2. Viewing Microbial World

• Metric units


  Used to express the sizes of microbes

  
• Meter (m)


  The 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


  How far apart two adjacent objects must be before a given lens shows them as discrete entities
• Resolving power of the unaided human eye

  • 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
• Magnifying glass


  • A simple microscope that can make images appear 3 to 20 times larger than the object's actual size

  
• Leeuwenhoek's simple microscopes


  • Had a maximum magnifying power of about x300

  
• Compound microscope


  Contains more than one magnifying lens

  
• Compound light microscope

  • Usually magnifies objects about 1,000 times

  
• Resolving power of a compound light microscope

  • Approximately 0.2 μm (about 1,000 times better than the resolving power of the unaided human eye)

  
• Lens systems in a compound microscope

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

  
• Parts of a microscope

  • Mechanical parts
  • Magnifying parts
  • Illuminating parts

  
• Mechanical parts


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


  • Condenser
  • Iris Diaphragm
  • Light Source
• Magnifying parts


  • Eyepiece/ocular
  • Scanning objective
  • Low power objective (LPO)
  • High power objective (HPO)
  • Oil immersion objective (OIO)
• Total magnification


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

  
• Photomicrograph


  Photographs taken through the lens system of the compound light microscope

  
• 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

  
• Darkfield microscope

  • Uses a darkfield condenser with an opaque disc
  • Light reflected directly through the objective lens is blocked while light reflected at an angle is used to illuminate the specimen

  
• Types of Microscopes


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

  
• Light Microscopes


  Any type of microscope that utilizes visible light

  
• Brightfield microscopes


  Also coined as light microscopes