 E. coli is a gram-negative, facultative anaerobic (that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent) and nonsporulating bacterium. Cells are typically rod-shaped, and are about 2.0 micrometers (μm) long and 0.25 – 1.0 μm in diameter, with a cell volume of 0.6 – 0.7 μm3.
