Microbiology- Microscopy and Staining

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Microbiology-Microscopy and Staining

• Microbiology
• Chapter 3, pp. 50-73.

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What is the smallest object ever seen?
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SPM of a Bacillus Bacterium
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SPM of Coccus Bacterium
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Carbon Atoms on Graphite
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Neon Atoms on Nickel
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What is light?

• Light is visible energy!

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Wavelength

• Length of a light ray
• Greek letter lambda

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Wavelength
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Wavelength
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The sun

• Produces a continuous spectrum of of
  electromagnetic radiation with waves of various
  lengths

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See it move
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Can other animals see other parts of the EM
spectrum?

• An Application
• Video- Discovery Vipers (Pit Vipers)

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Properties of Light

• Wavelength and Resolution
• Light and Objects

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How does wavelength compare to energy?

• An Application Video- The Blue Planet The Deep

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Light and Wavelength

• Length of a light ray- wavelength.
• Usually represented by the Greek letter ?.
• Sun produces a continuous spectrum of EM
  radiation.
• Visible light is from about ? 420 nm (blue) to
  680 nm (red).
• Fig 3.2, p 51.

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A. Resolution

• Resolution - the ability to see two objects as
  separate and discrete.
• A wavelength of light must be able to pass
  between the objects for them to be seen as
  separate.
• Shorter the wavelength, the greater the
  resolution.

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Resolution

• Visible Light (? 550 nm) has a resolution of
  about 220 nm.
• UV (? 100-400 nm) has a resolution of about 110
  nm.
• Electron Microscopes use electrons rather than
  light, e- ? 0.005 nm, resolution of EM is about
  0.2 nm

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B. Reflection

• Fig. 3.7, p. 56.
• Reflection- particular wavelengths strike an
  object and bounce back
• Reflected wavelengths give objects color.

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C. Transmission

• Transmission- passage of light through an object.
• Opaque objects cannot transmit any light.

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D. Absorption

• Absorption- when light rays do not pass through
  nor do they bounce back, but are used when light
  rays are neither transmitted nor reflected, they
  are absorbed.

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What happens to the energy of absorbed light?

• Energy from light rays can be used.
• Green leaf absorbs all wavelengths (except green)
  for use in photosynthesis.
• Energy from absorbed light is transformed into
  heat.
• Ex. Black car on a hot day.

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What happens to the energy of absorbed light?

• Absorbed light rays are changed into longer
  wavelengths and reemitted- luminescence
• Bacteria and other organisms can bioluminesce

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Two Types of 1. Luminescence

• a. If luminescence occurs after an object has
  been exposed to light - phosphorescence.

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Deep Sea Angler Fish
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Phosphorescent Bacteria in Lanternfish
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Show me Phosphorescence!

• Vibrio fischeri- a phosphorescent bacterium

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Two types of 1. Luminescence

• b. If luminescence occurs only while light rays
  are striking an object - fluorescence.

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Fluorescent Methanosarcina Bacterium
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Use of Fluorescent Antibodies to Stain Cells
(Bovine Pulmonary Arterial Endothelial Cell)
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Show me Fluorescence!

• Pseudomonas fluorescens- a fluorescent bacterium

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An Application of Refraction

• Video Built for the Kill- River

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E. Refraction

• Refraction- bending of light as it passes from
  one medium to another of a different density.
• Index of Refraction- a measure of the speed at
  which light passes through a material.

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A Magic Trick!

• Using the physics of light to make money!