Escherichia coli

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Escherichia coli (E. coli) is a gram negative bacterium commonly found in the intestinal tracts of animals. It is capable of growing and metabolising glucose both in external aerobic conditions or environments, as well as in internal anaerobic conditions such as the gastrointestinal tract of warm-blooded animals[1]. E. coli thrives in the intestines of animals both in health and disease. It aids in the process of digestion, helps in the absorption of many important nutrients required by the body, and protects the gastrointestinal tract from various harmful bacteria[2]. Most strains of E. coli are harmless, while other strains may produce toxins that can cause various types of diseases in humans, such as for example E. coli 0157 which can be a serious cause of gastroenteritis[3][4].

Specific types of gram-negative have evolved rapidly their resistance to antibiotics

E. coli has a circular chromosome which means that when it is replicated, this happens bidirectionally from the Origin of Replication (OriC) to the terminus (terC.) E. coli therefore has two replication forks.

The chromosome replicates at ~850 bases per second per replication fork. It takes only 40 minutes to replicate the whole chromosome and the cell with then divide 20 minutes after replication is complete[5].

In many microbiology studies E. coli is often used as a model organinsm in lab experiments, serving as an experimental tool in order to understand how other organisms function and react to certain situations. It is a commonly used model organism due to its fast reproduction time, how easily it is manipulated and its already sequenced genome. The E. coli strain K-12 is the strain most commonly used in the laboratory. It has 4.6 million nucleotide pairs in its genome that code for approximately 4300 different proteins[6]. Two different strains of E. coli could have as few as half of their genes in common.

E. coli was discovered by Theodore Escherich and is responsible for causing various different diseases. E. coli has many virulence factors and extrachromosomal plasmids may contain virulence proteins[7]. Many of these extrachromosomal plasmids will have been obtained by horizontal gene transfer. The primitive genetic mechanisms of E. coli have been highly conserved which makes it a very good laboratory model[8].


  1. Todar,K. Pathogenic E. coli [online] in:
  2. Hu, A. Looks can be deceiving: the case of Escherichia coli [online] in:
  3. Pennington, H. Escherichia coli 0157 [online] in:
  4. Harrison, K. Types of Diseases caused by E. coli [online] in:
  5. Griffiths AJF, Miller JH, Suzuki DT, et al. (2000) An Introduction to Genetic Analysis. 7th Edition
  6. Alberts. B, Johnson A, Lewis. J, Raff. M, Roberts. K, Walter. P, (2008), Molecular Biology Of The Cell, fifth edition, Garland Science, Taylor and Francis Group, New York, p25
  8. Alberts B., Johnson A., Lewis J. Molecular biology of the cell.(2008) Garland Science. 5th edition.
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