Escherichia Coli

The gut bacterium Escherichia coli has, for a variety of reasons, become a model organism for studying many of life's essential processes. Due to its rapid growth rate, simple nutritional requirements, well established genetics and completed genomes sequence, more is now known about E. coli than any other living organism. One property of this bacterium is its ability to grow in the absence of oxygen. This anaerobic growth is facilitated by the synthesis of enzymes which allow E. coli to use alternative compounds as electron acceptors. A number of these enzymes contain a complex metal cofactor, often the molybdopterin guanine dinucleotide (MGD) cofactor. Synthesis of this cofactor requires a number of steps, the last of which is incorporation the the nucleotide component . The proteins which catalyse this reaction are encoded by the mobAB locus which is being studies in the group of Dr. Tracy Palmer.

Another interesting feature of E. coli is that it can synthesise all its own amino acids, purines and pyrimidines using the nitrogen donor molecules glutamate and glutamine. The source of nitrogen for both these molecules is ammonium which E. coli preferentially uses as a nitrogen source. The transport of this key metabolite across the cytoplasmic membrane is being investigated in the lab of Dr. Mike Merrick.

(http://www.micron.ac.uk/Organisms/Ecoli/Ecoli.html)

Global properties:
  • Members of the genus Escherichia are common bacteria that colonize the human large intestine. Most are opportunistic normal flora but some are potent pathogens.
  • Transmission of diarrheal disease is generally person to person, usually related to hygiene, food processing and sanitation.
  • Four general categories of pathogenic E. coli are recognized:

Enterotoxigenic (ETEC)
Enteroinvasive or "Shigella-like" (EIEC)
Enteropathogenic (EPEC)
Enterohemorrhagic (EHEC)

  • Different groups are most often delineated by serology, in particular, by the immunogenic character of the O (somatic, LPS) and H (flagellar) antigens.

Distinctive properties:
  • Escherichia are Gram-negative bacilli that ferment lactose. Most are motile by peritrichious flagella.
  • Escherichia possess a typical Gram-negative cell wall containing LPS.
  • Approximately 170 different O antigens have been delineated and some of these are cross-reactive with Shigella, Salmonella and Klebsiella.
  • Motile strains possess H (flagellar) antigens that can be used for epidemiologic purposes.
  • Escherichia also possess K (capsular) antigens similar to the Vi antigen of Salmonella.
  • Enterotoxigenic strains may also display colonization factor antigens (CFA/I, CFA/II).

(http://www.cehs.siu.edu/fix/medmicro/esche.htm)

L'elephant et l'Escheria Coli, decembre 1972
"Tout ce qui est vrai pour le Colibacille est vrai pour l'elephant".

"Once we understand the biology of Escherichia coli, we will understand the biology of an elephant".

Jacques Monod.

(http://www.pasteur.fr/infosci/archives/mon/im_ele.html)

What does E.coli mean?

"E. coli is the abbreviated name of the bacterium in the Family Enterobacteriaceae named Escherichia (Genus) coli (Species). Dave Graham in the Department of Microbiology, University of Illinois at Urbana/Champaign, recently pointed me to information gleaned from G.W. Tannock's book, Normal Microflora,1995, Chapman & Hall, which reveals that approximately 0.1% of the total bacteria within an adult's intestines (on a Western diet) is represented by E. coli.

Although, in a newborn infant's intestines E. coli, along with lactobacilli and enterococci represent the most abundant bacterial flora. In fact, it is for this reason that the organisms which happily inhabit the intestinal tract as normal flora are named enteric bacteria. The Family to which E. coli belongs (Enterobacteriaceae, is named what it is - because of the Greek word enterikos - which pertains to the intestine. The name Escherichia comes from the name of the person Escherich, who in 1885 first isolated and characterized this bacterium..."

(http://people.ku.edu/%7Ejbrown/ecoli.html)