Microscope

• The eyepiece, or ocular lens, is the part of the microscope that you look through to see the specimen.
• Microscope:

  • Contains more than one magnifying lens
  • Utilizes visible light
  • Magnification power (MP) up to 1000X the original size
  • Used to visualize bacteria and fungi
  • Specimen appears dark against the surrounding light
  • Less than 0.2um can't be visualized
  • Very low contrast
  • Ideally used to illuminate unstained samples causing them to appear brightly lit against a dark background
  • Contains a special condenser that scatters light and causes it to reflect off the specimen at an angle
• Refractive indices and light waves passing through transparent objects assume different phases

  • Contrast enhancing optical technique to produce high contrast images
  • Thin tissue slices, culture living cells, subcellular particles
• Nomarski interference contrast (NIC) microscopy:

  • Used to enhance the contrast in unstained, transparent samples
  • Developed by Polish physicist Georges Nomarski in 1952
  • Useful in examining specimens inhibited by standard staining procedures
• Fluorescence microscopy:

  • Uses fluorescence and phosphorescence
  • Used to visualize structural components of cells
  • Detect viability of cell populations
  • Visualize DNA and RNA
• Confocal microscopy:

  • Optical imaging technique for increasing optical resolution and contrast
  • Uses a spatial pinhole to block out-of-focus light in image formation
  • Useful in the study of cell physiology
• Electron microscopy:

  • Uses electrons to create an image of the target
  • Much higher magnification/resolving power than a normal light microscope
  • Inventor: Ernst Ruska
  • Represents 3-D structure
  • Image produced is black and white
  • MP: 10,000X - 2M times
  • Used to visualize viruses and subcellular structures of cells
• Scanning probe microscopy (SPM):

  • Forms images of surfaces using a physical probe that scans the specimen
  • Founded in 1981 with the invention of the scanning tunneling microscope
  • Used to study the molecular & atomic shapes of organisms
  • Used to determine the variation in temperature inside the cell
• Staining techniques:

  • Used to enhance contrast in samples at the microscopic level
  • Stains and dyes are frequently used in histology and medical fields
  • Focuses on the study and diagnoses of disease at a microscopic level
• Gram staining:

  • Differential stain used to differentiate between gram-positive and gram-negative organisms
  • Gram-positive cocci: Neisseria, Veilonella, & Branhamella
  • Gram-negative bacilli: Corynebacterium, Clostridium, Bacillus, and Mycobacterium
• Acid-fast staining:

  • Used to identify acid-fast organisms such as Mycobacterium
  • Acid-fast organisms have wax-like, impermeable cell walls
  • Ziehl-Neelsen Stain: hot method, acid-fast organisms appear red on a blue background
  • Kinyoun Stain: "cold method," acid-fast organisms appear red on a green background
• Culture media:

  • Aqueous solution with nutrients required for growth
  • Liquid, semi-solid, and solid media types
  • Agar is a common solidifying agent
  • Used to grow microorganisms
• Agar:

  • Obtained from red algae
  • Used in the laboratory to feed and grow bacteria and microorganisms
  • Acts as a culture providing nutrients for growth
• Media types:

  • Synthetic media: chemically defined substances
  • Non-synthetic media: does not contain any chemicals
  • General purpose media: supports the growth of both pathogenic and non-pathogenic organisms
  • Enrichment media: contains organic substances like blood or serum
  • Selective media: inhibits the growth of certain species of microbes while allowing others to grow
• Mannitol Salt Agar:

  • Encourages the growth of certain bacteria while inhibiting others
  • Used for isolation of Staphylococcus aureus
• MacConkey Agar:

  • Selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose
  • Inhibits the growth of Gram-positive organisms
  • Growth of Enterobacteriaceae
• Löwenstein-Jensen medium (LJ medium):

  • Growth medium used for culture of Mycobacterium tuberculosis
  • M. tuberculosis appears as brown, granular colonies
• Osteoporosis

  • Types of body movements and articulations
  • Bone fracture (compression)