Researchers from the UW-Madison Genome Center announced Wednesday they have completely mapped the genome of a lethal strain of Escherichia coli, better known as E. coli.
A complete genomic map includes every gene, in this case about 4,800. The genes are made up of codons, each consisting of three base pairs of DNA. These pieces of DNA are then wound up into chromosomes and stored in the nucleoid region of the cell.
Out of hundreds of strains of E. coli, this strain, dubbed E. coli O157:H7, is the most lethal. In 1996, researchers from the Genome Center mapped the genomic sequence for a benign strain--E. coli k-12. Researchers expected to find differences between the strains, but essentially a similar genome. Instead, in a study to be published in the Jan. 25 issue of the journal Nature, they found stark differences.
\The sheer magnitude of the differences was totally shocking to us. We couldn't just zoom in on areas of difference between the two species. The changes were scattered throughout,"" researcher Nicole Perna, an assistant professor of animal health and biomedical sciences, said in a statement.
The most alarming discovery, according to researchers, is the new genome's ability to exchange sections of the genome across genera of bacteria such as Salmonella and the plague-causing bacteria Yersina.
""If the [exchanged section of DNA] is large enough, it could be an underlying factor in the emergence of a new disease,"" said Genome Center Director Fred Blattner, who also worked on the E. coli K-12 genome as well as E. coli O157:H7. ""We are already seeing this with the ability of some bacteria to develop antibiotic resistance. We need to be vigilant in finding the mechanisms that allow these pathogens to emerge.""
The discovery gives researchers ""far better distribution of genetic markers to help identify in the field,"" according to Perna.
Researchers believe this discovery makes a cure for the lethal bacteria likely.
The first reported incident of the food-born bacteria was in 1982, resulting from contaminated hamburger. E. coli lives in the intestines of cows, and if the meat is not properly handled during slaughter, the bacteria may be passed to supermarket shelves.
Other common sources of E. coli O157:H7 are sprouts, lettuce, salami, unpasteurized milk and juice and sewage contaminated water, according to the Centers for Disease Control and Prevention.
Chancellor John Wiley announced the discovery at his news conference Wednesday.
""It's a phenomenal breakthrough,"" Wiley said. ""It's the first step to basically curing [the infection].""
Vice Chancellor for Medical Affairs Phillip Farrell said Wiley has long been a major supporter of Blattner's research, particularly with regard to his work on completing the E. coli genome.
