Chemically Induced Responses

Animals that have been intentionally exposed to specific pro-inflammatory or carcinogenic chemicals have been used in studies on the role of microbiota in the development of both cancer and IBD (Table 1). Cancer, or other malignant abnormalities in the gut mucosa, may be induced by the oral administration of carcinogens. Examples of such carcinogens are 1, 2 dimethylhydrazine (DMH), and N-methyl-N0-nitro-Nitrosogua-din (MNNG). These types of models, which are based on either CV or HFA animals,...

Comparison of the Models

The four colon simulation models presented here have structural and functional differences (Table 1), but the solutions used to reproduce the critical conditions that influence the microbiology of the colon are similar in all four models. Firstly the colonic microbiota is simulated in each model using fecal samples from a single donor or several donors in a pooled sample, because more realistic samples of gastrointestinal tract bacteria from the ileum or cecum of humans are very difficult to...

Possibilities and Limitations of Rumen Simulation Methods

The in vitro environmental conditions (temperature, pH, buffering capacity, osmotic pressure, dry matter content and oxidation-reduction potential) should represent as closely as possible those of the rumen. Irrespective of the technique applied, the quality of the inoculum is one of the most important aspects in rumen simulations. In most studies the rumen fluid is strained through two, sometimes even four layers of cheesecloth. As a result, the inoculum is likely to represent only the...

Crosstalk Between Bacteria And Intestinal Epithelial Cells

As discussed in chapter 5, some ingested probiotic bacteria have shown immunomodulatory properties (44-46). Both commensal and pathogenic bacteria possess recognized structures named pathogen-associated molecular patterns (PAMPS). These recognized structures are essential for the microbe, mostly constitutively expressed and shared by the same group of microorganisms. PAMPS that are characterized to date include N-formylated peptide (47), lipopolysaccharides (LPS) (48), and lipopeptides (49),...

Probing Strategies

As well as affording design of PCR primers for specific bacterial populations, the improved 16S rRNA gene sequence information has greatly enhanced the development of probing strategies for gut micro-organisms. Two probing strategies have generally been employed, namely, dot-blot hybridization and fluorescent in situ hybridization (FISH). The nature of the 16S rRNA gene of bacteria also enables development of oligonucleotide probes targeting different taxonomic levels, i.e., domain level (Bact...

Brief History Of The Development Of Bifidus Factors And Prebiotics

Bifidogenic or bifidus factors were recognized as early as 1954 with Gyorgy et al. (14,15) describing such components in milk and colostrum, including a range of amino sugars and non-glycosylated casein peptides. Glycoproteins from whey were also shown to have bifidogenic potential (16) along with lactoferrin (17,18). Bifidogenic effects have been reported for pantethine from carrot extracts (19,20) and for 2-amino-3-carboxy-1,4-naphthoquinone (ACNQ), a compound isolated from Propionibacterium...

Gnotobiotic Ruminants in Studies into the Microbiota of the Gastrointestinal Tract

Gnotobiotic ruminants can be used to observe the development of the rumen ecosystem as well as to study the relations between rumen and its microbiota. The rumen microbiota directly affects the development of the rumen epithelium and the level of intermediary metabolism by the action of rumen fermentation and its final metabolites. Fonty and coworkers (90), using meroxenic lambs demonstrated that the functions of the rumen and the stability of the ecosystem depended on the complexity and...

Types Of Intestinal Simulator Models

In vitro models can be divided into batch cultures, chemostat-type simulators, including semi-continuous and continuous cultures, and non-chemostat-type simulators. All models of the gastrointestinal tract (GIT) have strictly anaerobic conditions in order to simulate the environment that supports the growth of microbiota obtained from the GIT of humans or other mammals. In vitro models can be used sequentially, so that in the simulators of stomach and small intestine the food matrix can be...

