Team:Queens Canada/Protocols

Protocols from key experiments for our project:

Materials

After the induction period, add guanidinium chloride to the induction culture to reach a final concentration of 0.8M
Incubate for 1-2 hours at 4°C prior to filtration
Withdraw 30-50mL of the Gdm-containing culture, then vacuum filter using 47mm polycarbonate filter membranes with 10um pores
Incubate the filtered biomass with 5mL of 8M GdmCl for 5 minutes
Vacuum filter, then rinse 3 times with DI water
Add 5mL of an aqueous solution (2uM MgCl2) of nuclease to the filtered biomass
Vacuum filter to remove the liquid then rinse 3 times with 5mL of DI water
Incubate the biomass on the filter with 5mL of 5% (m/v) SDS in water for 5 minutes
Vacuum filter, then rinse 5 times with 5mL DI water
Scrape the semi-purified curli from the filter paper with a flat spatula
Lyophilize, and store at 4°C

Inoculate 250mL of LB medium with PQN4.
Incubate at 37°C, 200 rpm shaking overnight.
Add 1mL of overnight culture to an 1L flask of LB media and incubate with shaking at 200rpm, 37C.
Incubate until OD600 of around 0.4-0.7 is reached
Before continuing, set up the necessary materials:

Once the cultures reach desired OD600, take them out of incubation and put them on ice for 30 minutes (the tube should feel cool).
From here on, keep cells always cool, at or below 4°C
After cooling, spin the tubes in a refrigerated (4°C) centrifuge for 30min at 5000rpm.
Pour off supernatant carefully, taking care not to pour off the pellet. If the pellet is not attached to the wall after centrifugation, smear the pellet onto the wall of the tube and centrifuge again using longer centrifugation times. Re-suspend bacteria in 500mL MQ water
Centrifuge again for 30 minutes at 5000 rpm and 4 °C temp
Pour off supernatant again, re-suspend pellet in 250mL MQ water on ice as before.
Centrifuge again for 30 minutes at 5000 rpm, 4 °C.
Pour off supernatant and re-suspend pellet in 10mL ice cold 15% glycerol solution.
Spin in 15mL tubes in large centrifuge for 15 minutes at 3400rpm, 4 °C
Resuspend pellets in 2mL of 15% glycerol mixture
Pipette 50ul aliquots into tubes. Label tubes properly.
Store samples on ice for immediate use or freeze 50ul aliquots in-80°C. According to some reports, the efficiency of electrocompetent cells reduces after each freezing, so immediate use may result in highest efficiencies.

CR stock: dissolve 1 g of Congo Red in 100 mL of water and filter sterilize. Store at 4°C.
Brilliant Blue stock: dissolve 1 g Brilliant Blue G250 dye in 100 mL water and filter sterilize. Store at 4°C. [brilliant blue increases the colour contrast of the colonies on the agar]
YESCA CR agar plates: 10 g/L casamino acids, 1 g/L yeast extract, and 20 g/L agar, 100 ug/mL antibiotic (for Amp; will vary depending on your antibiotic), 0.5 mM IPTG, 50 µg/mL Congo Red and 1 µg/mL Brilliant Blue. Autoclave only the dissolved agar and yeast extract, and filter sterilize the other components. Add the filtered components after autoclaved mixture has cooled.
Pick single colonies and streak out on a YESCA CR agar plate
To induce curli production, grow bacteria on YESCA CR agar at 26°C for 48 h
Check the color of the bacterial colonies. Wild-type curli-producing E. coli cells stain red on YESCA CR agar, whereas curli defective mutants are usually pink or white. E. coli mutants with hyper curli production sometimes stain dark red