Microbes are something that always exist in our surrounding even though we cannot feel their presence and see them with our naked eyes. To help us identify the microbes we can use a powerful tool; microscope. Microscope is use to enlarge tiny images such observing microbes so that they can be studied. The amount of magnification for a microscope can be enhanced up to 1000x to get a very clear image of the observed materials.
The light compound microscope contains two lenses which magnify a variety of image and knobs to resolve the image. Microscope can be used to enlarge the structure of bacteria and yeast. By using microscope, to get a clear characteristics; shape and type of gram of the stained bacteria, the magnification should be up to 400x or up to 1000x with the use of oil immersion objective lens. For yeast, it can be seen in unstained wet mounts of 100x magnification.
Besides yeast and bacteria, the microscope can also observe moulds, protozoa and algae. Mould mycelium and spores can be observed in unstained wet mounts of 100x magnification like yeast. Protozoa and algae are large organisms hence, they are readily visible at the magnification of 10x or 100x.
1. Identify all the parts of a compound microscope.
2. Know how to correctly use the microscope, especially the oil immersion lens and wet mounts.
3. Understand how microorganisms can be measured under the light microscope.
A. Using the microscope
1. Before the microscope was plugged in, the voltage control dial on the right-hand side of base of the microscope was turned to 1. Then the microscope was plugged in and turned on.
2. The slide was placed in the slide holder and centered it by using the two mechanical stage control knobs under the stage on the right-hand side of the microscope. A rounded drop of immersion oil was placed on the area to be observed.
3. The white-striped 100x oil immersion objective was rotated until its locked into place. This will give a total magnification of 1000x.
4. The voltage control dial was turned to 9 or 10. The iris diaphragm lever in front under the stage was ensured to be almost wide opened and the knob under the stage on the left-side of the stage controlling the height of the condenser was turned so that the condenser wall all the way up.
5. While watching the slide and objective lens carefully from the front of the microscope, the oil immersion objective was lowered into the oil by raising the stage until the lens just touched the slide. This was done by turning the coarse focus away until the spring-loaded objective lens just begun to spring upward.
6. Looking through the eyepieces, the fine focus was turned towards at a slow steady speed until the specimen came into focus.
7. By using the iris diaphragm lever, the light was adjusted to the optimum contrast.
8. After finished, the oil was wiped off of the oil immersion objective with lens paper, the voltage control dial was turned back to 1, the microscope was turned off, the power cord was unplugged and the cord was wrapped around the base of the microscope.
B. The prepared demonstration slides were observed.
C. Preparing a wet mount of baker’s yeast Saccharomyces cerevisiae
1. By using a pipette, a small drop of the yeast culture was put on a microscope slide and a cover slip was placed over the drop.
2. By using the iris diaphragm lever, the light was reduced to improve the contrast by moving the lever almost all the way to the right.
3. The specimen was observed using the oil immersion microscopy. The diameter of a typical yeast cell was measured.
4. Upon the lab completion, the oil was removed from the oil immersion objective using lens paper and the microscope was put away. The drawings of several of the bacteria from each of the four prepared slides were made and their approximate size were indicated in micrometers