Escherichia coli
Escherichia coli, also known as E. coli, is a bacterium commonly found in the intestinal tract of humans and animals. Although most strains of E. Coli are harmless, some can cause serious illness.
Discovery of Escherichia coli
E.coli is one of the most studied bacteria in the world. Since its discovery in 1885, scientists have learned much about its biology and its importance in human health. E. Coli is an indicator of food and water hygiene and is often used to determine if food and water are contaminated with fecal matter.
Morphology
E. coli is a Gram-negative, facultative anaerobe, nonsporulating coliform bacterium. Cells are typically rod-shaped, and are about 2.0 μm long and 0.25 – 1.0 μm in diameter, with a cell volume of 0.6 – 0.7 μm3. Antibiotics can effectively treat E. coli infections outside the digestive tract and most intestinal infections but are not used to treat intestinal infections by one strain of these bacteria. The flagella which allow the bacteria to swim have a peritrichous arrangement. It also attaches and effaces to the microvilli of the intestines via an adhesion molecule known as intimin.
Most strains do not cause disease in humans and are part of the normal microbiota of the gut; such strains are harmless or even beneficial to humans although these strains tend to be less studied than the pathogenic ones. For example, some strains of E. coli benefit their hosts by producing vitamin K2 or by preventing the colonization of the intestine by pathogenic bacteria. These mutually beneficial relationships between E. coli and humans are a type of mutualistic biological relationship — where both the humans and the E. coli are benefitting each other. E. coli is expelled into the environment within fecal matter. The bacterium grows massively in fresh faecal matter under aerobic conditions for three days, but its numbers decline slowly afterwards.
E. coli and other facultative anaerobes constitute about 0.1% of gut microbiota, and fecal–oral transmission is the major route through which pathogenic strains of the bacterium cause disease. Cells are able to survive outside the body for a limited amount of time, which makes them potential indicator organisms to test environmental samples for fecal contamination. A growing body of research, though, has examined environmentally persistent E. coli which can survive for many days and grow outside a host.
Symptoms
E. coli can be a pathogenic bacterium, that is, it can cause disease in humans. Some strains of E. Coli produce toxins that can cause diarrhea, abdominal pain, and vomiting. The disease is known as urinary tract syndrome, or UTI, and is most common in young children, older people, and people with weakened immune systems.
E. coli can also cause blood infections, which can be life-threatening. These infections occur when bacteria enter the bloodstream through lesions on the skin or gastrointestinal tract. Sepsis, a serious illness that can cause organ damage and death, is a potential complication of E-blood infection.
E. Coli uses
Despite its potential negative effects on human health, E. coli can also be a useful bacterium. Scientists have used E. coli to developed techniques to manipulate their DNA. E. Coli is also used in the production of food and pharmaceuticals, such as insulin used in the treatment of diabetes.

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