Making agar plates
- Mix 36.6 g/L of LB agar powder with MilliQ water in an Erlenmeyer flask (1 L flask for 500 mL). 500 mL will make ~20–25 plates
- Swirl so that there are no chunks left (it won’t fully dissolve)
- Cover with tin foil and put in autoclave set to the longest liquid setting (~45–60 min)
- After autoclaving begin to swirl periodically (~3–5min) to ensure it’s fully mixed and so the exterior doesn’t start to solidify.
- Once you can hold the bottom of the flask with a bare (gloved) hand add the antibiotic.
- Make plates at 100 ug/mL (e.g. 1 mL ampicillin to 1 L liquid LB agar).
- Turn on flame and pour agar onto plates – just enough to cover plate fully.
- Gently slide the plates off to the side of the bench (be careful because the plates will start to solidify and you don’t want them uneven) and let sit overnight.
- Use a marker to make lines on the side of the plate for the indicate which antibiotic was used.
- The next day put the plates back into the plastic sleeve holder, tape closed. Label the sleeve with the day the plates were made, antibiotic used, and concentratrion.