MBio Expt 4

  1. Type of microbe associated with water pollution
  2. Properties of coliforms
    • G--
    • Rods
    • Often found in intestines
  3. Examples of coloforms
    E. coli, Salmonella, Shigella
  4. Hoe do coliforms enter water?
    Usually through fecal matter
  5. How can selective media affect growth?
    • Addition of inhibitors
    • Change pH
    • Omission of nutrients
  6. Differential media
    • Contain specific growth indicators
    • Demonstrate presence of substances
  7. EMB Agar
    • Eosin methylene blue
    • Selective for gram neg
    • Lac Fermentors are blue
    • Lac Non-fermentors are colourless
  8. Two indicators in EMB
    • Eosin Y - Acidic
    • Methylene blue - Basic
    • The two dyes will react
  9. How do dyes generally work?
    Acid production causes uptake of dye; changing colony colour
  10. MacConkey media
    • Lactic acid fermentors (coliforms) turn red
    • Bile salts and CV inhibit G++ growth
    • Uses neutral red indicator
    • Production of bial salts
  11. Property of gas detecting media?
  12. Hugh and Leifson's method
    • Uses semisolid peptone media
    • Contains carbohydrate of interest
    • pH Indicator - Bromothymol blue
    • Stab inoculate
  13. Reactions to Hugh Leifson's method?
    • Facultative; Acid, Entire media turns yellow from top down
    • Using peptone only; Alkaline, blue colour only at top
  14. Motility media
    • Triphenyl tetrazolium chloride (TTC)
    • Semisolid, low [agar]
    • TTC reduction by microbe causes red colour
  15. Reactions in motility media
    • Facultative, motile; Whole tube becomes red
    • Aerobic, motile; Only top of tube is red
  16. What does IMViC stand for
    Indole, Methyl red, Voges Praskauer, Citrate
  17. Indole test
    • Conversion of Trp to Indole (in peptone water)
    • Kovak's reagent turns in pink in the presenc of indole
  18. Methyl red test
    • Mixed acid fermentation
    • Acid production lowers pH
    • { if (pH < 5) colour = red;
    • else colour = yellow }
  19. Voges-Praskaeur test
    • Butenediol fermentation
    • Non-acidic product
    • Test for Acetyl methyl carbinol (intermediate)
  20. Citrate test
    • Citrate is the only carbon source
    • Oxidative formation of NaCO3 increases pH
    • Grn->Blue
  21. Urea hydroysis
    • Assay for urease activity
    • Phenol red (violet->red) on pH increase (ammonia production)
Card Set
MBio Expt 4