Microbiology - L1 - Intro

  1. Discovery of Bacteria
    • led by the invention of microscopes
    • 1680s by Antony van Leeuwenhoek
    • Lens maker, Looked at plaque, drew different types of bacteria: Rod, Spiral, and Spherical shaped
  2. How many are there
    • 10^30 bacteria on Earth
    • 10^10 bacteria in human oral cavity
    • 10^8 bacteria in saliva
  3. Microbiome
    • collection of organisms that live in your body; different between individuals
    • Oral microbiome – collection of organisms that live in your mouth
  4. Biomass of bacteria
    • Half of the Earth’s biomass is made of bacteria
    • 1-2% of our body weight is bacteria
  5. Extremophiles (loving extreme conditions):
    High temperature =
  6. Low temperature =
  7. pH 1-5
  8. High salt
  9. Functions
    • Produce molecular oxygen (O2)
    • Recycling of nutrients (CNPS
    • Decomposition of dead organic matter
    • Prevent pathogens from colonizing (competitive exclusion)
    • Help digest food
    • Provide essential nutrients (B12)
  10. Scientific name of bacteria
    • Genus species
    • Staphylococcus aureus
    • Staphylo: cluster of grapes
    • coccus: sphere
    • aureus: gold
  11. Development of pure culture method
    • 1880s
    • Robert Koch/Walter Hesse (Fannie H.): isolate ind. bacteria species
    • potato wedges: not sterile
    • gelatin +beef broth in petridish: melt in incubator
    • agar + beef broth: final; still used today
  12. Colony
    homogeneous mass of bacteria from the division from one single cell
  13. Method of determining the concentration of a solution with bacteria
    • Limiting Dilution
    • serial dilution of 10-fold
    • test by 0.1ml per petri dish (needs to be included in the final dilution factor)
    • when too many colonies: lawn; not countable
    • goal is to have 20-200 colonies
    • Colony Forming Units (CFUs): one bacteria -?-> one colony; overlapping colonies reduce it...
  14. Microscopic features (shapes)
    • Sphere -> coccus; 1-2um
    • rod -> rod
    • spiral -> spirillum (short, curvy) and spirochetes (long, spiral)
    • Appendaged
    • Filamentous (long, thin filaments side-by-side)
  15. Filter sterilized solution
    • using 0.2 um filter
    • common bacteria can't pass (one exception, can squeeze through)
    • virus can pass through
  16. Gram stain was developed by ______, major application is for _______.
    • Hans Christian Gram in 1884
    • antibiotics -> G+, G-, or wide spectrum
  17. Gram staining procedures
    • Fixation
    • Stain w/ crystal violet: G(+) purple; G(-) purple
    • Treat w/ iodine: G(+) purple; G(-) purple
    • Decolorize w/ alcohol: G(+) purple; G(-) transparent
    • Counterstain w/ safranin: G(+) purple; G(-) pink
  18. Purpose of treating Gram stained samples with iodine
    crystalize the crystal violet to form insoluble clusters inside the cell, which is trapped and can't be washed out for G(+) bacteria
  19. Function of alcohol in Gram stain
    collapse the cell wall and wash out the color from G(-) cells
Card Set
Microbiology - L1 - Intro
Microbiology - L1 - Intro