Microbiology

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Microbiology

• Lab Practices

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Care and Use of the Microscope
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The Microscope
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Parts

• Ocular lens (eyepiece)
• Tube (body)
• Arm
• Nosepiece and objective lenses(4X, 10X, 40X, and
  100X.)
• Stage, stage clips, and stage adjustment knob.
• Condenser and iris diaphragm
• Fine and course adjustment knobs
• Base and in-base illuminator.
• Light intensity control

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Objective lenses

• 4X scanning lens
• 10X low power
• 40X high power
• 100X oil immersion lens.

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• Course adjustment knob for focusing with 4X and
  10X.
• Fine adjustment Knob for focusing 40X and 100X

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Characteristics of light microscope

• Total magnification of a specimen is obtained by
  multiplying the objective lens times the ocular.
• Resolution (resolving power) Ability to show
  details. (0.2 micrometer for light, vary for
  electron microscope).
• Field of vision is the area seen through a
  microscope.

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Types

• Light microscope
• Electron Microscope

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• Light microscope
• - Bright field microscope
• - Dark field microscope
• - Phase contrast microscope
• - Differential interference microscope
• - Fluorescence microscope

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Light microscope

• Bright field---most widely used, specimen is
  darker than surrounding field.
• Dark field---brightly illuminated specimen
  surrounded by dark field.
• Phase-contrast---transforms subtle changes in
  light waves passing through the specimen into
  differences in light intensity, best for
  observing intracelluar structures.

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• Fluorescence microscope---modified compound
  microscope with an ultraviolet radiation source
  and a filter that protects the viewers eye.
• Uses dyes that emit visible light when bombed
  with shorter UV rays.
• Useful in diagnosing infections (syphilis,
  tuberculosis).

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• Electron microscope1- Transmission electron
  microscope TEM
• 2- Scanning electron microscope SEM.
• Forms an image with a beam of electrons that can
  be made to travel in wavelike patterns when
  accelerated to high speeds.

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• Transmission
• To observe internal cellular structures
• Highest magnification 1,00,000-1,000,000 X
• Resolution power 0.2 nm
• Allows the observation of viruses.
• Allows 2 D images.

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• Scanning
• To observe surface structures.
• Magnification power 10,000-100,000 X
• Resolution power 2,5 nm
• Allows the observation of viruses
• Allows colored, 3D images.

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Care and Use of the Microscope

• How to take care of the microscope.

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The Use of oil immersion

• The most important lens in microbiology is the
  oil immersion lens, It has the highest
  magnification and must be used with oil.
• The purpose is to decrease the refraction of
  light while increasing the amount of light
  directed into the objective lens, also enhances
  the resolution of the image.

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