Degradation of intestinal glycoproteins byBacteroides vulgatus

Zearalenone-14-glucoside specifically promotes dysplasia of Gut-Associated Lymphoid Tissue: A natural product for constructing intestinal nodular lymphatic hyperplasia model

INTRODUCTION

Zearalenone-14-glucoside (Z14G) is a modified mycotoxin that widely contaminates food across the world. Our preliminary experiment showed that Z14G degrades to zearalenone (ZEN) in the intestine exerting toxicity. Notably, oral administration of Z14G in rats induces intestinal nodular lymphatic hyperplasia.

OBJECTIVES

To investigate the mechanism of Z14G intestinal toxicity and how it differs from ZEN toxicity. We conducted a precise toxicology study on the intestine of rats exposed to Z14G and ZEN using multi-omics technology.

METHODS

Rats were exposed to ZEN (5 mg/kg), Z14G-L (5 mg/kg), Z14G-H (10 mg/kg), and pseudo germ free (PGF)-Z14G-H (10 mg/kg) for 14 days. Histopathological studies were performed on intestines from each group and compared. Metagenomic, metabolomic, and proteomic analyses were performed on rat feces, serum, and intestines, respectively.

RESULTS

Histopathological studies showed that Z14G exposure resulted in dysplasia of gut-associated lymphoid tissue (GALT) compared to ZEN exposure. The elimination of gut microbes in the PGF-Z14G-H group alleviated or eliminated Z14G-induced intestinal toxicity and GALT dysplasia. Metagenomic analysis revealed that Z14G exposure significantly promoted the proliferation of Bifidobacterium and Bacteroides compared to ZEN. Metabolomic analysis showed that Z14G exposure significantly reduced bile acid, while proteomic analysis found that Z14G exposure significantly reduced the expression of C-type lectins compared to ZEN.

CONCLUSIONS

Our experimental results and previous research suggest that Z14G is hydrolyzed to ZEN by Bifidobacterium and Bacteroides promoting their co-trophic proliferation. This leads to inactivation of lectins by hyperproliferative Bacteroides when ZEN caused intestinal involvement, resulting in abnormal lymphocyte homing and ultimately GALT dysplasia. It is noteworthy that Z14G is a promising model drug to establish rat models of intestinal nodular lymphatic hyperplasia (INLH), which is of great significance for studying the pathogenesis, drug screening and clinical application of INLH.

Lead exposure induces structural damage, digestive stress, immune response and microbiota dysbiosis in the intestine of silver carp (Hypophthalmichthys molitrix)

Lead (Pb) is one of the most common trace metals in water, and its high concentration in the environment can cause harm to aquatic animals and humans. In the present study, the effects of Pb exposure (3.84 mg/kg) on the morphology, digestive enzyme activity, immune function and microbiota structure of silver carp (Hypophthalmichthys molitrix) intestines within 96 h were detected. Moreover, the correlation between them was analyzed. The results showed that Pb exposure on the one hand severely impaired the intestinal morphology, including significantly shortening the intestinal villi's length, increasing the goblet cells' number, causing the intestinal leukocyte infiltration, and thickening the intestinal wall abnormally, on the other hand, increasing the activity of intestinal digestive enzyme (trypsin and lipase). In addition, the mRNA expressions of structure-related genes (Claudin-7 and villin-1) were down-regulated, and the immune factors genes (IL-8, IL-10 and TNF-α) were up-regulated after Pb exposure. Furthermore, data of the MiSeq sequencing showed that the abundance of membrane transport, immune system function and digestive system of silver carp intestinal microbiota all decreased, while cellular antigens increased. Finally, the canonical correlation analysis (CCA) showed that there were correlations between silver carp's intestinal microbiota and intestinal morphology and immune factors. In conclusion, it is speculated that the entry of Pb into the intestine leads the microbiota dysbiosis, affects the intestinal immunity and digestive function, and further damages the intestinal barrier of silver carp.

Interactions between Blastocystis subtype ST4 and gut microbiota in vitro

BACKGROUND

Blastocystis ST4 is a common protistan parasite of the gastrointestinal tract of humans and a wide range of animals. While it has been suggested that colonization with ST4 is associated with healthy gut microbiota, how ST4 influences the gut microbiota remains poorly studied. This study aimed to examine the interactions between ST4 and several intestinal bacteria using in vitro co-culture systems, and to further investigate the mechanism of interaction and its effect on the epithelial barrier integrity of HT-29 cells.

