UW-Stout/Acids SP23

Introduction

We are looking to find a pH that puts yeast under stress. Our end goal is to be able to test different knockout yeast strains against an acidic medium, but to do this we first need to find a pH that allows the yeast to grow, but puts some strain on the growth curve. In this protocol, we are testing wild yeast strains against different concentration of acetic acid. By analyzing the growth curves, we will be able to find a concentration that will stress the yeast growth.

Materials

• BY (wild type) Yeast
• 17.4 M Glacial Acetic Acid
• Deionized Water
• Sterile Water
• Pipettes
• 1.7 mL microcentrifuge tubes
• Disposable Gloves

Procedure

1. Using 17.4 M Glacial Acetic Acid, create a diluted stock solution

   • Use gloves when working with concentrated acid
   • Add 1.04 mL of Glacial Acetic Acid to 8.95 mL of Deionized Water

2. Using this stock solution, create further dilutions

   • In microcentrifuge tube, add 1 mL of Glacial Acetic Acid Dilution and label this tube 1
   • Take 10 uL of solution out of tube one and place in another microcentrifuge tube, labeled 2
   • Add 990 uL of sterile water to tube 2
   • Using tube 2, repeat this process to create tube 3
   • Repeat until there are 10 dilution tubes

3. Add 50 uL of BY yeast to wells 1-11 in the assay plate
4. Add 50 uL of each dilution to the well sheet

   • Add dilution 1 to well 1, dilution 2 to well 2, and so on
   • Use pipette tip to mix solutions

5. Add 50 uL of sterile water to well 11

   • Use pipette tip to mix solution

6. Set up plate reader as follows:

   • Temperature - 30 degrees Celsius
   • Mode - Kinetic
   • Wavelength - 600 nm
   • Interval - 5 min
   • Total Run Time - 24 hours
   • Shake Before Read - 30 seconds

7. Transfer assay plate to reader and read for 24 hours