Abstract: The objective of the experiment is to learn how to use a microscope while viewing various types of bacteria cultures. Prepared slides are used to view bacterial cultures under a microscope that would normally be invisible to the naked eye. Bacterial shapes and arrangements or morphology are observed in prepared slides and fresh yogurt culture. Purpose: The experiment is meant to determine the shapes of bacteria under different magnifications when using a microscope; 10X, 40X, and 100X. A microscope must be used to see and study microbes since they cannot be seen with the naked eye. The different combination of microscope lenses allow for smaller organisms to be magnified and seen and studied in greater detail. Procedure: To view the yogurt culture, the yogurt has to sit in a dark warm place for 12-24 hours before it is viewed under a microscope. A small drop of yogurt is smeared onto the slide and a cover slip is placed over the smeared yogurt. The slide is viewed and observed under 40X and then oil lens 100X. First focus the low-power objective. Then, rotate to the medium-power and focus, and last use the high-power objective to see masses Data/Observation:
FreshYogurt Slide &
Prepared Yogurt Slide
Fresh yogurt has less bacterial growth
Prepared yogurt has separated purple rods or bacillus
Fresh Yogurt appears bubble-like in clusters
Photograph of fresh yogurt under 100X magnification
Photograph of prepared yogurt under 100X magnification
(A) The fresh yogurt appeared liquidities with moving liquid, like a stream of water. It showed clusters of bacteria. (B) There were observable differences between the fresh and prepared yogurt. The fresh lacked color and separated bacteria in comparison to the prepared yogurt slide. (C) Cocci are spherical and may remain attached after cell division, as seen in the fresh yogurt slide. Bacillus is rod shaped and can appear as single bacillus, diplobacilli, streptobacilli, or coccobacillus, as observed in the prepared yogurt slide. Spirillum has a helical shape and fairly rigid bodies and vibrio looks like curved rods. (D) The common arrangements of bacteria are: Diplo is two circle like cells sticking together. Strepto is more than two circle-like cells in a straight line. Staphylo is also two bacteria cells sticking together but in clusters. (E) The bacterial morphologies observed on the fresh yogurt slide are round or spherical bacteria. The prepared yogurt slide showed purple rod-like bacteria under the magnification 40X and 100 X oil immersion.
A. Identify the following parts of the microscope and describe the function of each.
A – Eyepiece
I. Fine adjustment
B – Main tube
F - Diaphragm
C- Revolving nose piece
G. Light source
K. Stage clip
D- Nose piece/ Objective Lens
H. Course adjustment
Define the following microscopy terms:
Focus: Is the image blurry or well-defined?
The focus is used to position the objective lens at the proper distance from the specimen. The image can be controlled with the focus knob if it is blurry.
Resolution: The closest two objects can be before they are no longer detected as separate objects (usually measured in nanometers).
Contrast is related to the illumination system and can be adjusted by changing the intensity of the light and the diaphragm/pinhole aperture.
B. What is the purpose of immersion oil? Why does it work? The oil immersion is used to increase the resolution of a microscope. Better resolution is achieved by covering both the objective lens and the specimen in transparent oil.
Conclusion: Cell structures in microbes vary tremendously in size and arrangements. For example, bacteria can appear in stands, clusters, or pairs. Also, bacterial morphologies differ, each with its own name. For...
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