MICROLEC 2

• Metric units


  Used to express the sizes of microbes

  
• Meter (m)


  Basic unit of length in the metric system, equivalent to 39.4 inches
• Micrometer (μm)


  One millionth of a meter, used to express the sizes of bacteria and protozoa

  
• Spherical bacterium (coccus)


  • Approximately 1 μm in diameter
• Rod-shaped bacterium (bacillus)


  • Approximately 1 μm wide x 3 μm long
• Nanometer (nm)


  One billionth of a meter, used to express the sizes of viruses
• Viruses that cause human diseases


  • Range in size from 10 to 300 nm
• Ebola virus


  • Can be as long as 1,000 nm (1 μm)
• Ocular micrometer


  Used to measure the sizes of microorganisms under a microscope

  
• How many μm are there in 1 nm? ANSWER: 0.001 or 1 x 10-3
• How many μm are there in 1 km? ANSWER: 1,000,000,000 or 1 x 10^9
• How many nm are there in 10 m? ANSWER: 10,000,000,000 or 1 x 10^10
• How many cm are there in 100 μm? ANSWER: 0.01 or 1 x 10-2
• Microscope


  An optical instrument used to observe tiny objects that cannot be seen with the unaided human eye

  
• Microscope properties

  • Magnifying power
  • Resolving power
  • Contrast

  
• Resolving power of the unaided human eye is approximately 0.2 mm
• Robert Hooke first used a microscope


  1667
• Antonie van Leeuwenhoek used a single-lens microscope and observed "animacules"


  1675
• Zaccharias Jansen invented the first compound microscope


  1600's
• Joseph Jackson Lister developed a significantly better microscope


  1830
• Simple microscope


  Contains only one magnifying lens

  
• Leeuwenhoek's simple microscopes

  • Had a maximum magnifying power of about x300
• Compound microscope


  Contains more than one magnifying lens

  
• Compound light microscopes


  • Usually magnify objects about 1,000 times
  • Resolving power of approximately 0.2 μm

  
• Objects cannot be seen if they are smaller than half of the wavelength of visible light
• Compound microscope parts

  • Eyepiece or ocular lens (usually x10)
  • Objective lens (x4, x10, x40, and x100)

  
• Mechanical parts of a microscope

  • Base
  • Arm
  • Stage
  • Inclination joint
  • Body tube
  • Draw tube
  • Revolving nosepiece
  • Dust shield
  • Coarse adjustment knob
  • Fine adjustment knob
  • Slide movement knobs
• Illuminating parts of a microscope

  • Condenser
  • Iris Diaphragm
  • Light Source
• Magnifying parts of a microscope

  • Eyepiece/ocular
  • Scanning objective (4X)
  • Low power objective (LPO, 10X)
  • High power objective (HPO, 40X)
  • Oil immersion objective (OIO, 100X)

  
• Total magnification


  Calculated by multiplying the magnifying power of the ocular lens by the magnifying power of the objective lens

  
• Types of microscopes


  • Light Microscopes
  • Two-Photon Microscopes
  • Super Resolution Light Microscopes
  • Scanning Acoustic Microscopes
  • Electron Microscopes
  • Scanned Probe Microscopes

  
• Types of light microscopes

  • Compound light microscope
  • Darkfield microscope
  • Phase contrast microscope
  • Differential interference microscope
  • Fluorescence microscope
  • Confocal microscope

  
• Compound light microscope


  • Simplest and most common type of light microscope
  • Utilizes transmitted light coming from a condenser
  • Uses attenuation
  • Contrasts between acid and basic dyes

  
• Darkfield microscope


  • Uses a darkfield condenser with an opaque disc
  • Light reflected directly through the objective lens is blocked while light reflected from the specimen is used to create the image

  
• Light Microscopes


  Any type of microscope that utilizes visible light

  
• Brightfield microscopes


  Also coined as light microscopes
• Compound Light Microscope


  • The simplest and most common type of light microscope
  • Utilizes transmitted light coming from a condenser
  • Uses attenuation
  • Contrasts between acid and basic dyes

  
• Darkfield Microscope


  • Darkfield condenser with an opaque disc
  • Light reflected directly thru the objective lens is blocked while light reflected off the specimen enters the lens
  • Black background
  • Unstained microorganisms suspended in liquid

  
• Phase-Contrast Microscope


  • Sharp definition of cellular internal structures
  • Detailed examination of unstained live microbes
  • One beam of light
  • Two sets of light: from the light source and diffracted light from the specimen
  • Gray to black specimen coloration

  
• Differential Interference Contrast (DIC) Microscope


  • Differences in refractive indices
  • Two beams of light
  • Prisms split each light beam, adding contrasting colors to the specimen
  • Higher resolution than phase-contrast microscopes
  • Brightly colored and nearly 3D specimen