Exam 4 final

• Tree of Life

  • Eukaryotes
  • Archaea (greater diversity)
  • Bacteria (most diverse)
• Viruses

  Cannot reproduce on their own, aren't always considered
• Only 1% of microbes can be cultured, meaning more exist but we can only culture so many
• Metagenomics


  Identify and characterize microbes that have not been cultured
• Microbes are ubiquitous, important for human health (virus = illness, bacteria and fungi = infections, bacteria can contaminate food and water), environment (microbes make oxygen and toxins → cyanobacteria)
• Sub-disciplines of microbiology

  • Ecophysiology
  • Bioremediation
  • Mycology
• Ecophysiology

  How the environment affects the physiology of microbes
• Bioremediation

  Using microbes to clean up the environment
• Mycology

  Understanding fungi (yeasts, mushrooms, etc.)
• Protists


  Any single celled eukaryote that is not a plant or a fungi
• Miasma theory


  Disease originates from particles emanating from decomposing matter, used to explain the Black Death
• Fathers of Microbiology

  • Antonie van Leeuwenhoek
  • Robert Hooke
  • Louie Pasteur
• Antonie van Leeuwenhoek

  First microscopic observations, observed protists and bacteria, named "animalcules"
• Robert Hooke

  Cell theory, observation of molds and fungi, cork
• Louie Pasteur

  Pasteurization, disproved spontaneous generation, swan neck flask, developed vaccines for TB, cholera, anthrax, and rabies
• Spontaneous Generation

  Decay of organic matter generates microbes
• Theories of life origin

  • Abiogenesis
  • Biogenesis
• Abiogenesis


  Life can originate from non-living material
• Biogenesis


  Living things only arise from living things
• Meat and flies/maggot experiment disproved spontaneous generation
• Germ Theory


  Microorganisms are the causative agent of disease
• Koch's Postulates


  • The suspected pathogen must be found in every case of disease and not be found in healthy individuals
  • The suspected pathogen can be isolated and grown in pure culture
  • A healthy test subject infected with the suspected pathogen must develop the same signs and symptoms of disease as seen in postulate 1
  • The pathogen must be re-isolated from the new host and must be identical to the pathogen from postulate 2
• Magnification


  The ability of a lens to enlarge the image of an object
• Total magnification

  = mag of object x mag of ocular
• Resolution


  The ability to tell that two separate points or objects are separate (resolving power = minimum distance to see two points as separate)
• Resolving power

  = wavelength of light (nm) / NA of condenser + NA of objective
• Want a smaller number, want a shorter wavelength = better resolution
• Increase NA = decreased resolving power = better resolution
• Optical microscopes

  • Bright-field
  • Dark-field
  • Phase-contrast
  • Differential interference contrast
  • Fluorescent
• Bright field


  When light is transmitted through a specimen, generally requires a stain
• Dark field


  When light is reflected off of the sides of a specimen, generally used when samples are sensitive to heat or drying
• Phase-contrast and interference

  Internal structures of live microbes, two beams of light
• Fluorescent

  UV light (shorter wavelength), staining with fluorochromes, excitation filter
• Confocal microscopy


  Constructs 3-D images from multiple 2-D scans of a specimen with a laser
• Electron microscopy

  • Transmission electron microscopy (TEM)
  • Scanning electron microscopy (SEM)
• Transmission electron microscopy (TEM)

  Looking at viruses and cell structure, electrons are transmitted through the specimen, thin samples
• Scanning electron microscopy (SEM)

  Detailed 3D images, sample is coated with metal and electrons are bombarded over it
• Staining

  • Simple stains
  • Differential stains
  • Structural stains
• Positive stains

  Positive charge, attracted to cell components, stains the cell
• Negative stains

  Negative charge, repelled by cell components, stains the background, used when cells are too sensitive to be heat fixed (cell membranes have neg. charge)