Sequence of Most-Common Gut Bacteria Completed

Researchers have completed sequencing the genome of Bacteroides thetaiotaomicron, one of the most common species of bacteria inhabiting the human intestine. The results appeared in the March 28, 2003, issue of Science.

"Now that the draft sequence of the human genome is complete, it is critical that we study the environmental forces that regulate our gene expression,” explained senior author Dr. Jeffrey I. Gordon, head of the department of molecular biology and pharmacology at the Washington University School of Medicine (St. Louis, MO, USA).

The human digestive tract is home to more than 1,000 different species of bacteria. Their collective genomes contain more than a hundred times more genes than does the genome of the human they are living in. These bacteria provide certain metabolic capabilities that humans lack, including the ability to process nutrients that human genes cannot break down.

The 4779-member proteome of B thetaiotaomicron includes an elaborate apparatus for acquiring and hydrolyzing otherwise indigestible dietary polysaccharides and an associated environment-sensing system consisting of a large repertoire of extra-cytoplasmic function sigma factors and one- and two-component signal transduction systems.

"This bacterium becomes prominent beginning at a key developmental transition that takes place when infants are weaned from their mother's milk and begin eating a diet rich in polysaccharides,” said Dr. Gordon.



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