Friday, 20 January 2012


The hanging drop technique requires a few extra steps compare to the wet mount technique. The hanging drop technique is a more appropriate way to observe bacteria motility since the cover slip has a grove or a space for the bacteria liquid to be put on. After a few procedures, the bacteria liquid is observed using a compound microscope. Under a 10X magnification, there are no bacteria are visible except for a few particles.  The magnification is added until it was 40X. The image of bacteria is seen with less clear view because of the resolution.
There is a way to observe movement in bacteria. It is called the motility test. In this test, the motility media is stab with inoculating needle. This test is done to differentiate species of bacteria that are motile. The media and reagent used contains tryptose, sodium chloride, agar and a color indicator. There will be growth going out from the stab line if the bacteria are motile. If there is no motility, there will be no growth along the stab line.
There are two types of movement observed. The first movement is random and zipping across the field of sight. This is possible with the assistant of an appendage called the flagella. The flagella act as a propeller for bacteria to move in a rotation fashion, gliding and forward fashion. There are bacteria with single flagella and there are with numerous flagella disperse all around it. The example of motile bacteria is Salmonella typhymurium and E. coli.
There is another kind of movement observed under the microscope. This movement is different from the flagellated movement. It is not because of the bacteria itself rather it is the result of the bombardment of the bacteria by water molecule. This will create movement due to capillary action or convention current. It is the main problem when dealing with classification and identification of bacteria. Dead cells and nonliving particle tend to have this movement due from the phenomena stated. To overcome this problem, the motility test can be done( as stated above).
The second method is the simple wet mount technique. Under the 40X magnification, there is no movement or motility observed. This is because the bacteria are rendered motionless because the slit is pressed upon it. However, it is a weak hypothesis.
The hanging drop technique giver positive result whereas the simple wet drop technique gives no result. There are several factors that affect the outcome of the experiment. The main factor is the flaw in preparing the slide. The slit is not properly inserted. The bacteria solution is not properly administered. Some of the bacteria are dead but still shows movement
The haging drop technique is the most suitable method to observe motile bacteria.

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