A few words about microscopy

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A few words about microscopy

• Magnification
• Resolution
• Contrast
• Two- and three-dimensional imaging

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Compound light microscope

• Inexpensive and easy to use
• Uses visible light to view specimens
• Maximum resolving power is 0.2 µm
• Immersion oil reduces light refraction and
  increases resolution

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Resolving power

• Minimum distance between two objects that can be
  detected
• The shorter the wavelength, the greater the
  resolution
• Why do you get better resolution with an electron
  microscope?

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How do you increase contrast?

• Staining
• Different microscopes!

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Types of light microscopes
Phase-contrast
Nomarski DIC
Darkfield
Confocal
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Electron microscopes can achieve 100,000X
magnification
light
electrons
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Transmission vs. Scanning EM
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Scanning probe microscopes

• Can resolve atoms!
• Unlike electron microscope, does not require a
  vacuum or difficult sample preparation
• (Does require a lot of )

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Summary

• Microscopes are essential for the study of
  microbes
• Different types of microscopes allow for the
  observation of living and dead organisms and the
  structures within them
• Staining techniques increase contrast between the
  organism and the background medium

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Staining techniques

• Dyes
• Basic or acidic
• Simple or differential
• Can stain specialized structures on bacteria

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Fluorescent dyes and tags

• Can stain intracellular structures
• Can distinguish living and dead cells
• Can be used in quantitative analysis

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