Relationships Between The Intestinal Immune System And Intestinal Microbiota

The intestinal microbiota has marked influences on the intestinal and peripheral host's immunity. In some cases, the effects are produced by the whole intestinal microbiota, whereas in other cases only one predominant bacterium is capable of producing a certain immunostimulatory effect that is as effective as that of the whole microbiota. Moreover, the post-natal period seems to play a crucial role in the cross talk between the intestinal microbiota and the development of some important...

References

The human gastroinstestinal tract. In Brian JB Wood, ed. In Lactic Acid Bacteria, Vol. 1. London and New York Wood Publisher Elseivier Applied Science, 1992 69-114. 2. Hoskins LC. Mucin degradation in the human gastrointestinal tract and its significance to enteric microbial ecology. Eur J Gastroenterol Hepatol 1993 5 205. 3. Bry L, Falk PG, Midtvedt T, Gordon JI. A model of host-microbial interactions in an open mammalian ecosystem. Science 1996 273 1380-1383. 4. Ross MH, Kaye GI,...

Human Flora Associated Animals

The establishment of human fecal microbes within animals, provides the opportunity for the study of a microbiota of human origin within these animals. Human flora associated animals (HFA) have proven to be particularly valuable in studies of the metabolic and immunological activities of the human microbiota. Athough HFA animals are valuable for investigations related to the human microbiota, several differences between animal and human physiology may influence colonization by the human...

Bacterial Nitroreductase

Nitroreductase similar to azoreductase is exclusively of bacterial origin in the lumen of the intestine. The enzyme is required for the mutagenic activity of nitrocompounds (64). Nitroreductase generates reactive nitroso and N-hydroxyintermediates in the course of converting aromatic amines. 1-nitropyrene is formed by the reaction of nitrogen oxides with the combustion product pyrene. The presence of 1-nitropyrene in diesel exhaust makes exposure to this compound a real risk. 1-nitropyrene is...

Microbial Degradation of Intestinal Enzymes

In the following section, trypsin is used as a model substance for endogenously derived enzymes. It is excreted as a precursor, trypsinogen, from the pancreas, and activated in the small intestine, mainly by brush border enzymes (36). Fecal tryptic activity represents the net sum of processes involving the secretion of trypsinogen, its activation to trypsin, trypsin inactivators, and the presence in the intestine of microbial- and diet-derived compounds and enzymes that inactivate or degrade...

Rumen Simulators

The artificial rumen techniques developed over the past five decades for investigation of rumen physiology as well as evaluation of feed rations, have ranged from batch fermentations to more complicated continuous incubations. In addition, the absorption function of the rumen wall has been included in some designs, in which a semi-permeable membrane is applied for removal of the fermentation end products. The most simplistic, in vitro fermentations representing the rumen were performed in...

Elderly

The proposed benefits of prebiotics for the elderly have been based on early studies using culture methods that showed Bifidobacterium levels substantially decreased as a proportion of the total fecal microbiota in elderly Japanese, while the numbers of putrefactive bacteria such as clostridia increased 154 . These findings have only recently been re-addressed using modern bacteriological and molecular techniques, with mixed results. While a study from the United Kingdom 155,156 supported the...

Development Of Intestinal Microbiota In Dogs And Cats

Although there is paucity of research data concerning the development of intestinal microbiota of dogs and cats, it can be considered to follow a similar pattern as known for other mammals. Intestinal colonization is a gradual process starting immediately after birth. In newborn puppies and kittens the alimentary canal is sterile but is quickly inhabited by bacteria from birth canal and environment. The dam usually licks the newborn thoroughly thus transferring its own indigenous bacteria to...

Physiology and Microbiology of the GI Tract

The human GIT is the most appropriate environment to conduct studies on the human GI microbiota but for practical reasons animal models are used extensively for these types of studies. The wide range of similarities between the animal and human GIT makes it possible to draw reasonable parallels between these two hosts, however, results from studies on the human microbiota in animals may not entirely reflect processes occurring in the human GIT. The reason for this is that there are also many...

