Many important physiological processes such as cell migration, biofilm formation, and pathogenicity require an understanding of the mechanism of cell motility. In particular, bacteria such as Escherichia coli propel themselves by means of rotating a set of flagella powered by 40 nm engines that are known as the bacterial flagellar motor. This bacterial flagellar motor, one of the largest and most complex biological rotary motors, is embedded in the cell membrane and exert torque on cells up to about 1000 pN·nm to navigate toward favorable environments in response to chemical gradients. However, despite extensive studies of the structure and the genetics of the bacterial flagellar motor, we lack sufficient understanding of how their torque generating protein components such as a rotor and stators function. Here, we investigate the relationship between the motor speeds and the number of stators involved in torque generation. Our results indicate that a single proton can generate torque required for a discrete angular step in the rotation of the bacterial flagellar motor.