Saccharomyces boulardii: Difference between revisions
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==Pathology== | ==Pathology== | ||
Although many have classified ''Saccharomyces boulardii'' as a non-pathogenic yeast, there have been evidence that ''S. boulardii'' is capable of acting as an opportunistic pathogen, causing ''Saccharomyces'' fungemia (15). Such cases have been identified as associations to yeast infection via inserted catheters (3). Other similar species, such as the ''Saccharomyces cerevisiae'', which is closely related to the pathogenic species, ''Candida'' is known to be an emerging opportunistic pathogen (10). It has been documented more frequently in the past decade the severity of cases of Saccharomyces fungemia, particularly with ''S. boulardii'' and ''S. cerevisiae'' (15). | |||
Patients who suffer from yeast allergies are not suggested to consume ''Saccharomyces boulardii'', since it has been found to cause worsened symptoms in patients with immunocompromised systems (9). | |||
==Application to Biotechnology== | ==Application to Biotechnology== | ||
Revision as of 19:09, 29 August 2007
A Microbial Biorealm page on the genus Saccharomyces boulardii
Classification
Higher order taxa
Domain (Superkingdom): Eukaryota
Kingdom: Fungi
Subkingdom: Dikarya
Phylum: Ascomycota
Subphylum: Saccharomycotina
Class: Saccharomycetes
Order: Saccharomycetales
Family: Saccharomycetacecae
Species
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NCBI: Taxonomy |
Genus species: Saccharomyces boulardii
Description and significance
Saccharomyces boulardii is a tropical strain of yeast, first isolated from lychee and mangosteen fruit from Indochina in 1934 by a French scientist by the name of Henri Boulard. Saccharomyces boulardii although similar to Saccharomyces cerevisiae, differs in its non-pathogenic and biotherapeutic features. It has been found to be an effective probiotic that combats a wide range of gastrointestinal disorders (see Biotechnology). S. boulardii have been found to be non-systemic, surviving only in the gastrointestinal tract at low pH levels, and capable of growth at temperatures up to 37°C (3). Saccharomyces boulardii is used in the treatment of a variety of gastrointestinal disorders, anti-biotic-associated diarrhea, nasogastric tube-associated diarrhea, diarrhea in both children and adults, and viral-infection associated diarrhea. It has also shown to weaken the effects of microbial disease caused toxins.
Genome structure
Although there has not been substantial research done on the genome structure of S. boulardii, this is partly due to the fact that it is nearly identical to that of S. cerevisiae. S. cerevisiae was the first eukaryotic genome to be completely sequenced. The completion of the genome was a result of a worldwide collaboration (23). The sequence contains 13,000,000 base pairs, 6,275 genes, 5885 of which are potential protein-encoding genes(23). Approximately 140 genes are strictly for specifying ribosomal RNA, 40 genes are for small nuclear RNA molecules and 275 function as transfer RNA genes (23). It has been observed that there is a significant quantity of redundancy. Approximately 23% of the genome is identical to the human genome (23). Chromosomes possess a single linear double stranded DNA (23).
Cell structure and metabolism
S. boulardii are oval cells with thick-walled cells which are approximately 10 µm long by 5 µm wide (24). The S. boulardii cell wall makes up approximately 30% of the dry weight of the cell and is primarily composed of polysaccharides (85%) and proteins (15%) (24). Extensive biochemical analyses reveal that glucose, N-acetylglucosamine (GlcNAc), and mannose residues represent 80 to 90%, 1 to 2%, and 10 to 20% of the total polysaccharide, respectively (24).
S. boulardii is classified as an anaerobe, meaning it can grow under aerobic or anaerobic conditions( 25). Although it prefers to use glucose, it is possible to use monosaccharides, polysaccharides, oligosaccharides, ethanol, acetate, glycerol, pyruvate, and lactate. Glucose goes through the glycolytic pathway for metabolism. S. bouldardii are heterotrophes, meaning they acquire their energy from glucose (25). S. boulardii prefers fermentation over respiration 98 to 2%, respectively (25). The fermentation pathway is known as Embden-Myerof Pathway (EMP) which yields products of ethanol (25). The consumption of glucose eventually will lead to a condition known as “cell depression”, which initiates oxidation of ethanol into carbon dioxide and water. Carbon sources which are non-fermentable must enter gluconeogenesis (25).
Saccharomyces boulardii acts as a shuttle to liberate enzymes, proteins, trophic factors during its intestinal transit to improve host immune defenses, digestion, and absorption of nutrients (5). S. boulardii is able to secrete polyamines (spermine and spermidine) during the intestinal transit to regulate gene expression hence, protein synthesis (5). S. boulardii relieves symptoms of intestinal injury and inflammation from an array of pathogens (6). In addition, S. bouldardii promotes the secretion of an antibody known as Immunoglobin A (IgA) in rat jejunum (located in small intestine). IgA’s are effective as defense to pathogenic microbes in the gastrointestinal and respiratory tracts (4).
