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Growing Vita-Yeast

Pouring Dough Media

  1. Place a weigh boat on a top loading balance and tare the balance.
  2. Measure 2g of NaCl, using a plastic spoon to remove the salt from the stock container.
  3. Add the salt to the 100 ml bottle, and discard the weigh boat.
  4. Place a new weigh boat on the balance, tare it, and then weigh 3g of All-Purpose Flour.
  5. Add the flour to the 100 ml bottle that has the salt, and discard the weigh boat.
  6. Place a new weigh boat on the balance, tare it, and then weigh 1g of Agar or Gelatin.
  7. Add the Agar to the 100 ml bottle that has the salt and the flour, and discard the weigh boat.
  8. Measure 50 ml of water with the 50 ml conical tube and add it to the 100 ml bottle. Q: how does this recipe compare to the recipe for baking bread?
  9. Swirl the mixture for 10 or 15 seconds to try to mix the water into the powders as best you can.
  10. Screw on the cap to the 100 ml bottle VERY LOOSELY. If the cap is on too tight when you microwave the mixture, the pressure that builds up inside the bottle may break it.
  11. CAREFULLY: microwave the mixture for 20 seconds at a time, using a hot mitt to hold the bottle and swirl the mixture. It will remain cloudy and very likely lumpy.
  12. Microwave until the liquid that swirls around seems thick and hot.
  13. Pour the liquid into a petri dish or two, depending on how much was dissolved. Pour only until the bottom of the petri dish is covered. If you pour some lumps into the media, that’s OK.
  14. Cover the bottom section of the petri dish with the top and allow the media to solidify undisturbed on the benchtop, 30 minutes or so.

Restreaking Yeast

  1. Label your new petri dish with your initials, today’s date, the kind of media in the petri dish and the strain that you’ll be restreaking onto it.
  2. Start by dabbing the flat end of a toothpick onto a colony of yeast or bacteria that you want to restreak. The colony should be well isolated from the others and uniform in appearance.
  3. Transfer the cells from that toothpick by lightlying touch the toothpick to a spot on the new petri dish that you’d like to grow. Note: you should not break the surface of the agar with any of this procedure, but the results will still be OK, even if you do.
  4. With the flat end of a new toothpick, spread out the cells in the dab you made on the new petri dish by drawing your toothpick back and forth through the dab and then along the media in the dish. Do not back up as you draw since you are trying to spread out the cells that are on the toothpick from your one pass through the original dab of cells.
  5. With a new toothpick, spread out the cells still further, drawing from the ending line you made with the second toothpick. Again, do not back up as you draw with this third toothpick and try not to break the surface of the media.
  6. Replace the lid of the petri dish and incubate the plate media-side UP in an incubator (ideally 37° overnight for bacteria, 30° 2 days for yeast).

Liquid overnight cultures

VOCABULARY TO LEARN:

      “inoculate” = add a small amount of a material to get a starting reaction going.

“aliquot” = to doll out a portion of a material, sort of like a serving size.

 

  1. Examine the bottle of YPD to confirm that it is clear and nothing fuzzy or cloudy is growing in it.
  2. Label the two tubes with your initials, today’s date, and either “+cells” or “no cells.”
  3. Using sterile technique, place a 5 ml serological pipet in a pipet bulb or aid.
  4. Withdraw 5 ml of YPD into the pipet.
  5. Aliquot 2.5ml of media to each tube, replacing the lid of the tubes quickly.
  6. Dispose of the pipet in a waste container for sharps.
  7. Use a toothpick to scoop a colony of cells from the petri dish and throw the colony into the media in the tube marked “+Cells.”
  8. Replace the cap and grow the cultures overnight at room temperature or 30° on a rocker platform or roller wheel.
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