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Observing Bacteria under a Microscope

For this science activity, we will be observing bacteria under the microscope. We will be performing this microscope activity in order to have more insight about bacteria. Knowing more about them can be beneficial especially to high school and elementary students, as the role of bacteria is significant in everyday life. What we need is a high power compound light microscope for this activity. Bacteria are very small, and can’t be seen with a low power dissecting microscope. Even when using the high power compound microscope, the higher power objectives need to be used.

Bacteria can be found almost anywhere but despite their abundance, it is hard to obtain one as we please. However, we can make our own sample of bacteria for our microscope activity with a few simple steps. The first thing that you need to do is to put some hay in water and leave it in a warm place. Make sure not to put it under a source of light. When the liquid turns cloudy or if there is a film forming on its surface, place a drop of its water (using a water dropper) on a microscope slide and put on the cover slip.

If you want to be extra careful in experimenting on these bacteria, what you need to do is to subject these samples to a sterlizing treatment. When you put the drop of water (thriving with bacteria) on the microscope slide, add few drops of alcohol on it and ignite it immediately with a match. (It is ideal that the teacher or someone who is old enough perform this process or else, the students should be very careful in handling the specimen.) This process will kill the bacteria immediately. Afterwards, add a few drops of methylene blue microscope stain (which can be bought at science stores or found in most any science microscope kit). When the specimen is soaked in the solution, wash the excess off with water and leave it until it dries. Once the stained spot has dried, we put Canada balsam on the edges of the cover slip. This will glue the cover slip in place and conserve the sample inside. Once you’ve done this precaution, you can now feel secure in experimenting with your bacteria under the high power biological microscope.

If you look at this drop of water under a biological microscope, you will see that it is swarming with bacteria. The majority of these bacteria are the Hay Bacilli and these look like rod-shaped bodies with single cells and length that are four times longer than its breadth. Let us focus on these microscopic bacteria using the fine adjustment knobs and you will see black dots. These are the spores.

Let us leave the liquid sample (where we took the drop of bacteria) for a couple of days longer and examine it again under the microscope (using the same treatment done to the previous sample). You will see that the bacteria has doubled and that there are once-celled creatures that move and feed with the use of their cilia. These are the infusoria and they are quite difficult to follow because of their rapid movement.

Once we are done with the hay bacilli, we can take another look at bacteria by cultivating it through another method. What we need is beefsteak broth and mix several tablespoonfuls of it with a small amount of gelatin and a pinch of baking soda. Boil a mixture and when the gelatine has melted, leave it exposed in a dish for at least an hour in ordinary room temperature. After that we leave it in a warm place for several days or until spots of different colors appear on its surface.

We use the same treatment like what we did in the previous samples with this sample before examining it under the microscope. When we look at these microscopic creatures under our high power compound microscope, we will also see bacteria in different shapes and sizes. There are more ways to obtain bacteria. The simplest way will probably be pressing you finger on a jelly and leaving it for some days in warm temperature. After this, you will already have samples for your science microscope activity. It is however vital to remember that after each experiment, we have to disinfect the area and throw away the slide. Bacteria can be harmful and often make us sick.

Observing bacteria can be very educational to students especially when they only think of these microscopic beings as only harmful to one’s health. The majority of known bacteria may perhaps be harmful but there are also some bacteria that are helpful to our lives and bodies. Some bacteria are responsible for the decay of dead plants and animals, and in doing so, they excrete compound such as water ad carbon dioxide that are essential to life. There are more bacteria out there that are helpful to our environment and, without our knowledge, even to our lives. Observing them with the use of our high power biological compound microscope can therefore be very helpful for us to get to know them better. Looking at bacteria is exciting for students and a highly recommended microscope activity.

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