The Dynamic Distribution of Porcine Microbiota across Different Ages and Gastrointestinal Tract Segments

Metagenome of gut microbes has been implicated in metabolism, immunity, and health maintenance of its host. However, in most of previous studies, the microbiota was sampled from feces instead of gastrointestinal (GI) tract. In this study, we compared the microbial populations from feces at four different developmental stages and contents of four intestinal segments at maturity to examine the dynamic shift of microbiota in pigs and investigated whether adult porcine fecal samples could be used to represent samples of the GI tract. Analysis results revealed that the ratio of Firmicutes to Bacteroidetes from the feces of the older pigs (2-, 3-, 6- month) were 10 times higher compared to those from piglets (1-month). As the pigs matured, so did it seem that the composition of microbiome became more stable in feces. In adult pigs, there were significant differences in microbial profiles between the contents of the small intestine and large intestine. The dominant genera in the small intestine belonged to aerobe or facultative anaerobe categories, whereas the main genera in the large intestine were all anaerobes. Compared to the GI tract, the composition of microbiome was quite different in feces. The microbial profile in large intestine was more similar to feces than those in the small intestine, with the similarity of 0.75 and 0.38 on average, respectively. Microbial functions, predicted by metagenome profiles, showed the enrichment associated with metabolism pathway and metabolic disease in large intestine and feces while higher abundance of infectious disease, immune function disease, and cancer in small intestine. Fecal microbes also showed enriched function in metabolic pathways compared to microbes from pooled gut contents. Our study extended the understanding of dynamic shift of gut microbes during pig growth and also characterized the profiles of bacterial communities across GI tracts of mature pigs.     

Anatomy and histology of the gastrointestinal tract of the neo-tropical opossum (Didelphis marsupialis insularis,Allen 1902)

The morphology of the gastrointestinal tract (GI) is a strong indicator of the dietary habits of a species. The goal of this study was to describe the gross and microanatomy of the digestive tract of the neo-tropical opossum (Didelphis marsupialis insularis) and relate them to the animals’ food habits. GI tracts from 12 adult animals were used for this study. Results found the small intestine made up 65.9% of the GI tract, and the stomach was simple with a prominent caecum. Histologically, the oesophageal mucosa was non-keratinized and glands were found throughout the oesophagus. The large intestine showed a great number of goblet cells, the jejunum possessed well-developed villi, and Peyer's patches were absent in the ileum. The absence of keratinization of the epithelial lining of the oesophagus and stomach and a high lymphocytic infiltration throughout the small and large intestine reflected a more carnivorous diet, whereas the presence of a well-developed caecum in the large intestine indicated the ability to digest plant matter. Overall, the morphology of GI tract of D. m. insularis displayed both carnivorous and herbivorous features, allowing us to conclude that it is an omnivorous animal.     

Gut region induces gastrointestinal microbiota community shift in Ujimqin sheep (Ovis aries): from a multi-domain perspective

Gastrointestinal (GI) microbiota is one of the most complicated microbial ecosystems and is vital in regulating biological processes associated with nutrient absorption and homeostatic maintenance. Although several efforts have been achieved in characterizing bacterial communities across gut regions, the variation of non-bacterial communities across GI tracts is still largely unexplored. To address this, we investigated microbial biogeography throughout the whole GI tracts of Ujimqin sheep (Ovis aries) by amplicon sequencing which targeted bacteria, fungi, and archaea. The results indicated that the community structures of all three domains were significantly distinguished according to GI tracts (stomach, small intestine, and large intestine), and a more strong and efficient species interaction was detected in small intestine based on cross-domain network analysis. Moreover, a between-domain difference in microbial assembly mechanism of among-GI regions was revealed here, wherein bacterial community is dominantly governed by variable selection (explaining ~62% of taxa turnover), while fungal and archaeal communities mainly governed by homogenizing dispersal (explaining ~49% and 60% of the turnover, respectively). Overall, these data highlight the GI section- and domain-dependence of GI microbial structure and assembly mechanism, suggesting that multi-domain should be explicitly considered when evaluating the influences of GI selection on gut microbial communities.     