Advantages over Probiotics

With the exception of some mechanisms of immunomodulation, the theoretical basis for many of the anticipated probiotic effects of bifidobacteria rely on the bacteria being viable in the intestinal tract. Currently, probiotics are limited by their stability largely to fresh food products such as fermented dairy products and juices, and nutraceutical products where they are formulated as dried powders. In contrast, prebiotics are stable, can be heat-processed, and can therefore be incorporated...

Microbial Conversion of Cholesterol to Coprostanol

Cholesterol is a component in all mammalian cellular membranes and a precursor of steroid hormones, vitamin D, and bile acids. Pathophysiologically, it is thought to be an important factor in the pathogenesis of atheromatous arterial disease, hypertension, cancer of the large bowel, and other disorders 8 . The intestinal cholesterol is derived mainly from two sources partly from synthesis occurring in the liver and the small intestine and partly from foods of animal origin. The main elimination...

Age Altered Aspects of the Intestinal Microbiota

Normal aging is associated with significant changes in the function of most organs and tissues, such as decreased taste thresholds, hypochlorhydria due to atrophic gastritis, and decreased liver blood flow and size 11 . The GI tract is no exception, and there is increased evidence of impaired gastrointestinal function with aging 3,11-13 . In the GI tract of the elderly, the age-related changes include decreased acid secretion by the gastric mucosa, and greater permeability of mucosal membranes...

Features Of The Gastrointestinal Tract Structure and Function of the Small Intestine

Villi Diagram

The small intestine is the principal site of food digestion, nutrient absorption as well as endocrine secretion. It is the longest component of the alimentary tract, measuring over 6 meters, and is divided into three anatomic regions duodenum, jejunum and ileum. The duodenum begins at the pylorus of the stomach and is the proximal 20-25 cm of the small intestine. The jejunum spans about 2.5 meters in length. The ileum is approximately 3.5 meters long and an extension of the jejunum. The...

Taxonomic Species Placement of Bifidobacteria Microbiota with

Bifidobacteria have been known since Tissier 5 first described a species from the feces of breast-fed infants, which was later named as Lactobacillus bifidus by Orla-Jensen 29 . Since that time numerous studies have been published concerning the ecology and importance of bifidobacteria in the intestine of humans, especially in infants. A new taxonomic system was established by creating the genus Bifidobacterium with the description of several new species besides B. bifidum, which was the only...

Microbiota And Gastrointestinal System Distribution of Microbiota

The mucosal surface of the human body, including the gastrointestinal tract, the respiratory tract and the urogenital tract, has a total surface area of more than 400 m2 11 . The gastrointestinal tract's surface area is about 200-300 m2 and is colonized by 1013-14 bacteria with hundreds of bacterial species and subspecies. The normal microbiota of the gastrointestinal tract has been grouped and defined into two categories, the autochthonous indigenous and the allochthonous nonindigenous species...

Mucus Adhesion of Bifidobacteria

The reason for the age-related decrease in bifidobacteria numbers is still not well understood. Adhesion to the intestinal mucosa is regarded as a prerequisite for colonization by microbes and induction of the healthy promotion by them. It has therefore been proposed as one of the selection criteria for probiotic strains 42-45 . Ouwehand and coworkers 46 tested four Bifidobacterium strains for adhesion to mucus isolated from subjects of different age groups including healthy newborns, 2- and...

Info

Effect of carrageenan gel on formation of aberrant crypt foci Probiotics for reversal of hyperoxaluria Probiotics for inhibition of bacterial translocation Probiotics for chemically induced cancer Probiotics for improved gut permeability Probiotics for inhibition of bacterial translocation 2-Amino-3-methyl-3H -imidazo 4,5-f quinoline IQ. b 2-nitroflourene NF. c 2-Amino-alpha-carboline AAC. d Deficient in expression of Interfeukin 2 IL-2-. e Deficient in expression of Interleukin 10 IL-10-. f...

