Commonly used technology in microbiology laboratory-microscopic examination

The microscope is an indispensable tool for studying microorganisms
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Since the invention of the microscope, people have been able to observe the forms of various microorganisms, and since then have revealed the mystery of the microbial world

The most commonly used in microbiology laboratories today is ordinary optical microscopes.
We must learn to use and maintain ordinary optical microscopes correctly
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An ordinary optical microscope is composed of two parts: a mechanical device and an optical system (Figure 4-3)

Figure 4-3 The structure of an ordinary optical microscope
(dashed lines represent optical systems, solid lines represent mechanical devices)

(1) Low-power observation

To examine any specimens under the microscope, it is necessary to develop the habit of observing with a low power microscope first
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Because the low power lens has a large field of view, it is easy to find the target and determine the location of the inspection

1.

Adjust the light source to turn the low-power objective lens to the working position, raise the condenser to fully open the iris, and then rotate the reflector to collect the light source.
Generally, it is appropriate to collect natural light from people, and direct sunlight is not suitable

2.
Adjust the numerical aperture of the condenser and the objective lens to be consistent.
Take off the eyepiece and observe directly into the lens barrel.
First shrink the iris to the minimum, and then slowly open it so that the aperture of the condenser is as large as the diameter of the field of view.
, And then put back the eyepiece, the purpose of this operation is to make the angle of the incident light expand to match the angle of the lens mouth
.

Otherwise, when the spot generated by the aperture opening is too large and exceeds the numerical aperture of the objective, such as to close the aperture is too small, the resolution is decreased, thus affecting the object image clarity, as each was

In actual observation, the aperture size is often adjusted only according to the brightness of the field of view and the contrast of specimen light and darkness, without considering the coordination of the condenser and the objective lens numerical aperture.

As long as better results can be achieved, this adjustment method is also advisable

3.
Place the specimen ascending lens barrel, place the bacterial staining picture on the stage, clamp it with a glass slide, and then lower the low-power objective lens so that the lower end is close to the glass slide
.

4.
Turn the coarse adjustment screw to adjust the focus, so that the lens barrel gradually rises until the blurred object image is seen, and then rotate the fine adjustment screw until the object image is clear
.

(2) High-power observation

1.
Find the field of view.
Displace the suitable part found under the low-power lens to the field of view
.

2.
To convert the high-power lens, press and hold the converter by hand and rotate it slowly.
When you hear a "click", it indicates that the objective lens has been turned to the correct working position
.

3.
When using a parfocal objective lens for focusing, just change from low magnification to high magnification, and then adjust the fine adjustment screw to see the object clearly
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If you use a non-parfocal objective lens, you must adjust the focus every time you change the objective lens, that is, first lower the objective lens to a position very close to the glass slide, and then slowly raise the lens barrel, and carefully adjust the coarse and fine adjustment screws until Until the object image is clear

(3) Oil lens observation

The working distance of the oil immersion objective lens (referring to the distance between the surface of the front lens of the microscope and the object to be inspected) is very short, generally within 0.
2mm.
In addition, the oil immersion objective lens of general optical microscopes does not have a "spring device", so use Be especially careful when immersing the oil objective lens to avoid crushing the specimen and damaging the objective lens due to inadvertent "focusing"
.

1.
Find a suitable field of view First use a low-power lens to find a suitable field of view, and move the part to be observed to the center of the field of view
.

2.
Change the oil glass to turn the oil glass to the working position
.

3.
Adjust the numerical aperture of the condenser and the oil lens to be consistent.
As long as the condenser is raised to the highest position and the iris is opened to the maximum, the numerical aperture of the two will be consistent
.

4.
Add cedar oil.
Take 1-2 drops of cedar oil from the inner vial of the double-layer bottle and add it to the smear on the part to be observed (do not add more), then turn the oil lens to the working position, lower the lens barrel, and make The oil lens is immersed in cedar oil and viewed from the side, so that the lens is lowered to a suitable position that is very close to the glass slide and does not collide with the glass slide
.

5.
Focus the left eye and observe from the eyepiece.
At the same time, turn the coarse adjustment screw to slowly raise the oil lens until a blurred object image appears, then use the fine adjustment screw to adjust until the object image is clear
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If the target object cannot be found according to the above operation, one possibility is that the oil lens has not been lowered in place, and the other is that the oil lens has risen too fast so that the eyes cannot capture the image of the passing object.

(4) Handling of the microscope after use

(1) Raise the lens barrel and remove the glass slide
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(2) Clean the microscope
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Clean the oil lens: first wipe off the cedar oil on the lens with lens paper, and then wipe off the remaining fragrance with lens paper dipped in a little acetic acid -alcohol mixture (V ether : V pure alcohol=2:3) or xylene asphalt, and then finally wiped clean lens tissue remaining xylene and the like
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Clean the eyepieces and other objective lenses: wipe them with clean lens cleaning paper
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Clean the mechanical part: wipe the dust on the mechanical part with a soft silk cloth
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(3) Set aside the objective lens
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Turn the objective lens into a "eight-character" >
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(4) Remove the cedar oil on the bacterial smear
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Add 2 to 3 drops of xylene on the smear to dissolve the cedar oil, and then gently press on the smear with absorbent paper to absorb the xylene and cedar oil
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This treatment will not damage the bacterial smear and can be stored for later observation
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If you don't need to keep the smear, you can boil it in soapy water and then clean it
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Related Links: Microbial Staining Technology