METHODS

Seven intestinal bacteria Bacteroides fragilis, Bifidobacterium longum, Bacillus subtilis, Bacteroides vulgatus, Escherichia coli, Enterococcus faecalis, and Lactobacillus brevis were co-cultured with Blastocystis ST4 in vitro. Flow cytometry and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) were used to determine the role of reactive oxygen species (ROS) and bacteria oxidoreductase genes, respectively, in response to Blastocystis co-incubation. Transepithelial electrical resistance (TEER) and flux assays were performed to assess the effect of microbiota representatives on the integrity of the intestinal epithelial barrier.

RESULTS

Co-incubation with Blastocystis ST4 showed a beneficial influence on most intestinal bacteria, while ST4 significantly inhibited the growth of B. vulgatus, a common pathogen in the genus Bacteroides. The decrease in B. vulgatus when co-incubated with Blastocystis ST4 was associated with high levels of ROS and the upregulation of oxidative stress-related genes. Furthermore, co-incubation with Blastocystis ST4 was able to protect the intestinal epithelial barrier from damage by B. vulgatus.

CONCLUSIONS

This study demonstrated, for the first time, that Blastocystis ST4 has beneficial effects on intestinal commensal bacteria in vitro, and can inhibit the growth of pathogenic B. vulgatus. Combined with previous microbiome research on ST4, our data suggest that ST4 may be a beneficial commensal.

Sialylation and fucosylation modulate inflammasome-activating eIF2 Signaling and microbial translocation during HIV infection

An emerging paradigm suggests that gut glycosylation is a key force in maintaining the homeostatic relationship between the gut and its microbiota. Nevertheless, it is unclear how gut glycosylation contributes to the HIV-associated microbial translocation and inflammation that persist despite viral suppression and contribute to the development of several comorbidities. We examined terminal ileum, right colon, and sigmoid colon biopsies from HIV-infected virally-suppressed individuals and found that gut glycomic patterns are associated with distinct microbial compositions and differential levels of chronic inflammation and HIV persistence. In particular, high levels of the pro-inflammatory hypo-sialylated T-antigen glycans and low levels of the anti-inflammatory fucosylated glycans were associated with higher abundance of glycan-degrading microbial species (in particular, Bacteroides vulgatus), a less diverse microbiome, higher levels of inflammation, and higher levels of ileum-associated HIV DNA. These findings are linked to the activation of the inflammasome-mediating eIF2 signaling pathway. Our study thus provides the first proof-of-concept evidence that a previously unappreciated factor, gut glycosylation, is a force that may impact the vicious cycle between HIV infection, microbial translocation, and chronic inflammation.

Role of colonic microbiota in the pathogenesis of ulcerative colitis

BACKGROUND

Recent studies have found gut microbiota to be closely associated with onset and perpetuation of UC. Currently, studies about gut microbiota have mainly covered samples collected from the intestinal lumen. However, the luminal flora is only part of the gut microbiota. Studies of the changes in mucosal flora under pathological conditions have been lacking. In this study, we investigated the correlation between the onset of UC and flora changes in different intestinal layers.

METHODS

The dextran sulfate sodium(DSS)-induced UC model was established by exposing mice to cycles of DSS. The luminal contents, an inner mucus layer, and outer mucus layer were harvested under sterile conditions. The samples were then analyzed using high-throughput sequencing of 16S rRNA V3 + V4 amplicons. The colonic microbiota composition and diversity were analyzed and compared using MetaStat, LefSe, multivariate analysis of variance, and spatial statistics.

RESULTS

The DSS-induced UC mouse model was successfully established. The diversity of the microbiota from luminal content, the outer mucus layer, and inner mucus layer were significantly different in both control and UC model groups. The statistically different OTUs belonged to Lachnospiraceae and Ruminococcaceae families within the order Clostridiales were mainly localized to the outer mucus layer.

CONCLUSIONS

The alterations in flora composition and diversity mainly occurred in the colonic outer mucus layer. The change of flora in the colonic mucus layers is of great significance in the understanding of common features of gut flora in IBD and the understanding of the relationship between gut flora and disease progression.

