Bacteria Genomes - ESCHERICHIA COLI

E.coli is a normal inhabitant of the intestines of all animals, including humans. They are straight, rod-shaped, Gram-negative bacterium from the Enterobacteriaceae family

When aerobic culture methods are used, E.coli is the dominant species found in faeces. Normally E.coli serves a useful function in the body by suppressing the growth of harmful bacterial species and by synthesising appreciable amounts of vitamins. A minority of E.coli strains are capable of causing human illness by several different mechanisms.

Escherichia coli been implicated in many outbreaks of haemorrhagic colitis, some of which included fatalities caused by haemolytic uraemic syndrome. Close to 75,000 cases of E. Coli infection are now estimated to occur annually in the United States. The severity of disease, the lack of effective treatment and the potential for large-scale outbreaks from contaminated food supplies have propelled intensive research on the pathogenesis and detection of E. coli.

E. coli O157:H7 was first recognised as a cause of illness in 1982 and in 1996 there were nearly 9,000 victims and at least eight deaths, from an outbreak in Sakai city, Japan. The genome of E. coli O157:H7 has been sequenced to identify candidate genes responsible for pathogenesis, to develop better methods of strain detection and to advance our understanding of the evolution of E. coli, through comparison with the genome of the non-pathogenic laboratory strain E. coli K-12. Lateral gene transfer is far more extensive than previously anticipated. In fact, 1,387 new genes encoded in strain-specific clusters of diverse sizes were found in O157:H7. These include candidate virulence factors, alternative metabolic capacities, several prophages and other new functions-all of which could be targets for surveillance.

Strain RIMD 0509952 derived from this outbreak in Sakai city, Japan, in 1996 produces two kinds of verotoxins VT1 and VT2. In the EHEC strains, as well as in other VT-producing E. coli strains, the toxins are encoded by lysogenic bacteriophages. The EHEC O157:H7 strain RIMD 0509952 did not produce plaque-forming phage particles upon inducing treatments.

Strain RIMD 0509952 has been compared to strain EDL933 reported by Plunkett et al. (J. Bacteriol., p1767-1778, 181, 1999), although the sequences corresponding to the structural components are almost identical. These data suggest that these two phages were derived from a common ancestral phage and that either or both of them underwent multiple genetic rearrangements.

References:

http://genome.gen-info.osaka-u.ac.jp/bacteria/o157/
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/escherichiacoli_g.htm
Nature 409, 529 - 533 (2001)
DNA Res. 8:11-22(2001).
Genes Genet Syst. 1999 Oct;74(5):227-39.
Gene 2000 Nov 27;258(1-2):127-39
Department of Molecular Microbiology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.