26 Aug

Motility Determination

The motility of bacteria can be determined by several methods.  It can be determined microscopically by observing cells in a wet mount.  In this method a drop of cells is placed on a microscope slide and covered with a cover glass.  The slide is then observed with a phase contrast microscope.  It is better to use a phase contrast microscope for this application due to transparent nature of the bacterial cells.  The disadvantage of this procedure is that the cell dries out rather quickly which can cause problems if observations need to be made over a long period of time.  The second method is called the hanging drop technique.  In this procedure a drop of cells is placed on a cover slip which is then placed on a special slide with a concave depression in its center.  The coverslip is held in place with petroleum jelly.  This creates an enclosed glass chamber that prevents drying.  It is important to distinguish between cells that are moving due to the vibrations of the table and microscope and cells that are actually motile.