Spatial dynamics of the bacterial community structure in the gastrointestinal tract of red kangaroo (<Emphasis Type="Italic">Macropus rufus</Emphasis>)

The quantification and community of bacteria in the gastrointestinal (GI) tract (stomach, jejunum, ileum, cecum, colon and rectum) of red kangaroos (Macropus rufus) were examined by using real-time PCR and paired-end Illumina sequencing. The quantification of bacteria showed that the number of bacteria in jejunum and rectum was significantly lower than that in colon and cecum (P < 0.05). A total of 1,872,590 sequences was remained after quality-filtering and 50,948 OTUs were identified at the 97 % similarity level. The dominant phyla in the GI tract of red kangaroos were identified as Actinobacteria, Bacteroidetes and Firmicutes. At the level of genus, the samples from different parts of GI tract clustered into three groups: stomach, small intestine (jejunum and ileum) and large intestine (cecum and rectum). Prevotella (29.81 %) was the most dominant genus in the stomach and significantly (P < 0.05) higher than that in other parts of GI tract. In the small intestine, Bifidobacterium (33.04, 12.14 %) and Streptococcus (22.90, 19.16 %) were dominant genera. Unclassified Ruminococcaceae was the most dominant family in large intestine and the total relative abundance of unclassified bacteria was above 50 %. In identified genera, Dorea was the most important variable to discriminate large intestine and it was significantly higher in cecum than in stomach, small intestine and colon (P < 0.05). Bifidobacterium (21.89 %) was the only dominant genus in colon. Future work on culture in vitro and genome sequencing of those unidentified bacteria might give us insight into the function of these microorganisms in the GI tract. In addition, the comparison of the bacterial community in the foregut of kangaroos and other herbivores and the rumen might give us insight into the mechanism of fiber degradation and help us exploit approaches to improve the feed efficiency and subsequently, reduce the methane emission from herbivores.     

Spatial distribution and stability of the eight microbial species of the altered schaedler flora in the mouse gastrointestinal tract

The overall complexity of the microbial communities in the gastrointestinal (GI) tracts of mammals has hindered observations of dynamics and interactions of individual bacterial populations. However, such information is crucial for understanding the diverse disease-causing and protective roles that gut microbiota play in their hosts. Here, we determine the spatial distribution, interanimal variation, and persistence of bacteria in the most complex defined-flora (gnotobiotic) model system to date, viz., mice colonized with the eight strains of the altered Schaedler flora (ASF). Quantitative PCR protocols based on the 16S rRNA sequence of each ASF strain were developed and optimized to specifically detect as few as 10 copies of each target. Total numbers of the ASF strains were determined in the different regions of the GI tracts of three C.B-17 SCID mice. Individual strain abundance was dependent on oxygen sensitivity, with microaerotolerant Lactobacillus murinus ASF361 present at 10(5) to 10(7) cells/g of tissue in the upper GI tract and obligate anaerobic ASF strains being predominant in the cecal and colonic flora at 10(8) to 10(10) cells/g of tissue. The variation between the three mice was small for most ASF strains, except for Clostridium sp. strain ASF502 and Bacteroides sp. strain ASF519 in the cecum. A comparison of the relative distribution of the ASF strains in feces and the colon indicated large differences, suggesting that fecal bacterial levels may provide a poor approximation of colonic bacterial levels. All ASF strains were detected by PCR in the feces of C57BL/6 restricted flora mice, which had been maintained in an isolator without sterile food, water, or bedding for several generations, providing evidence for the stability of these strains in the face of potential competition by bacteria introduced into the gut.     

