Lab Study Guide for Midterm

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  1. Simple stain
    crystal violet dye, methylene blue, safranin. Used to stain transparent cytoplasm so they are more visible under a microscope
  2. Basic stain
    "alkaline" positively charged chromogen which forms an ionic bond w/ negatively charged bacterial cell, thus coloring the cell
  3. Gram stain
    identify positive vs. negative bacteria, first crystal voilet, second iodine, third alcohol, fourth safranin.  Negative= red. Positive= purple
  4. Endospore stain
    Schaeffer-Fulton method of identifying spore forming bacteria.  First malachite green then steam bath for 10 minutes. Last safranin stain. Spores are green and vegetative and spore mother cells are red (REVERSE HOLLY leaf/berry)
  5. Standard plate count
    estimate population density in a liquid sample by plating a very dilute portion of that sample & counting the # of colonies it produces. V1D1=V2D2. End result is # of colony forming units
  6. MacConkey Lab
    selective & differential. contains lactose, bile salts, neutral red and crystal violet.  Red result=acidic/lactose fermenters. 
  7. EMB (Eosin Methylene Blue) lab
    selective and differential. contains peptone, lactose, sucrose, eosin and methylene blue. Lactose fermenters turn dark purple/black.  select for gram negative. E.coli=black accompanied by green metallic sheen.
  8. Phenol red broth
    differential.  contains peptone and phenol red dye.  Yellow result =acidic.  Pink or magenta above ph of 7.4.  Gas production = bubble in durham tube
  9. Blood agar lab
    B hemolysis= complete destruction of RBCs/hemoglobin ad results in a clearing of the medium around the colonies.  A hemolysis= partial destruction of RBCs/hemoglobin and produces a green color around colonies
  10. Mannitol salt plate
    contains mannitol, 7.5% NaCl, phenol red.  Yellow with yellow halo=acidic/able to ferment.  Red around neutral pH. Pink=alkaline. Selective & Differential.
  11. Citrate Lab
    contains sodium citrate as sole carbon source and ammonium phosphate as sole nitrogen source and Bromthymol blue dye.  As ph goes up the medium changes from green to blue.  Test evaluates organism's ability to break down CARBON. Blue = positive for citrate
  12. SIM media
    combinational media used for determination of sulfur reduction, indole production from tryptophan and motility.  Black precipitate indicates bacteria are capable of reducing sulfur.  Add Kovac's red, if shows red it is postive for Indole production. Positive motility=turbid.
  13. MRVP media
    combinational media containing peptone, glucose, and phosphate buffer.  used to detect bacteria positive for mixed acid fermentation.  Red= acidic (positive). Yellow= pH 6.2. 
  14. Starch plate
    contains beef extract & soluble starch. bacteria that are positive for amylase and capable of digesting starch are surrounded by a halo of a clearing AFTER being "soaked" in iodine.
  15. Gelatin lab
    Positve for gelatinase appears liquid. 
  16. Urease Lab
    differential.  contains urea, peptone, potassium phosphate, glucose and phenol red. Pink= urease-positive organism
  17. Nitrate reductase lab
    Gas in durham tube= denitrification. If no gas add Reagent A & B, if turns Red is positive for nitrate reduction to nitrite.  If no change add zinc, if turns Red at this point it means nitrate was not reduced by organism therefore is negative for nitrate reductase.  If no color change after addition of zinc it is positive for nitrate reductase.
  18. oxidase lab
    identify bacteria with oxidase.  positive will produce a purple-blue IMMEDIATELY
  19. Catalase lab
    Catalase converts hydrogen peroxide into water and gaseous oxygen.  Catalase positive bacteria bubbles immediately
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Lab Study Guide for Midterm
2013-11-01 14:10:00
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Important labs for midterm
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