Name : See Yen Shan
Matrix number : 111415
1. INTRODUCTION
1.1 Ocular Micrometer
Ocular micrometer is use in order to measure and compare the size of prokaryotic and eukaryotic microorganisms. Microorganisms are measured with an ocular micrometer which is inserted into the one of the microscope eyepieces. The micrometer, which serves as a scale or rule, is a flat circle of glass upon which are etched equally spaced divisions. This is not calibrated, and may be used at several magnifications. When placed in the eyepiece, the line superimposed certain distance markers on the microscope field. The actual distance superimposed maybe calibrated using a stage micrometer on which parallel lines exactly 10μm apart etched. By determining how many units of the ocular micrometer superimpose a known distance on the stage micrometer, you can calculate the exact distance each ocular division measures on the microscopic field. When you change objectives you must recalibrate the system. After calibration of the ocular micrometer, the stage micrometer is replaced with a slide containing microorganisms. The dimensions of the cells may then be determined.
1.2 Neubauer Chamber
Neubauer chambers are more convenient for counting microbes. The Neubauer is a heavy glass slide with two counting areas by a H-shaped trough. A special cover slip is placed over the counting areas and sits a precise distance above them.
2. Objective
To measure and count cells using a microscope.
3. Result
3.1 Ocular micrometer
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| Ocular micrometer superimpose on stage micrometer under 400x magnification |
10 divisions stage superimpose with 40 divisions of ocular micrometer
10 divisions on stage scale = 10 x 0.01mm
= 0.1mm
10 divisions on stage scale coincide with 40 divisions on ocular micrometer
So, one ocular division = 0.1mm / 40
= 0.0025mm/2.5μm
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| Ocular micrometer superimpose on stage micrometer under 1000x magnification |
1 division of stage scale superimpose with 10 divisions of ocular micrometer
1 division on stage scale =1 x 0.01mm
= 0.01mm
1 divisions on stage scale coincide with 10 divisions on ocular micrometer
So, one ocular division = 0.01mm / 10
= 0.001mm/1μm
3.1.1 Lactobacillus measurement
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| Lactobacillus under 1000x magnification |
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| The zoom-in image of 1000x magnification of Lactobacillus |
The Lactobacillus cell is in 2 divisions, so the dimension is calculated
0.001mm x 2 = 0.002mm
= 2μm
3.1.2 Yeast measurement
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| The yeast cell under 1000x magnification |
There is total 3 division of the yeast cell, so the the calculation will be
0.001mm x 14 = 0.014mm
= 14μm
3.2 Neubauer Chamber
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| Standard hemocytometer chamber |
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| The Neubauer Chamber |
10 results from random picked square boxes : 34, 39, 36, 34, 43, 44, 40, 43, 33, 37
The average number of 10 boxes = 383/10
= 38.3 cells
0.004mm³ / 1000 = 0.000004cm³ = 0.000004mL 38.3 cells in 0.000004mL,
thus concentration of the cells
= 38.3 cells / 0.000004 mL
= 9575000 cells/mL
4. Discussions
4.1 Ocular micrometer
- The ocular micrometer is calibrated with the stage scale to count the exactly length of each division in the eye piece.
- Although the appearance of the ocular micrometer eyepiece will not change, but the stage micrometer will change with magnification. So there will be different value of one division under different magnification.
- Ocular micrometer does not have units on them, so the usage of ocular micrometer must be assigned with stage micrometer in order to get the the correct unit.
- The size of Lactobacillus and yeast are measured and the result is within correct range of the typical size of Lactobacillus and yeast.
4.2 Neubauer Chamber
- When the yeast culture is added into the space between coverslip and counting chamber, it must be slow so that i would not produce too many bubbles. The amount of the yeast culture should not be too much to make sure the coverslip is stable and it is not flow when we observe under microscope.
- The random-picked 10 squares from 25 squares should be avoided to pick from the outer squares.
- If an individual (one cell) locate in between 2 squares, it should be counted once only and counting of the same cell twice should be avoided.
5. Conclusions
5.1 Ocular micrometer
We can measure the exact size of Lactobacillus and yeast by using ocular micrometer. Lactobacillus is 2μm and yeast is 14μm.
6. References
We can measure the exact size of Lactobacillus and yeast by using ocular micrometer. Lactobacillus is 2μm and yeast is 14μm.
5.2 Neubauer chamber
By using Neubauer chamber method, the concentration of yeast cell in the culture can be derived from the data collected as well as counted.The concentration of the yeast is 9575000 cells/mL.
6. References
Thanks! This is very helpful :)
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