Pharmacokinetics of trefoil peptides and their stability in gastrointestinal contents

Trefoil factor family (TFF) peptides are considered promising for therapeutic use in gastrointestinal diseases, and there is a need to explore the fate of injected TFF and the stability of the peptides in the gastrointestinal tract. We studied the pharmacokinetics of intravenously (i.v.) administered hTFF2 in mice and rats and of hTFF3 administered i.v., intramuscularly, intraperitoneally, and subcutaneously in mice, and estimated by ELISA the decay of the peptides added to rat and human gastrointestinal contents. We found that i.v. injected hTFF2 and hTFF3 were cleared from the circulation within 2-3h, exhibiting comparable pharmacokinetic profiles. In contents from the rat stomach, hTFF levels remained unchanged for up to 6 days. In the small and large intestine of rats, the hTFF levels decreased markedly after 4 and 1h, respectively. In small intestinal contents from humans, the levels remained stable for more than 24h. We conclude that systemically administered hTFF2 and hTFF3 are rapidly eliminated from the circulation and that the stability of hTFF2 and hTFF3 in GI contents appeared higher in the gastric and small intestinal milieu than in the large intestine and feces, suggesting a higher stability toward gastric acid and digestive enzymes than toward microbial degradation.     

Immunohistochemical study of the gastrointestinal endocrine cells in the Korean aucha perch

The regional distribution and relative frequency of neurohormonal peptides‐producing cells were demonstrated in the gastrointestinal (GI) tract of the Korean aucha perch Coreoperca herzi , using 10 types of specific antisera raised against mammalian regulatory peptides. The GI tract was divided into four portions: stomach, gastro‐intestinal junction, and small and large intestine. Most of the immunoreactive (IR) cells were in the mucosal epithelium and they were generally spindle shaped with a long cytoplasmic process. In addition, ovoid cells were found in the gastric regions. Serotonin‐, somatostatin‐, glucagon‐, cholecystokinin‐8 (CCK‐8)‐ and pancreatic polypeptide (PP)‐IR cells were observed with various relative frequencies. No chromogranin A‐, secretin‐, vasoactive intestinal peptide‐, substance P‐ or bombesin‐IR cells, however, were found. Serotonin‐IR cells occurred throughout the GI tract and were the most numerous. Somatostatin‐IR cells were restricted to the stomach and gastro‐intestinal junction in numerous and moderate frequencies, respectively, but small numbers of glucagon‐IR cells were restricted to the small intestine. Numerous CCK‐8‐IR cells were found in the small intestine but variable numbers of PP‐IR cells occurred throughout the GI tract except for the large intestine. In general the distribution and relative frequency of these IR cells correspond well to previous reports in teleosts but there are some difference in this species.     

泽陆蛙消化道组织学观察

采用解剖学和组织学的方法对泽陆蛙消化道各部分的形态和组织学结构进行了观察。泽陆蛙的消化道分为口腔、咽、食道、胃、十二指肠、回肠和大肠。各管壁都由黏膜层、黏膜下层、肌层和外膜组成。食道黏膜层有皱褶和纤毛,无杯状细胞;胃黏膜层有杯状细胞和胃腺,黏膜下层有血管分布;小肠具绒毛、杯状细胞和肠腺,大肠皱褶少,杯状细胞也少。     

The fate of olive oil polyphenols in the gastrointestinal tract: implications of gastric and colonic microflora-dependent biotransformation

We have conducted a detailed investigation into the absorption, metabolism and microflora-dependent transformation of hydroxytyrosol (HT), tyrosol (TYR) and their conjugated forms, such as oleuropein (OL). Conjugated forms underwent rapid hydrolysis under gastric conditions, resulting in significant increases in the amount of free HT and TYR entering the small intestine. Both HT and TYR transferred across human Caco-2 cell monolayers and rat segments of jejunum and ileum and were subject to classic phase I/II biotransformation. The major metabolites identified were an O-methylated derivative of HT, glucuronides of HT and TYR and a novel glutathionylated conjugate of HT. In contrast, there was no absorption of OL in either model. However, OL was rapidly degraded by the colonic microflora resulting in the formation of HT. Our study provides additional information regarding the breakdown of complex olive oil polyphenols in the GI tract, in particular the stomach and the large intestine.     

