Bacteroides thetaiotaomicron

A Microbial Biorealm page on the genus Bacteroides thetaiotaomicron

Classification

Higher order taxa

Bacteria; Bacteroidetes; Bacteroidetes (class); Bacteroidales; Bacteroidaceae

Species

Bacteroides thetaiotaomicron

Description and significance

Bacteroides thetaiotaomicron, a Gram negative anaerobic microbe, resides in and dominates the human intestinal tract . It consists of a 4776 member proteome containing the structural means to bring in and hydrolyze non-digestible polysaccharides as well as an environment sensing mechanism consisting of outer membrane proteins. Initially isolated from fecal matter, Bacteroides thetaiotaomicron has great importance in terms of the study of the symbiotic bacteria-host relationships within the human intestine as well as for its digestive abilities and potential breakdown of digested plants.

Genome structure

Bacteroides thetaiotaomicron consists of a 6.26 Mb genome containing 4776 genes that encode for 4776 proteins. The genome exists as one circular chromosome made of double stranded DNA. The GC content is 42.8% and 90% of the genome is involved in coding for proteins.

Additionally, Bacteroides thetaiotaomicron consists of one circular plasmid (p5482) which is 33,038 bp long, containing 38 genes coding for 38 proteins. The GC content of the plasmid is 47.2% and 83% of the genome is involved in coding for proteins. This 33 kb plasmid is one of several types of mobile genetic elements, including 63 transposases and four homologs of the conjugative transposon CTnDOT. The broad range of CTnDOT hosts as well as presence of CTn leads to the theory that microevolution could occur by means of DNA transfer between B. thetaiotaomicron and other forms of bacteria residing in the human gut.

Another interesting feature of B. thetaiotaomicron is that a large portion of its genome is involved in the harvesting and metabolizing of dietary polysaccharides. The co-localization of these genes involved in polysaccharide metabolism along with ECF-type sigma factors (important in sensing envoronmental cues) allow B. thetaiotaomicron to coordinate nutrient availability with expression of these specific genes.

Cell structure and metabolism

Bacteroides thetaiotaomicron is an anaerobic obligate parasite, which utilizes polysaccharides as its source of carbon and energy. An important step in the metabolism of the polysaccharide entails its binding to the cell surface before undergoing hydrolysis. This allows for the efficient sequesteration of hydrolysis products. Cell associated enzymes are responsible for hydrolyzing the polysaccharides into small fragments which are easily digestible. This binding and cleavage of the large substrate occurs either before or during translocation into the periplasm. The outer membrane associated multi-protein complex involved in this digestion process separates substrate binding and hydrolysis using different proteins for each task.

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Application to Biotechnology

Bacteroides thetaiomicron has been found to produce very high levels of a digestive enzyme seen to effective in the breakdown and subsequent digestion of plants, and thus has been a target for improvement of animal digestion. Modification of its activities would be a a good means to increase animal digestion of certain feed materials.