The Measurement of Bacterial Motility

SUMMARY: Bacterial motility was measured by a simple method which consists of counting the number of organisms which pass across a small aperture in a given time. The count is proportional to the bacterial concentration in the suspension and also to the average speed of the bacteria. A slight increase in the viscosity of the suspending medium above that of a buffer solution has the effect of increasing motility; further increase in viscosity decreases it.