The fate of olive oil polyphenols in the gastrointestinal tract: Implications of gastric and colonic microflora-dependent biotransformation

We have conducted a detailed investigation into the absorption, metabolism and microflora-dependent transformation of hydroxytyrosol (HT), tyrosol (TYR) and their conjugated forms, such as oleuropein (OL). Conjugated forms underwent rapid hydrolysis under gastric conditions, resulting in significant increases in the amount of free HT and TYR entering the small intestine. Both HT and TYR transferred across human Caco-2 cell monolayers and rat segments of jejunum and ileum and were subject to classic phase I/II biotransformation. The major metabolites identified were an O-methylated derivative of HT, glucuronides of HT and TYR and a novel glutathionylated conjugate of HT. In contrast, there was no absorption of OL in either model. However, OL was rapidly degraded by the colonic microflora resulting in the formation of HT. Our study provides additional information regarding the breakdown of complex olive oil polyphenols in the GI tract, in particular the stomach and the large intestine.     

Immunocytochemical localization of ornithine transcarbamylase in rat intestinal mucosa. Light and electron microscopic study

We investigated light and electron microscopic localization of ornithine transcarbamylase (OTC) in rat intestinal mucosa. In the immunoblotting assay of OTC-related protein, a single protein band with a molecular weight of about 36,500 is observed in extracts of liver and small intestinal mucosa but is not observed in those of stomach and large intestine. For light microscopy, tissue slices of the digestive system were embedded in Epon and stained by using anti-bovine OTC rabbit IgG and the immunoenzyme technique. For electron microscopy, slices of these and the liver tissues were embedded in Lowicryl K4M and stained by the protein A-gold technique. By light microscopy, the absorptive epithelial cells of duodenum, jejunum, and ileum stained positively for OTC, but stomach, large intestine, rectum, and propria mucosa of small intestine were not stained. Electron microscopy showed that gold particles representing the antigenic sites for OTC were confined to the mitochondrial matrix of hepatocytes and small intestinal epithelial cells. However, the enzyme was detected in mitochondria of neither liver endothelial cells, submucosal cells of small intestine, nor large intestinal epithelial cells. Labeling density of mitochondria in the absorptive epithelial cells of duodenum, jejunum, and ileum was about half of that in liver cells.     

Comparison between cultured small-intestinal and fecal microbiotas in beagle dogs

The microbiota of the small intestine is poorly known because of difficulties in sampling. In this study, we examined whether the organisms cultured from the jejunum and feces resemble each other. Small-intestinal fluid samples were collected from 22 beagle dogs with a permanent jejunal fistula in parallel with fecal samples. In addition, corresponding samples from seven of the dogs were collected during a 4-week period (days 4, 10, 14, and 28) to examine the stability of the microbiota. In the jejunal samples, aerobic/facultative and anaerobic bacteria were equally represented, whereas anaerobes dominated in the fecal samples. Despite lower numbers of bacteria in the jejunum (range, 10(2) to 10(6) CFU/g) than in feces (range, 10(8) to 10(11) CFU/g), some microbial groups were more prevalent in the small intestine: staphylococci, 64% versus 36%; nonfermentative gram-negative rods, 27% versus 9%; and yeasts, 27% versus 5%, respectively. In contrast, part of the fecal dominant microbiota (bile-resistant Bacteroides spp., Clostridium hiranonis-like organisms, and lactobacilli) was practically absent in the jejunum. Many species were seldom isolated simultaneously from both sample types, regardless of their overall prevalence. In conclusion, the small intestine contains a few bacterial species at a time with vastly fluctuating counts, opposite to the results obtained for the colon, where the major bacterial groups remain relatively constant over time. Qualitative and quantitative differences between the corresponding jejunal and fecal samples indicate the inability of fecal samples to represent the microbiotas present in the upper gut.     

