microscopy and staining n.
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  2. Metric Units

  3. Light Properties • Wavelength

  4. polarity Light is a wave Filters can block waves in off axis planes

  5. Waves can be added + + = =

  6. Light Properties • Resolution

  7. Wavelength/Resolution Interaction

  8. Light Properties • Reflection • Transmission

  9. Light Properties • Absorption • Refraction bending

  10. Light Microscopy Types • Compound Bright Field

  11. Oil immersion Oil with intermediate refractive index without With oil Some info lost

  12. Microscopy — Dark Field

  13. Microscopy — Phase Contrast • Dual Beam

  14. Phase contrast • Phase-contrast microscopy was invented in 1936 by Frits Zernike, a Dutch mathematical physicist. It is based on the principle that cells differ in refractive index (a factor by which light is slowed as it passes through a material) from their surroundings. Light passing through a cell thus differs in phase from light passing through its surroundings. This subtle difference is amplified by a device in the objective lens of the phase-contrast microscope called the phase ring, resulting in a dark image on a light background (Figure 2.5b). The ring consists of a phase plate—the key discovery of Zernike—that amplifies the minute variation in phase. Zernike’s discovery of differences in contrast between cells and their background stimulated other innovations in microscopy, such as fluorescence and confocal microscopy (discussed below). For his invention of phase-contrast microscopy, Zernike was awarded the 1953 Nobel Prize in Physics.

  15. Microscopy — DIC • Differential Interference Contrast

  16. DIC “differential interference contrast” Similar to phase contrast, but input light is polarized

  17. Microscopy — Fluorescence • Ultraviolet light flourescein

  18. Advantages of fluorescence Can use specialized chemical probes that target specific features and then tag with fluorescent dyes Downside: must use expensive filters and excitory frequencies

  19. Microscopy — Confocal • Confocal Allows 3 dimensional viewing Allows multiple dyes to be overlaid

  20. Confocal microscopy Allows 3 dimensions

  21. Combined confocal and fluorescence Antibody labeling

  22. Microscopy Imaging • Digital

  23. Fig. 2-15

  24. Electron Microscopy • Transmission (TEM) • Scanning (SEM) • Scanning Tunneling (STM)

  25. TEM Most popular for bacteria. Allows imaging internal features, but requires heavy metal staining.

  26. Electron Microscopy Images

  27. Microscopy Techniques • Wet Mounts • Smears • Staining

  28. Fig. 2-3 Spread culture in thin film over slide Dry in air I. Preparing a smear Flood slide with stain; rinse and dry Pass slide through flame to heat fix II. Heat fixing and staining 100 Slide Oil Place drop of oil on slide; examine with 100 objective lens III. Microscopy

  29. Staining cells - increases contrast Simple stain - one dye - shows size, shape, and arrangement Methylene blue - yeast Cheek cell

  30. Common stains Safranin (*basic, + charge) red Crystal violet

  31. Differential stains Use multiple dyes or dyes that interact with organisms differently. Primary stain / counterstain

  32. Gram Stain • Gram Stain The single most important stain in microbiology. Set the initial taxonomy of bacteria. • Crystal violet *(basic stain)

  33. Gram Stain

  34. Acid Fast Stain Carbol-fuchsin stains acid fast organisms

  35. Acid Fast • The Ziehl-Neelsen stain, also known as the acid-fast stain, was first described by two German doctors; Franz Ziehl (1859 to 1926), a bacteriologist and Friedrich Neelsen (1854 to 1894), a pathologist. It is a special bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria. Mycobacterium tuberculosis is the most important of this group, as it is responsible for the disease called tuberculosis (TB). It is helpful in diagnosing Mycobacterium tuberculosis since its lipid rich cell wall makes it resistant to Gram stain. It can also be used to stain few other bacteria like Nocardia. The reagents used are Ziehl-Neelsen carbolfuchsin, acid alcohol and methylene blue.

  36. Acid Fast of Mycobacterium tuberculosis

  37. Negative Stain India ink or nigrosin Sometimes referred to as capsular stain

  38. Flagellar Stain Salmonella typhimurium

  39. Endospore Stain • Used on spore forming bacteria such as Bacillus sp. Malachite green stains spores