E. coli is a bacterium that is commonly found in the lower intestine of warm-blooded animals. It is also known as Escherichia coli. E. coli is part of the normal gut flora, but can also cause food poisoning if ingested.
The name “Escherichia” comes from German scientist Theodor Escherich, who first isolated the bacteria in 1885. “Coli” comes from the Greek word for colon (κολπός).
E. coli are rod-shaped bacteria that are about 2 micrometers long and 0.5 micrometers wide. They are motile, meaning they can move around, and have flagella (whip-like structures) that help them to do so. E. coli are Gram-negative, meaning they have a thin layer of peptidoglycan between their cell membrane and their nucleus. This makes them more susceptible to antibiotics than Gram-positive bacteria, which have a thicker peptidoglycan layer.
Most strains of E. coli are harmless, and even beneficial to humans; however, some strains can cause serious illness or even death if ingested (for example, by contaminated food or water). These pathogenic strains typically produce toxins that damage the lining of the intestinal wall, causing bloody diarrhea and abdominal cramps (known as hemolytic uremic syndrome). In severe cases, this can lead to kidney failure and death. Some pathogenic strains of E..coli also produce Shiga toxins; these toxins bind to receptors on mammalian cells and cause them to die (a process known as apoptosis). Shiga toxin–producing E..coli (STEC) infections can lead to severe bloody diarrhea (hemorrhagic colitis), which can be life-threatening if not treated promptly with fluids and antibiotics