Bacteria,phages and pigs: the effects of in-feed antibiotics on the microbiome at different gut locations

Disturbance of the beneficial gut microbial community is a potential collateral effect of antibiotics, which have many uses in animal agriculture (disease treatment or prevention and feed efficiency improvement). Understanding antibiotic effects on bacterial communities at different intestinal locations is essential to realize the full benefits and consequences of in-feed antibiotics. In this study, we defined the lumenal and mucosal bacterial communities from the small intestine (ileum) and large intestine (cecum and colon) plus feces, and characterized the effects of in-feed antibiotics (chlortetracycline, sulfamethazine and penicillin (ASP250)) on these communities. 16S rRNA gene sequence and metagenomic analyses of bacterial membership and functions revealed dramatic differences between small and large intestinal locations, including enrichment of Firmicutes and phage-encoding genes in the ileum. The large intestinal microbiota encoded numerous genes to degrade plant cell wall components, and these genes were lacking in the ileum. The mucosa-associated ileal microbiota harbored greater bacterial diversity than the lumen but similar membership to the mucosa of the large intestine, suggesting that most gut microbes can associate with the mucosa and might serve as an inoculum for the lumen. The collateral effects on the microbiota of antibiotic-fed animals caused divergence from that of control animals, with notable changes being increases in Escherichia coli populations in the ileum, Lachnobacterium spp. in all gut locations, and resistance genes to antibiotics not administered. Characterizing the differential metabolic capacities and response to perturbation at distinct intestinal locations will inform strategies to improve gut health and food safety.     

Comparative immunohistolocalization of carbonic anhydrase isozymes I, II and III in the equine and bovine digestive tract

Summary Immunohistochemical localizations of carbonic anhydrase isozymes (CA-I, CA-II and CA-III) in equine and bovine digestive tracts were studied. In the horse, epithelial cells in both the oesophagus and non-glandular part of the stomach lacked all three isozymes. In contrast, surface epithelial and parietal cells in the glandular region of the stomach showed reactivity for CA-II. In the small intestine, absorptive columnar cells covering the villi in the duodenum were positive for CA-II. The epithelium of the jejunum and ileum lacked all three isozymes. In the large intestine, CA-II was detected in the columnar cells in the upper part of the crypt. In cattle, epithelial cells of the oesophagus showed reactions for CA-I and CA-III but not for CA-II. Although the absorptive epithelial cells of the small intestine lacked CA-I, CA-II and CA-III, those of the upper part of large intestine crypts were heavily stained for all three isozymes.     

Abrupt temporal fluctuations in the chicken fecal microbiota are explained by its gastrointestinal origin

One of the main challenges in understanding the composition of fecal microbiota is that it can consist of microbial mixtures originating from different gastrointestinal (GI) segments. Here, we addressed this challenge for broiler chicken feces using a direct 16S rRNA gene-sequencing approach combined with multivariate statistical analyses. Broiler feces were chosen because of easy sampling and the importance for pathogen transmission to the human food chain. Feces were sampled daily for 16 days from chickens with and without a feed structure-induced stimulation of the gastric barrier function. Overall, we found four dominant microbial phylogroups in the feces. Two of the phylogroups were related to clostridia, one to lactobacilli, and one to Escherichia/Shigella. The relative composition of these phylogroups showed apparent stochastic temporal fluctuations in feces. Analyses of dissected chickens at the end of the experiment, however, showed that the two clostridial phylogroups were correlated to the microbiota in the cecum/colon and the small intestine, while the upper gut (crop and gizzard) microbiota was correlated to the lactobacillus phylogroup. In addition, chickens with a stimulated gizzard also showed less of the proximate GI dominating bacterial group in the feces, supporting the importance of the gastric barrier function. In conclusion, our results suggest that GI origin is a main determinant for the chicken fecal microbiota composition. This knowledge will be important for future understanding of factors affecting shedding of both harmful and beneficial gastrointestinal bacteria through feces.     

