observe_en.md

How to Observe Yeast

Items Required

• Plate growth medium with colonies
• Sterilized toothpick

For checking the shape:

• Microscope slide and cover glass
• Pipette and tip
• Pure water
• Biological microscope
• Digital camera

For checking fermentation:

• In a test tube, YPD liquid growth medium containing 10% glucose only.
• 1.5mL microtube
• Autoclave

Sample Procedure

Checking the shape:

1. On the plate growth medium, look at the shape and color of the colonies to determine how many kinds of yeasts there are. Use a toothpick to take a sample of each one. Take notes on which colony the sample was taken from.
2. Spread the sample on a microscope slide, use a pipette to add drops of pure water (2.5 μL or less without flooding the cover glass), and cover it with a cover glass.
3. Look through the microscope and take pictures. For yeast, the magnification should be around 60x.
4. Take a picture directly above the plate growth medium. If there is enough natural light, you can take pictures. If it is dark, illuminate with a side light before taking pictures.

Checking the fermentation:

1. For the YPD growth medium, prepare a liquid growth medium containing only 10% glucose.
2. Take samples from colonies on the plate growth medium and put them in the liquid growth medium. Incubate at 30°C.
3. Check for any carbon dioxide bubbles.

Checking the fermentation (using a microtube):

1. Immerse a 1.5mL microtube upside down into an uncapped test tube of YPD growth medium, then autoclave.
2. Take samples from colonies on the plate growth medium and inoculate them on the liquid growth medium. Incubate at 30°C. As time passes, the colony samples will drop to the bottom of the test tube.
3. Check for carbon dioxide accumulating in the tube.