Microbial Bile Acid Metabolism

In all mammals, bile acids are derived from cholesterol in the liver. Cholic acid and chenodeoxycholic acid are common, but many other primary bile acids may be found. The primary bile acids are conjugated, usually with taurine or glycine, sometimes also with sulphate or glucuronate, and excreted into the bile. In the intestinal tract, the conjugated primary bile acids are attacked by microbial enzymes and converted into a variety of metabolites. The so-called secondary bile acids thus formed...

Structure and Function of the Large Intestine

Large Intestine Problems

The large intestine is a continuation of the ileum and is usually divided into three regions the colon, rectum and anal canal. The colon accounts for nearly the full length of the large intestine. The colon absorbs water and electrolytes approximately 1400 ml per day . It also compacts and eliminates feces about 100 ml per day . Feces are composed of water 75 , dead bacteria 7 , roughage 5 , inorganic substances 5 , and undigested protein, dead cells and bile pigment 1 . Bacterial products,...

Studies by Traditional Plate Culture Methods

The first reports associating allergy with characteristic microbial composition in the gut appear to be from studies in the former Soviet Union in the early1980s 38-40 . One of these studies, reported also in English, involved an assessment of 60 under one-year-old infants with food allergy and atopic eczema. It was claimed that the severity of the disease was in direct correlation with the stage of aberrancy in the fecal microbiota. This aberrancy was characterized as low prevalence of...

Fecal Samples

Feces are a complex microbial habitat, with many niches occupied by bacteria. It is estimated that bacteria account for about 30 of the fecal mass, and 40-55 of fecal solids. All of the bacteria in feces are exposed to the influences of dehydrating and concentrating mechanisms of the colon and rectum, and intense biochemical activity of the organisms living in the material. When the samples consist of only feces, the composition and localization of communities anywhere in the tract cannot be...

Preface

The human gastrointestinal tract microorganisms, termed the microbiota, have been investigated since the beginning of microbiological studies, when Antonie van Leeuwenhoek, the father of microbiology, investigated the microorganisms in his own stools. The human microbiota comprises trillions of microbes distributed in various niches throughout the intestinal tract and is one of the most complex microbial ecosystems on earth. The host and its microbiota have co-evolved together, and considering...

Bacterial Metabolism of Androgens and Estrogens

Estrone, estradiol, and estriol are the three major estrogens that are excreted into the bile. These estrogens are conjugated to glucuronic acid and or sulfate. Upon excretion of these conjugated estrogens from the bile into the small intestine the conjugates are available substrates for bacterial metabolism. The bacteria of the lower small intestine and colon can hydrolyze the estrogen conjugate releasing free estrogens 45 . The nonconjugated estrogens are then subject to additional bacterial...

Bacterial Metabolism of Tyrosine and Tryptophan

Tyrosine and tryptophan are amino acids that can be converted by bacterial reactions in toxins and carcinogens. The tryptophanase containing Bacteroides thetaiotamicron, an organism found in the intestine, can convert tryptophan to indole a compound with carcinogenic activity 75 . Tyrosine is converted to phenol by aerobic intestinal bacteria, and to p-cresol by intestinal anaerobic bacteria. These metabolites of tyrosine are not found in the urine of germfree mice. Phenol and cresol have been...

Anatomy

Lamina Propria Galt

The immune system associated with the small intestine is currently described according to two compartments i the inducing sites, named the gut associated lymphoid tissue GALT , consisting of organized aggregated lymphoid tissue, scattered small nodules, Peyer's patches PPs , and mesenteric lymph nodes MLN and ii the effector sites, i.e., the lamina propria tissue where numerous mature B and T small lymphocytes 60 CD4 T cells , plasma cells of which about 90 synthesize IgA are present, and the...

Proanthocyanidins

Proanthocyanidins are dimers, oligomers, and polymers of flavan-3-ols and are formed by enzymatic or chemical condensation. These so-called condensed tannins contribute to astringent tastes in fruits e.g., grapes, peaches, apples, pears, berries etc. , beverages e.g., wine, cider, tea, beer etc. and chocolate. At a lower degree of polymerization they are colorless and bitter to taste, but with greater polymerization the taste becomes astringent and the color yellow to brown. Proanthocyanidins...