Immunohistochemical localization of Na+-dependent glucose transporter in the rat digestive tract

Summary Glucose is actively absorbed in the intestine by the action of the Na⁺-dependent glucose transporter. Using an antibody against the rabbit intestinal Na⁺-dependent glucose transporter (SGLT1), we examined the localization of SGLT1 immunohistochemically along the rat digestive tract (oesophagus, stomach, duodenum, jejunum, ileum, colon and rectum). SGLT1 was detected in the small intestine (duodenum, jejunum and ileum), but not in the oesophagus, stomach, colon or rectum. SGLT1 was localized at the brush border of the absorptive epithelium cells in the small intestine. Electron microscopical examination showed that SGLT1 was localized at the apical plasma membrane of the absorptive epithelial cells. SGLT1 was not detected at the basolateral plasma membrane. Along the crypt-villus axis, all the absorptive epithelial cells in the villus were positive for SGLT1, whose amount increased from the bottom of the villus to its tip. On the other hand, cells in the crypts exhibited little or no staining for SGLT1. Goblet cells scattered throughout the intestinal epithelium were negative for SGLT1. These observations show that SGLT1 is specific to the apical plasma membrane of differentiated absorptive epithelial cells in the small intestine, and suggest that active uptake of glucose occurs mainly in the absorptive epithelial cells in the small intestine.     

Islet amyloid polypeptide (IAPP) in the gastrointestinal tract and pancreas of man and rat

Summary An immunohistochemical study for islet amyloid polypeptide (IAPP) was made on the gastrointestinal (GI) tract and pancreas of man and rat, using antisera raised against a synthetic peptide of C-terminal human IAPP (24–37) and a synthetic peptide of rat IAPP (18–37). A large number of IAPP-immunoreactive cells were found in the pyloric antrum, and a small number in the body of the stomach in both man and rat. Cytoplasmic processes extended out from the bipolar peripheral region of the immunoreactive cells, rather like neuronal processes, and some appeared to make contact with other immunoreactive cells. In addition, small numbers of immunoreactive cells were also seen in the duodenum and rectum, whereas they were absent from the jejunum, ileum and large intestine. An examination was made for evidence of colocalization of IAPP-immunoreactive material with material immunoreactive for gastrin, somatostatin, vasoactive intestinal polypeptide, pancreatic polypeptide, insulin, and glucagon, but none was found. IAPP-immunoreactive cells were also found in the pancreas of non-diabetic and non-insulin-dependent diabetic patients, but they were completely absent from a patient with insulin-dependent diabetes mellitus despite the presence of IAPP in the plasma. The results of these studies suggest that the peptide may have a biological role in situ in the GI tract and, in addition to the pancreas, may be a possible source of plasma IAPP.     

Effective Recovery of Bacterial DNA and Percent-Guanine-Plus-Cytosine-Based Analysis of Community Structure in the Gastrointestinal Tract of Broiler Chickens

A DNA-based, direct method for initial characterization of the total bacterial community in ileum and cecum of the chicken gastrointestinal (GI) tract was developed. The efficiencies of bacterial extraction and lysis were >95 and >99%, respectively, and therefore the DNA recovered should accurately reflect the bacterial communities of the ileal and cecal digesta. Total bacterial DNA samples were fractionated according to their percent G+C content. The profiles reflecting the composition of the bacterial community were reproducible within each compartment, but different between the compartments of the GI tract. This approach is independent of the culturability of the bacteria in the consortium and can be used to improve our understanding of how diet and other variables modulate the microbial communities of the GI tracts of animals.     

黑眶蟾蜍和黑斑蛙消化道5-羟色胺免疫活性细胞的免疫组织化学

对黑眶蟾蜍（Bufo melanostictus）和黑斑蛙（Rana nigromaculata）消化道5-羟色胺免疫活性细胞的形态、分布进行了免疫组织化学定位。5-羟色胺免疫活性细胞在黑眶蟾蜍和黑斑蛙消化道各段中均有分布,分布密度均呈升-降-升-降的波浪式分布特点,二者在幽门部和回肠都有个分布的高峰值。黑眶蟾蜍回肠最高,空肠、幽门部次之,十二指肠、直肠最低;黑斑蛙幽门部最高,回肠、空肠次之,食道、贲门部、直肠最低。5-羟色胺免疫活性细胞位于胃的胃腺上皮、食道及肠的粘膜上皮,有圆形、椭圆形、梭形、楔形等,有的有胞突。文中讨论了5-羟色胺免疫活性细胞分布型的原因及形态与功能的关系。