After staining, Escherichia coli appears as short rods, with some individual bacteria showing approximately spherical-rod or filamentous shapes. Escherichia coli can be stained red or pink by Gram staining.

The normal resident bacteria in the animal intestines are Escherichia coli, and in some cases, only a very few can cause disease. Gastrointestinal infections are mainly caused by infections of the gastrointestinal tract, leading to gastrointestinal infections in humans or animals. In addition to causing gastrointestinal infections, Escherichia coli can also cause urinary tract infections, arthritis, meningitis, septicemia, and other infections.

Escherichia coli is a type of bacteria belonging to the prokaryotes, with a cell wall composed of peptidoglycan, containing only a simple ribosome, without a nucleus or nucleoid, and is often used as a vector in genetic engineering. The metabolic type of Escherichia coli is heterotrophic and anaerobic, and does not require the addition of growth factors in the culture medium. When E. coli is added to the culture medium with Eosin Methylene Blue, it appears deep purple with metallic luster, which can be used to identify the presence of Escherichia coli.