- What is the meaning of motility ?
- What is hanging drop method ?
- How to do it ?
Motility – it is the movement ability of bacteria from one direction to another by their own. Some bacteria are motile and some are non motile.
Motile – means have ability to move
Non motile – means don’t have ability to move
So the question is why Hanging drop method is use to check motility instead using of normal slide method?
So the answer is- in normal slide motility of bacteria can be haulted by pressure of coverslip on slide. So to overcome from this problem Hanging drop method is used. In this cavity slide is used so the drop can be hang in cavity freely instead get presurised. In this tech. stains are not required. By using this tech. true motility can be observed.
Principle – Small drop which is taken on coverslip and make to hang in cavity of slide and observed under 100X i.e oil immersion lens shows motility of bacteria that bacteria is motile or not. If it is motile it shows specific directional movement and if it is non motile then it shows Brownian movement (vibrational movement occurs by the stricking of liquid molecules on each other).
Now lets see how to do test-
Requirements – Cavity slide , cover slip , Vaseline , 24 hour old broth culture of bacteria
Procedure – 1) first we have to clean the cavity slide and cover slip. It should be Greece free. Coverslip should clean slowly otherwise it can be break.
- Then add Vaseline drop on 4 corners of coverslip.
- Then take a loopful drop from our culture broth and place on covrslip.
- Then take a cavity slide and inversely place on
- Because of Vaseline coverslip will properly get fix on cavity slide.
- Then immediately invert cavity slide so that drop will hang in cavity.
- And immediately observe under microscope.
How to observe –
- First adjust the slide under 40X lens to observe edges of drop , once you find edges of drops then put a small drop of oil on the slide and then observe under oil immersion lens (100X).
- Stains are not used in this test so it is difficult to observe bacteria , so we need high resolution with enough light mean neither too much nor too low light.
- We can also see the Brownian movement i.e vibrational movement , so we have to ignore it and should focus on specific directional movement. If you see only Brownian movement that it means bacteria is non motile.
- And one thing should be done i.e immediate observation of slide.
(Note- immidiatly obseve slide before drying of drop).
Observation– In observation we get bacteria – 1) is motile or non motile
2) shape of bacteria
3) Arrangment –like in chain, cuboidal or in cluster form.
Paterns of motility – 1) Campylobacter shows Corkscrew like motility.
2) Vibrio cholera– rapid darting type of motility
3) Proteus – Swarming motility
4) Spirochaetes – bending and rotating body movement.
This is all about the motility testing by Hanging drop method.
Click to view the video of Hanging drop preparation