Inflammation of the large intestine and sometimes small intestine is caused by the infiltration of T cells which aggregate in the lymph nodes. S. boulardii reduces inflammation by controlling and limiting T cell infiltration, specifically those T cells within the colon (14). Further research has suggested alternative methods of mechanism for the anti-inflammatory yeast. It was found that S. boulardii exerts anti-inflammatory effects by modulation of host cell signaling and pro-inflammatory gene expression. Specifically, the probiotic yeast is able to obstruct NF-kappaB activation and NF-kappaB-mediated IL-8 gene expression in the intestinal epithelial cells, resulting in the decrease of inflammation (6). In a separate study, researchers found that S. boulardii could also modulate the expression of PPAR-gamma. Stimulation of PPAR-gamma expression by S. boulardii results in a decrease in response of intestinal epithelial cells to proinflammatory cytokines (16).
Ecology
S. boulardii have been found to interact with a variety of microbes within the gastrointestinal tract of the human body. S. boulardii have been shown to reduce the concentration of diarrhea causing agents and their associated toxins (3). All types of diarrhea are effectively remedied by S. boulardii including acute diarrhea in adults, children, and infants (22), chronic diarrhea in AIDS patients (21), and diarrhea caused by bacterial infections.
S. boulardii has been utilized as a combatant to anti-biotic associated diarrhea, specifically with patients that suffer from Clostridium difficile (13). C. difficile infection is caused by anti-biotic treatments which eradicate the natural microflora in the lining of the gut causing inflammation to the colon and diarrhea (13). S. boulardii has been found to replenish a number of microflora in the digestive tract (13). C. difficile is an anaerobe which produces two toxins (A &B) responsible for nosocomial diarrhea in adults (13). Studies have found that S. boulardii decreases levels of C. difficile, however the most prominent effect is the reduction in concentration of C. difficile produced toxins, A and B (13). S. boulardii does so by releasing a 54-kDa protease that proteolytically digests toxin A and B and their brush border membrane receptors (13). In addition, S. boulardii inhibits C. difficile growth and has the ability to stimulate host mucosal activity to enhance the intestinal mucosal immune response (13).
S. boulardii is also effective at inhibiting the effects of Cholera, a condition caused by V. cholerae, a microbe which produces toxins that activate adenylate cyclase to stimulate cyclic AMP production, causing diarrhea (3). It was found that the mechanism of action involved a secretion of a protease known as 120 kDa which decreases the concentration of cholera-toxin induced cAMP in epithelial cells by inhibiting the stimulation of adenylate cyclase (12).
S. boulardii is an effective treatment for patients with inflammatory bowel disease (IBD). IBD is characterized by the common symptoms of abdominal pain, inflammation of the large intestine, disrupted intestinal transit, constipation or diarrhea, dyspepsia, and distension. Most of these symptoms are a result of an imbalance of microflora (18). S. boulardii treatment have been found to decrease all the symptoms of IBD (18).
S. boulardii decreases the quantity and severity of lesions developed by E. histolylica (3).
S. boulardii has been found to be an effective instrument in preventing the relapse of patients with Crohn’s Disease who have already achieved remission. Also, S. boulardii have been found to be advantageous in reducing the gastrointestinal symptoms and diarrhea associated with Ulcerative Collitis (7).
S. boulardii has also been shown to fight giardiasis, a condition caused by the bacteria, Giardia lamblia which coats the interior of the small intestine, cutting off nutrient absorption (22).
S. boulardii exhibits excellent anti-microbial effects, specifically against the pathogenic bacteria known as E.coli and S. typhi which cause acute infectious diarrhea. The mode of action known as mannose-sensitive adhesion involves the binding of the pathogenic bacteria to specific sites on the surface of S. boulardii by way of lectin receptors. Because of this irreversible adhesion, pathogenic bacteria are kept from invading the brush border, and conveniently excreted (19).
Bacterial enteropathogens such as the ones above are responsible for approximately 80% of all cases of Traveler’s Diarrhea (TD). Not only has S. boulardii proved to be an effective remedy for diarrhea, but studies have shown that consumption of S. boulardii as a preventative measure (taken 5-7 days prior to departure) decreases the risk of diarrhea (20).
S. boulardii has been found to effectively treat diarrhea associated with viral infections. Among the most studied is chronic diarrhea associated with the HIV virus (AIDS). S. boulardii was given to patients with Stage IV AIDS with the establishment of a control group receiving placebos. Dramatic improvements were seen only 18 months later, including an increase in body weight (whereas the condition of patients given placebos continued to deteriorate significantly) and a decrease of gastrointestinal symptoms (21).
Pathology
Although many have classified Saccharomyces boulardii as a non-pathogenic yeast, there have been evidence that S. boulardii is capable of acting as an opportunistic pathogen, causing Saccharomyces fungemia (15). Such cases have been identified as associations to yeast infection via inserted catheters (3). Other similar species, such as the Saccharomyces cerevisiae, which is closely related to the pathogenic species, Candida is known to be an emerging opportunistic pathogen (10). It has been documented more frequently in the past decade the severity of cases of Saccharomyces fungemia, particularly with S. boulardii and S. cerevisiae (15).
Patients who suffer from yeast allergies are not suggested to consume Saccharomyces boulardii, since it has been found to cause worsened symptoms in patients with immunocompromised systems (9).
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
Enter summaries of the most recent research here--at least three required
References
Edited by student of Rachel Larsen