Structural and mechanistic insights into a Bacteroides vulgatus retaining N-acetyl-β-galactosaminidase that uses neighbouring group participation

Bacteroides vulgatus is a member of the human microbiota whose abundance is increased in patients with Crohn's disease. We show that a B. vulgatus glycoside hydrolase from the carbohydrate active enzyme family GH123, BvGH123, is an N-acetyl-β-galactosaminidase that acts with retention of stereochemistry, and, through a 3-D structure in complex with Gal-thiazoline, provide evidence in support of a neighbouring group participation mechanism.

Identification of household bacterial community and analysis of species shared with human microbiome

Microbial populations in indoor environments, where we live and eat, are important for public health. Various bacterial species reside in the kitchen, and refrigerators, the major means of food storage within kitchens, can be a direct source of food borne illness. Therefore, the monitoring of microbiota in the refrigerator is important for food safety. We investigated and compared bacterial communities that reside in the vegetable compartment of the refrigerator and on the seat of the toilet, which is recognized as highly colonized by microorganisms, in ten houses using high-throughput sequencing. Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes were predominant in refrigerator and toilet samples. However, Proteobacteria was more abundant in the refrigerator, and Firmicutes was more abundant in the toilet. These household bacterial communities were compared with those of human skin and gut to identify potential sources of household bacteria. Bacterial communities from refrigerators and toilets shared more species in common with human skin than gut. Opportunistic pathogens, including Propionibacterium acnes, Bacteroides vulgatus, and Staphylococcus epidermidis, were identified as species shared with human skin and gut microbiota. This approach can provide a general background of the household microbiota and a potential method of source-tracking for public health purposes.

Dietary probiotic inclusion level modulates intestinal mucin composition and mucosal morphology in broilers

The aim of this study was to investigate the effect of dietary probiotic inclusion level on mucin composition (monosaccharide ratio), mucosal morphometry, mucus layer staining intensity, and mucus layer thickness along the broiler intestinal tract. One-day-old male Cobb broilers were administered maize-soybean meal basal (BD) diets for 42 d and depending on the feed additive used, broilers were allocated into the following 5 experimental treatments: control C (BD, no additive), treatment P1 (10(8) colony forming units of probiotic/kg of BD), treatment P2 (10(9) cfu of probiotic/kg of BD), treatment P3 (10(10) cfu of probiotic/kg of BD), and treatment A (2.5 mg avilamycin/kg of BD). Intestinal samples from duodenum, ileum, and cecum of 14- and 42-d-old broilers were collected and analyzed. Mannose (Man) decreased linearly with increasing probiotic level in duodenum (P=0.015) and ileum (P=0.042) of 14-d-old broilers. N-Acetyl-glucosamine and galactose decreased linearly (P=0.012 and P=0.001, respectively), while fucose increased linearly (P<0.001) with increasing probiotic feed inclusion level in 42-d-old broiler cecum, with treatment A not differing from treatment C (P≥0.05). Cecal villus height and crypt depth increased linearly (P=0.016 and P=0.003, respectively) with probiotic inclusion level, with treatment A having higher (P≤0.05) values only from treatment C. Mucus layer thickness increased linearly with probiotic inclusion level in duodenum at 14 d and 42 d (P=0.007 and P=0.030, respectively). Finally, mucus layer staining intensity was influenced (P<0.001) by villus fragment (i.e., tip, midsection, and base) but not from the treatment, age, and intestinal segment examined. As a conclusion, this study provides evidence that probiotic inclusion level affects intestinal mucin monosaccharide composition, mucus layer thickness, and intestinal morphology in broilers.

Mucin-bacterial interactions in the human oral cavity and digestive tract

Mucins are a family of heavily glycosylated proteins that are the major organic components of the mucus layer, the protective layer covering the epithelial cells in many human and animal organs, including the entire gastro-intestinal tract. Microbes that can associate with mucins benefit from this interaction since they can get available nutrients, experience physico-chemical protection and adhere, resulting in increased residence time. Mucin-degrading microorganisms, which often are found in consortia, have not been extensively characterized as mucins are high molecular weight glycoproteins that are hard to study because of their size, complexity and heterogeneity. The purpose of this review is to discuss how advances in mucus and mucin research, and insight in the microbial ecology promoted our understanding of mucin degradation. Recent insight is presented in mucin structure and organization, the microorganisms known to use mucin as growth substrate, with a specific attention on Akkermansia muciniphila, and the molecular basis of microbial mucin degradation owing to availability of genome sequences.

