Home » Escherichia coli (E. coli) Escherichia coli (E. coli) is a bacterium which is found normally in the lower intestine of warm-blooded animals. Strains possessing flagella can swim and are always motile, but other strains do not have flagella. The German bacteriologist and pediatrician, Theodor Escherich in 1885, discovered bacterium and E. coli is now classed as part of the Enterobacteriaceae family of gamma-proteobacteria.

Most of the strains of Escherichia coli (E. coli) are harmless, but some like serotype O157:H7 may cause severe food poisoning in human beings and are at times creditworthy for costly product recalls. The harmless strains are actually a part of the normal flora of the gut which can benefit their hosts by creating vitamin K2 or by forbidding the establishment of pathogenic bacteria inside the intestine.

Escherichia coli (E. coli) are always not confined to the intestine and their power to survive for brief periods out of the body makes them a favorable indicator organism in order to test environmental samples for the contamination of faeces. The bacteria possesses the capability to grow or can be grown easily and its genetics are relatively simple and are very easily manipulated, thus making it one of the best-studied and researched prokaryotic model organisms, and one of the major species in biotechnology. A strain of Escherichia coli (E. coli) is a sub-group within the species which possesses unique characteristics that differentiates it from other E. coli strains. These differences are usually detectable only on in the level of molecules. They may however result in changes to the lifecycle or physiology of the bacterium. For instance, a strain may acquire pathogenic capacity, the ability to inhabit a particular ecological niche, the ability to use a unique carbon source and the ability to resist antimicrobial agents. Various strains of E. coli are frequently host-specific, thus making it possible to ascertain the source of the contamination of faeces in environmental samples. Assumptions on whether the contamination originated from other mammal, a human or bird source can be made depending on which Escherichia coli strains are available in a water sample.

Newer strains of E. coli develop through the natural biological process of chromosomal mutation, and some strains evolve traits that may become harmful to a host animal. Even if virulent strains generally cause no more than a round of diarrhea in case of healthy adult humans, especially virulent strains, such as O111:B4 or O157:H7 can cause severe illness or even death in the older human beings, the very young or the immunocompromised.

Escherichia coli (E. coli) is facultative aerobic, Gram-negative and non-sporulating. It has the capacity to live on a wide range of substrates. E. coli utilizes mixed-acid fermentation in anaerobic conditions, thus producing lactate, ethanol, succinate, acetate and carbon dioxide. Many pathways in mixed-acid fermentation make hydrogen gas, these requires the hydrogen level to be low, so that E. coli can use them only if it lives with hydrogen-consuming organisms like sulfate-reducing bacteria or methanogens. The optimum growth of E. coli takes place at 37°C, but some laboratory strains can also multiply at up to 49°C.