in intergenic regions. These results suggest that DNA methylation patterns are important to consider in multi-omic analyses of microbiome samples seeking to discover the diversity of bacterial functions and may differ between disease states.

Mucosa-associated bacteria in two middle-aged women diagnosed with collagenous colitis

To characterize the colon microbiota in two women histologically diagnosed with collagenous colitis using a culture-independent method. Biopsies were taken from the ascending colon and the total DNA was extracted. Universal bacterial primers were used to amplify the bacterial 16S rRNA genes. The amplicons were then cloned into competent Escherichia coli cells. The clones were sequenced and identified by comparison to known sequences. The clones could be divided into 44 different phylotypes. The microbiota was dominated by Firmicutes and Bacteroidetes. Seven phylotypes were found in both patients and constituted 47.5% of the total number of clones. Of these, the most dominating were clones similar to Bacteroides cellulosilyticus, Bacteroides caccae, Bacteroides thetaiotaomicron, Bacteroides uniformis and Bacteroides dorei within Bacteroidetes. Sequences similar to Faecalibacterium prausnitzii and Clostridium citroniae were also found in both patients. A predominance of potentially pathogenic Bacteroides spp., and the presence of clones showing similarity to Clostridium clostridioforme were found but the overall colon microbiota showed similarities to a healthy one. Etiologies for collagenous colitis other than an adverse bacterial flora must also be considered.

Intestinal Bacteroides species associated with coeliac disease

AimsTo characterise the predominant species of bacterial populations associated with duodenal biopsies of paediatric patients with active and treated coeliac disease.Methods20 biopsy specimens from patients with active coeliac disease, 12...

Bacteroides chinchillae sp. nov. and Bacteroides rodentium sp. nov., isolated from chinchilla (Chinchilla lanigera) faeces

Gram-negative anaerobic rods were isolated from chinchilla (Chinchilla lanigera) faeces and three strains, ST170(T), ST180 and ST28(T), were investigated taxonomically. On the basis of phylogenetic analyses and specific phenotypic characteristics, the three strains belonged to the genus Bacteroides. Phylogenetic analysis of their 16S rRNA gene sequences revealed that strains ST170(T) and ST180 formed a single cluster and a distinct line of descent. Strain ST170(T) exhibited 99.7 % 16S rRNA gene sequence similarity with strain ST180 and 95.1, 94.6 and 94.4 % 16S rRNA gene sequence similarity with Bacteroides massiliensis JCM 13223(T), Bacteroides dorei JCM 13471(T) and Bacteroides vulgatus JCM 5826(T), respectively. Strain ST28(T) also formed a distinct line of descent and exhibited the highest 16S rRNA gene sequence similarity with Bacteroides uniformis JCM 5828(T) (98.1 %). Low DNA-DNA relatedness (1 %) between strain ST28(T) and B. uniformis JCM 5828(T) clearly indicated that they belonged to different species. Analysis of hsp60 sequences also supported these relationships. The DNA G+C contents of strains ST170(T) and ST28(T) were 45.2 and 41.0 mol%, respectively. On the basis of phenotypic characteristics and phylogenetic data, two novel species, Bacteroides chinchillae sp. nov. (type strain ST170(T) = JCM 16497(T) = CCUG 59335(T)) and Bacteroides rodentium sp. nov. (type strain ST28(T) = JCM 16496(T) = CCUG 59334(T)), are proposed.

Isolation of bacteria from mouse caecal samples and description of Bacteroides sartorii sp. nov

Caecal samples from wild-type and TNF(deltaARE) mice were cultured on selective media containing bile salts, amino acids or casein macro-peptides. Twenty-two strains were isolated and identified by 16S rRNA gene sequencing. Twenty-one strains showed >98% similarity to known bacteria (Blautia spp., Clostridium innocuum, Enterococcus spp., Escherichia coli, Lactobacillus murinus, Parabacteroides goldsteinii and Shigella dysenteriae). One additional isolate, strain A-C2-0, was a new bacterium. The closest relatives were Bacteroides massiliensis, Bacteroides dorei and Bacteroides vulgatus (< or = 94% similarity). Strain A-C2-0 is a Gram-negative rod that does not form spores and has a G + C content of DNA of 41.5%. Its major cellular fatty acid is C(15:0 ANTEISO), and its major respiratory quinone is MK-9. Cells are aerotolerant but grow only under strict anoxic conditions. They are resistant to cefotaxime and tobramycin. When compared with related Bacteroides spp., the new bacterium was positive for alpha-arabinosidase, negative for glutamyl glutamic acid arylamidase and did not metabolise galactose, glucose, fructose, mannose, raffinose and sucrose. Strain A-C2-0 therefore merits recognition as a member of a novel species within the genus Bacteroides, for which the name Bacteroides sartorii is proposed. The type strain is A-C2-0(T) (= DSM 21941(T) = CCUG 57211(T)).

Characterization of the xylan-degrading microbial community from human faeces

In humans, plant cell wall polysaccharides represent an important source of dietary fibres that are digested by gut microorganisms. Despite the extensive degradation of xylan in the colon, the population structure and the taxonomy of the predominant bacteria involved in degradation of this polysaccharide have not been extensively explored. The objective of our study was to characterize the xylanolytic microbial community from human faeces, using xylan from different botanic origins. The xylanolytic population was enumerated at high level in all faecal samples studied. The predominant xylanolytic organisms further isolated (20 strains) were assigned to Roseburia and Bacteroides species. Some Bacteroides isolates corresponded to the two newly described species Bacteroides intestinalis and Bacteroides dorei. Other isolates were closely related to Bacteroides sp. nov., a cellulolytic bacterium recently isolated from human faeces. The remaining Bacteroides strains could be considered to belong to a new species of this genus. Roseburia isolates could be assigned to the species Roseburia intestinalis. The xylanase activity of the Bacteroides and Roseburia isolates was found to be higher than that of other gut xylanolytic species previously identified. Our results provide new insights to the diversity and activity of the human gut xylanolytic community. Four new xylan-degrading Bacteroides species were identified and the xylanolytic capacity of R. intestinalis was further shown.

Bacteroides dorei sp. nov., isolated from human faeces

Two Gram-negative, anaerobic, non-spore-forming rod-shaped organisms were isolated from human faeces. These isolates were tentatively identified as Bacteroides based on morphological and biochemical criteria and appeared closely related to Bacteroides vulgatus ATCC 8482(T). The 16S rRNA gene sequence analysis showed that the isolates were highly related to each other (99.5 %) and confirmed their placement in the genus Bacteroides. 16S rRNA gene sequence similarity values with close phylogenetic neighbours Bacteroides vulgatus ATCC 8482(T) (96 %) and Bacteroides massiliensis CCUG 48901(T) (93 %) preliminarily demonstrated that the organisms represented a novel species. The results of phenotypic, chemotaxonomic and 16S rRNA gene sequence analyses, and DNA-DNA homology values provided evidence that these two unknown isolates represent a single species and should be assigned to a novel species of the genus Bacteroides, as Bacteroides dorei sp. nov. The type strain is JCM 13471(T) (=DSM 17855(T)).