Molecular inventory of faecal microflora in patients with Crohn's disease

Intestinal microbial community is involved in the pathogenesis of Crohn's disease, but knowledge of its potential abnormalities has been limited by the impossibility to grow many dominant intestinal bacteria. Using sequence analysis of randomly cloned bacterial 16S ribosomal DNA, the dominant faecal species from four Crohn's disease patients and four controls were compared. Whereas marked inter-individual differences were observed in the faecal microflora of patients, three remained distantly related to controls on the basis of their operational taxonomic unit composition. Bacteroides vulgatus and closely related organisms represented the only molecular species shared by all patients and exhibited an unusually high rate of occurrence. Escherichia coli clones were isolated only in two patients with ileocolonic Crohn's disease. Moreover, numerous clones belonged to phylogenetic groups or species that are commonly not dominant in the faecal microflora of healthy subjects: Pectinatus, Sutterella, Verrucomicrobium, Fusobacterium, Clostridium disporicum, Clostridium glycolicum, Clostridium ramosum, Clostridium innocuum and Clostridium perfringens.

Patchy distribution of mucosal lesions in ileal Crohn's disease is not linked to differences in the dominant mucosa-associated bacteria: a study using fluorescence in situ hybridization and temporal temperature gradient gel electrophoresis

BACKGROUND

The mucosa-associated bacteria (MAB) are suspected of being involved in the pathogenesis of Crohn's disease. We analyzed and compared the MAB in noninflamed and inflamed ileal mucosa of Crohn's disease patients (n = 22).

METHODS

Tissue samples from the inflamed ileal mucosa and from the adjacent noninflamed ileal mucosa were taken from surgical resection specimens. The MAB were investigated using fluorescence in situ hybridization with 7 group-specific probes and temporal temperature gradient gel electrophoresis (TTGE).

RESULTS

Samples from both noninflamed and inflamed mucosa were obtained from 15 patients. The distribution of the bacterial populations was not different between noninflamed and inflamed mucosa. The Bacteroidetes phylum was dominant and accounted for 29% of MAB (0%-74%) in noninflamed tissues and 32% (0%-70%) in inflamed areas. The gamma Proteobacteria represented 12% (0%-70%) of MAB both in noninflamed and inflamed areas. The Clostridium coccoides group (Firmicutes phylum) represented 15% of MAB in noninflamed tissues versus 7% in inflamed areas. For most of the patients the similarity index between TTGE paired profiles was very high.

CONCLUSION

The dominant MAB do not differ between noninflamed and inflamed ileal mucosa in Crohn's disease. This argues against a localized dysbiosis to explain the patchy distribution of mucosal lesions.

Interleukin 10-deficient mice exhibit defective colonic Muc2 synthesis before and after induction of colitis by commensal bacteria

Germ-free (GF) interleukin 10-deficient (IL-10) mice develop chronic colitis after colonization by normal enteric bacteria. Muc2 is the major structural component of the protective colonic mucus. Our aim was to determine whether primary or induced aberrations in Muc2 synthesis occur in GF IL-10 mice that develop colitis after bacterial colonization. GF IL-10 and wild-type mice were colonized with commensal bacteria for various intervals up to 6 weeks. Colitis was quantified by histologic score and IL-12 secretion. Muc2 synthesis, total level of Muc2, and Muc2 sulfation were measured quantitatively. GF IL-10 mice showed 10-fold lower Muc2 synthesis and Muc2 levels compared with GF wild-type mice, but Muc2 sulfation was not different. When bacteria were introduced, IL-10 mice developed colitis, whereas wild-type mice remained healthy. Muc2 synthesis was unchanged in wild-type mice, but IL-10 mice showed a peak increase in Muc2 synthesis 1 week after bacterial introduction, returning to baseline levels after 2 weeks. Total Muc2 levels decreased 2-fold in wild-type mice but remained at stable low levels in IL-10 mice. Upon introducing bacteria, Muc2 sulfation increased 2-fold in wild-type mice, whereas in IL-10 mice Muc2 sulfation decreased 10-fold. In conclusion, a primary defect in colonic Muc2 synthesis is present in IL-10 mice, whereas bacterial colonization and colitis in these mice led to reduced Muc2 sulfation. These quantitative and structural aberrations in Muc2 in IL-10 mice likely reduce the ability of their mucosa to cope with nonpathogenic commensal bacteria and may contribute to their susceptibility to develop colitis.

