Measurement of bacterial flagellar thrust by negative dielectrophoresis

The force produced by the flagella of the bacterium Salmonella typhimurium has been measured using negative dielectrophoretic methods. The bacteria ar e held in a force funnel, produced using a nonuniform electric field. When the motor force is balanced against an opposing negative dielectrophoretic force the bacteria become motionless. Numerical simulations have been used to estimate the electric field gradient in the electrodes. Together with ex perimental observations of bacterial motion the data gives a value of the f orce produced by the bacterial motor to be 0.37 pN.