Escherichia Coli (known as E. Coli) is a rod-shaped bacterium commonly found in the lower intestine of warm-blooded organisms. E. Coli brings to mind images of serious food poisoning in humans and massive produce recalls. However, most E. Coli strains are harmless. The harmless strains are part of the normal flora of the gut and can benefit the host by producing Vitamin K and by preventing the establishment of pathogenic bacteria within the intestine.
In 1885, Theodor Escherich, a German pediatrician, first discovered Escherichia and Salmonella in the feces of healthy individuals and called it Bacterium coli commune.
E. Coli cells are typically rod-shaped and are about 2 micrometers (um) long and 0.5um in diameter. Optimal growth of E. Coli occurs at 98.6°F (37°C), but some laboratory strains can multiply at temperatures up to 120°F (49°C).
E. Coli normally colonizes an infant's gastrointestinal tract within 40 hours of birth, arriving with food or water or with the individuals handling the child. In the bowel, it adheres to the mucus of the large intestine. As long as these bacteria do not acquire genetic elements encoding for virulence factors, they remain benign organisms that neither benefit, nor harm the other.