The suppressive effect of bifidobacteria on Bacteroides vulgatus, a putative pathogenic microbe in inflammatory bowel disease

Bacteroides, a predominant commensal bacteria in the gut, are thought to be responsible for the development of inflammatory bowel disease (IBD). In the present study, we examined whether or not bifidobacteria suppress B. vulgatus, a representative pathogenic Bacteroides species, in both the coculture system and the gnotobiotic murine model. As a result, Bifidobacterium infantis 1222 highly inhibited the growth of B. vulgatus in the coculture and also significantly suppressed the systemic antibody response raised by B. vulgatus colonizing the gut in gnotobiotic mice. Colonization of the mice by B. vulgatus increased the number of Peyer's patch (PP) cells bearing PNA (peanut agglutinin)+/anti-kappa+ phenotype, which represents plasma cell-like B cells. Moreover, treatment of those B. vulgatus-implanted mice with B. infantis 1222 abrogated such increase in the number of PNA+/anti-kappa+ cells. These results thus suggested that B. infantis 1222 protected the gut epithelial layer including the PP from being invaded by Bacteroides, thereby suppressing the systemic antibody response raised by Bacteroides.

Potential probiotic lactic acid bacteria Lactobacillus rhamnosus (HN001), Lactobacillus acidophilus (HN017) and Bifidobacterium lactis (HN019) do not degrade gastric mucin in vitro

The mucus layer (mucin) coating the surface of the gastrointestinal tract (GIT) plays an important role in the mucosal barrier system. Any damage or disturbance of this mucin layer will compromise the host's mucosal defence function. In the present study, the ability of three potential probiotic lactic acid bacteria (LAB) strains (Lactobacillus rhamnosus HN001, Lactobacillus acidophilus HN017, Bifidobacterium lactis HN019) to degrade mucin in vitro was evaluated, in order to assess their potential pathogenicity and local toxicity. The LAB strains were incubated in medium containing hog gastric mucin (HGM, 0.3%) at 37 degrees C for 48 h, following which any decrease in carbohydrate and protein concentration in the ethanol-precipitated portion of the culture medium was determined, using phenol-sulphuric acid and bicinchonic acid (BCA) protein assays, respectively. The change in molecular weight of mucin glycoproteins, following incubation with the test strains, was monitored by SDS-polyacrylamide gel electrophoresis (SDS-PAGE). In order to expose any ability of the test strains to degrade mucin visually and more directly, the test strains were also cultured on agarose containing 0.3% HGM and incubated anaerobically for 72 h at 37 degrees C. No significant change in the carbohydrate or protein concentration in mucin substrates was found following incubation with the test strains. No mucin fragments were derived from the mucin suspension incubated with test strains, and no mucinolysis zone was identified on agarose. These results demonstrate that the potential probiotic LAB strains tested here were unable to degrade gastrointestinal mucin in vitro, which suggests that these novel probiotic candidates are likely to be non-invasive and non-toxic at the mucosal interface.

Inability of Lactobacillus casei strain GG, L. acidophilus, and Bifidobacterium bifidum to degrade intestinal mucus glycoproteins

BACKGROUND

Lactic acid bacteria have been suggested for use in the prevention of relapse of ulcerative colitis and of recurrent pouchitis. These strains may not damage the protective intestinal mucus glycoproteins.

METHODS

Lactobacillus casei strain GG and strains isolated from a commercial fermented product (Lactobacillus acidophilus, Bifidobacterium bifidum, and a mesophylic lactic culture) were cultured in vitro on hog gastric mucin and human intestinal glycoproteins. Furthermore, germ-free rats were mono-associated with Lactobacillus GG and poly-associated with the other strains. Glycoproteins were isolated from rat distal ileum, cecum, and colon. Mucus degradation was established by assaying carbohydrates (hexosamines, hexoses, pentoses), proteins, and blood group antigenicity.