Effects of Bifidobacteria Probiotics on Immunosenescence

Probiotics have been defined as a live microbial food ingredient that are beneficial to the health of the host 65,66 . Most current probiotics are lactic acid bacteria, especially Lactobacillus and Bifidobacterium species 66 . Among the proposed health-promoting effects of the probiotic strains are the enhancement of cell-mediated immune responses of the host by stimulating the pro-inflammatory cytokine, particularly IL-12 67,68 . The cell-mediated immune response, enhanced by the...

Biopsy

To investigate the gastric microbiota, tissue is generally obtained by an endoscopic biopsy. Slightly less invasive methods are available to obtain a specimen such as the use of a small bowel biopsy tube or capsule, or biopsy forceps that can be passed through a modified nasogastric tube positioned either in the gastric body or antrum. A biopsy is clinically unnecessary to diagnose H. pylori via microbiological methods unless one wishes to isolate the organism for antibiotic susceptibility...

Full Thickness Biopsy

Full thickness biopsy is a peroperative or laparoscopic biopsy muscularis-containing biopsy used to diagnose motility disturbances. One incision is situated below the umbilicus, and one in the left fossa. The bowel loop is identified laparoscopically, and will then be exteriorized through the incision below the umbilicus. The full thickness biopsy of at least 10X10 mm will then be taken with a surgical knife. The bowel loop is closed with absorbable sutures, and repositioned into the abdomen 56...

Intestinal Bacterial Metabolism of Bile Acids and Bile Pigments

Cholesterol is a precursor of bile acids, and both are synthesized in the liver from two carbon units. Bile acids synthesized in the liver are conjugated through an amide bond to either glycine or taurine. The conjugated bile acids are deposited in the bile, and excreted into the upper small intestine. The bacterial conversion of bile acids primarily occurs in the distal ileum and colon. The bacterial reactions on bile acids include the hydrolysis of the amide bond to release free bile acids...

Acquisition Of The Gut Microbiota

Acquisition of the normal microbiota is a biological succession which commences during or immediately following birth depending on the mode of delivery . During natural birth, the neonate is exposed to the maternal microbiota, both vaginal and fecal 22-24 . However, colonization is delayed in infants born via Caesarian section and the major source of inoculation is thought to be from the environment including nosocomially from within the maternity ward 23 . Caesarean section delivery has been...

Contributors

Akkermans Department of Surgery, Utrecht University Medical Center, Utrecht, The Netherlands Kaouther Ben Amor Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands Malik M. Anwar Alimentary Pharmabiotic Centre, Departments of Medicine and Surgery, Microbiology, National Food Biotechnology Centre, National University of Ireland, Cork, Ireland Max Bingham Unilever Research and Development, Vlaardingen, The Netherlands Alojz Bomba Institute of Gnotobiology and...

Glycocholate Breath Test

14C-glycocholate breath test or bile acid test is based on the bile salt deconjugating capacity of bacteria in the proximal small bowel. Conjugated bile acids are excreted through the bile in the duodenum, and they are reabsorbed in the terminal ileum. Conjugated bile acids are in the enterohepatic circulation. Physiologically, less than 5 of the conjugated bile acids reach the colon. After excretion in the duodenum, bile acids stimulate micellization of dietary lipids. After oral...

Colonization And Succession Of Human Intestinal Microbiota With

The gastrointestinal tract GI tract serves as one of the biggest interfaces between the body and the external environment 3 . This GI tract is a highly specialized organ system that allows us to consume food in discrete meals as well as a very diverse array of foodstuffs to meet our nutrient needs. The organs of the GI tract include the oral cavity, esophagus, stomach, small and large intestine in addition, the pancreas and liver secrete into the small intestine. The system is connected to the...