MOTILITY TEST - BY HANGING DROP TECHNIQUE

 

 

AIM:

            To observe the Motility of the microorganisms under microscope by performing Hanging Drop Method.

PRINCIPLE:

            Bacterial cells have refractive index close to that of water, hence it is not easily observed in the unstained conditions. In Hanging drop technique, bacterial suspension is hung from the center of the coverslip into the cavity of the cavity slide. The motile bacteria moves towards the periphery due to increased oxygen tension and gravitative pull. They have an erratic movement in the surrounding medium with the flagella. One should be able to differentiate true motility from Brownian movement.

MATERIALS REQUIRED:

v Bacterial culture suspension

v Cavity slide

v Cover slip

v Petroleum jelly.

PROCEDURE:

1.    Take a cover slip and apply petroleum jelly on the four corners of the coverslip with the help of tooth stick.

2.    Place a drop of bacterial suspension on the center of the cover slip using a wire loop.

3.    Now take the clean grease free cavity slide i.e. has circular concavity in the center and invert the slide over the cover slip.

4.    Allow it to adhere to the jelly and slowly turn around the slide.

5.    Now the drop will be hanging from the cover slip.

6.    Observe the slide under microscope and focus the edge of the drop with 10X objective lens.

7.    Once the edge is focused, examine under 40X objective for motility.

INTERPRETATION:

            The given organism was found to be Actively Motile.

EXAMPLES:

            Motile organisms – Escherichia coli, Salmonella sp., Pseudomonas aeruginosa, Vibrio cholerae, Enterobacter sp., etc.,

         Non motile organisms – Klebsiella sp., Shigella sp., Salmonella gallinarum., Salmonella pullorum, etc.,