Bacteroides thetaiotaomicron VPI-5482

Names Bacteroides thetaiotaomicron VPI-5482
Accession numbers NC_004663, NC_004703
Background Bacteroides are commonly found in the human intestine where they have a symbiotic host-bacterial relationship with humans. They assist in breaking down food and producing valuable nutrients and energy that the body needs. However, when Bacteriodes are introduced to parts of the body other than the gastrointestinal area, they can cause or exacerbate abscesses and other infections.Bacteroides are gram-negative, nonsporeforming, anaerobic, and rod-shaped bacteria. They have an outer membrane, a peptidoglycan layer, and a cytoplasmic membrane. The main by-products of their anaerobic respiration are acetic acid, iso valeric acid, and succinic acid. They are involved in many important metabolic activities in the human colon including fermentation of carbohydrates, utilization of nitrogenous substances, and biotransformation of bile acids and other steroids. Most intestinal bacteria are saccharolytic, which means that they obtain carbon and energy by hydrolysis of carbohydrate molecules.It is estimated that only about 2% of simple sugars make it past the upper gastrointestinal tract and to the Bacteroides. Thus, simple sugars are probably not Bacteroides main source of energy. However, polysaccharides from plant fibers, such as cellulose, xylan, arabinogalactan, and pectin, and vegetable starches such as amylose and amylopectin, are much more prevalent in the colon. These polysaccharides have also been shown to induce a variety of glucosidase activities from Bacteroides including a b-1,3-glucosidase activity responsible for laminarin degradation and a variety of a and b-1,4 and -1,6 xylosidase and glucosidase activities. A large part of the Bacteroides 4779-member proteome incudes proteins that hydrolyze these polysaccharides (Jian et al. 2003).Bacteroides thetaiotaomicron have been shown to bind to polysaccharides with their outer membrane receptor system (the outer membrane can be seen in the picture to the right) before pulling the polysaccharides into the periplasm for monosaccharide degradation. This technique may help insure that the polysaccharides are not stolen by other intestinal organisms or lost in the intestines by diffusion. Bacteroides polysaccharide utilization genes are thought to be controlled by repressor/inducer mechanisms.Although Bacteroides are gram-negative, as are most bacteria in the human colon, and live in the same environment as E. coli, the two bacteria are actually less closely related than Bacteroides are to gram-positive bacteria. The Bacteroides definition has specific criteria, some of which are as follows: obligately anaerobic, gram-negative, saccharolytic, contain enzymes of the hexose monophosphate shunt-pentose phosphate pathway, have a DNA-base composition of about 40-48% G-C, and membranes contain a mixture of long-chain fatty acids, mainly straight chain saturated, anteiso-methyl, and iso-methyl branched acids.Anaerobes make up the majority of bacteria found in the bacterial flora found in the human colon; the most predominant bacteria found are Bacteroides. The colon contains over 400 species of organisms and has more than 1,011 organisms per gram of wet weight. Bacteroides by themselves constitute nearly 1,011 organisms per gram of feces (dry weight). It is clear that these anaerobes, by assisting in processing complex molecules and metabolic pathways, are necessary for the proper health of their human host. Anaerobes, such as Bacteroides, are though to play a fundamental role in this ecosystem by processing complex molecules into simpler compounds. (These simpler compounds are used by the human host as well as the Bacteroides.) Other than the ability to use polysaccharides into useable compounds (which might allow it to be more competitive than bacteria that must rely on other sources of energy), it is not clear why Bacteroides are more prevalent than most other gastrointestinal bacteria. (From (MicrobeWiki: Bacteroides)
Strain VPI-5482
Complete Yes
Sequencing centre (28-MAR-2003) National Center for Biotechnology Information, NIH, Bethesda, MD 20894, USA
(31-OCT-2002) Department of Molecular Biology and Pharmacology, Washington University in St. Louis, 660 S. Euclid,
Sequencing quality Level 6: Finished
Sequencing depth NA
Sequencing method Sanger
Isolation site Feces of a healthy adult
Isolation country NA
Number of replicons 2
Gram staining properties Negative
Shape Bacilli
Mobility No
Flagellar presence No
Number of membranes 2
Oxygen requirements Anaerobic
Optimal temperature NA
Temperature range Mesophilic
Habitat HostAssociated
Biotic relationship Free living
Host name Homo sapiens
Cell arrangement NA
Sporulation NA
Metabolism NA
Energy source NA
Diseases Opportunistic peritoneal diseases
Pathogenicity No