RESULTS

All strains colonized the intestinal mucus but were not found in the deep crypts. Degradation of mucus glycoproteins was observed neither in vitro nor in vivo.

CONCLUSION

The tested strains do not break down intestinal mucus glycoproteins and thus far are safe to use for therapy.

Oral bacteriotherapy for viral gastroenteritis

The effect of orally administered lactobacilli on acute rotavirus diarrhea was tested in 42 well-nourished children ages 5-28 months. After oral rehydration, the patients were randomized to a study group, receiving human Lactobacillus casei strain GG 10(10) colony-forming units twice daily for five days, or a control group not given lactobacilli. Lactobacillus GG was found in the feces in 83% of the study group. The diarrheal phase was shortened in that group. Dietary supplementation with lactobacilli significantly influenced the bacterial enzyme profile: urease activity during diarrhea transiently increased in the control group but not in the study group; F = 8.6, P = 0.01. No intergroup differences were found in beta-glucuronidase, beta-glucosidase, and glycocholic acid hydrolase levels. We suggest that rotavirus infection gives rise to biphasic diarrhea, the first phase being an osmotic diarrhea and the second associated with overgrowth of specifically urease-producing bacteria. Oral bacteriotherapy appears a promising means to counteract the disturbed microbial balance.

Pouchitis: result of microbial imbalance?

To elucidate the role of microbiological factors in pouchitis, this study investigated the composition of ileal reservoir microflora, the mucus degrading capacity of bacterial enzymes as well as the pH and the proteolytic activity of pouch effluent. Stool samples were collected from five patients with pouchitis and nine patients without pouchitis. The flora of patients with pouchitis had an increased number of aerobes, a decreased ratio anaerobes to aerobes, less bifidobacteria and anaerobic lactobacilli, more Clostridium perfringens, and several species that were not found in control patients (for example, fungi). Furthermore the pH was significantly higher in patients with pouchitis (median value 6.5) than in control patients (5.4). To find out if the pH might influence the breakdown of intestinal mucus glycoproteins, the activity of glycosidases and proteases, and the degradation of hog gastric mucin by the pouch flora was tested at pH 5.2-7.6. Some glycosidases were inhibited, others were stimulated by a low pH, however, in each sample the proteolytic activity was inhibited for 75% at pH 5.2 compared with pH 6.8 and 7.6. Degradation of hog gastric mucin by the pouch flora was an active process at pH 7.2: within two to four hours of incubation more than half of the mucin was degraded. At pH 5.2 it took twice as long. It is concluded that pouchitis possibly results from instability of the flora in the pouch, which causes homeostasis to disappear (dysbiosis), and the protection of the pouch epithelium by the mucus layer becomes affected by increased activity of bacterial and host derived enzymes.

Changes in bacterial composition and enzymatic activity in ileostomy and ileal reservoir during intermittent occlusion: a study using dogs

Bacterial flora, activities of 10 potential mucus- and dietary polysaccharide-degrading enzymes, blood group antigenicity of the intestinal glycoproteins, and proteolytic activity in the output from experimentally colectomized dogs with conventional ileostomies and dogs with valveless ileal reservoirs (pouches) were determined. The ileostomies of dogs with conventional surgery (group II) and with pouches (group III) were occluded intermittently during a 6-week period. The duration of occlusion was progressively increased. Group I, five dogs with conventional ileostomies, served as a control group. After occlusion of the ileal pouch for 7 h, total numbers of bacteria increased threefold, glycosidase activity increased fivefold, and blood group antigenicity of the intestinal glycoproteins, which was high in the output from the nonoccluded pouch, was no longer detectable. Proteolytic activity was not influenced by occlusion of the pouch. Significantly lower numbers of bacteria, only minor glycosidase activity, high blood group antigenicities of the intestinal glycoproteins, and higher proteolytic activity were found in ileostomy effluents from groups I and II. Histopathological examination showed chronic inflammation and changes in crypt-villus ratio in all dogs with ileal reservoirs; the ileal mucosa from the dogs with conventional ileostomies did not show any abnormalities. Consequences of the flora-related enzyme activities for the ileal mucosa are discussed.